Immune 55: Cells that suck at their job

from microbetv this is immune episode number 55 recorded on april 27 2022 i'm vincent dracaniello and you're listening to the podcast about the body's defenders against disease joining me today from ithaca new york cindy lifer welcome back winter's almost over here you know i i did a pod with someone in salt lake and they had 30 inches of snow in the mountains at the ski resorts over the weekend that's nuts we had a little flurries here this morning but it's it's warmer we had 85 the other day and then it's no it's very it's a very confusing time of year what was the word that someone used schizophrenic weather or something yeah yeah yeah we're like in third winter i think it's also joining us from durham north carolina steph langle hey there hey there not not in third winter here we're definitely in first summer so it was it was uh 89 the other day it's cool down a little bit we're in the mid 70s it's beautiful did you get new glasses stuff i did i did these are kind of clear lenses so you can see more of my face yeah but the red ones are very cool thank you i do like the red ones i'm trying to experiment more with glasses different colors different styles but the red ones could be used again right they're not absolutely sure no i'll i'll recycle i'll rotate them this is your husband's specialty right well this is the so this is my house and sound tracy you do get you know some access to cool glasses so you could wear a different pair every day right i maybe by now i could i don't know how many i have but yeah the clear ones are good i have a clear pair at the incubator that i used to just to see the screen and um the clear is cool yeah and also joining us from madison new jersey brianne barker hi uh it is uh i suppose middle spring here uh it's 53 and sunny today uh sometimes it gets a little summery sometimes it's still a little wintery but it's kind of nice today it's a little uh it's a little early springish right yeah that's fine at least the sun is out and now today i happen to be at columbia so i can look out the window and see white puffy clouds blue sky and uh it's what is it here let's see 13c that's very nice all right now today's my turn yeah to to lead on a paper and i'm just way out of my comfort zone here but i thought this paper was very exciting and um with the help of three bona fide immunologists we can get through the main points and um it is a an article in science you know it's i just noticed that it's got a heading corona virus it does yes so i mean there's a part of this paper that's coronavirus but it's not the main focus yeah not at all it takes over everything it does yeah it gets it published in science anyway the article title is cure plus cd8 plus t cells suppress pathogenic t cells and are active in autoimmune diseases in covid19 of course they put covet in the title right so it would get published for sure and so forth but i did like this dual aspect that they're looking at some mechanism of both autoimmunity and and infectious diseases and maybe there's a commonality there so i will do my best and my colleagues will help me out they they assured me they would help me out yeah we will we'll pop in and out you'll do a great thing we read it carefully in particular in particular cindy's going to tell us if the plots are actually real or not the difference differences i know that's your specialty comments yes i think we all might have comments on that one all right so my understanding is that for a while some cd8 t cells have been thought to suppress autoimmune responses everyone knows cd8 t cells do other things they can for example become cytotoxic t lymphocytes but some may suppress autoimmune responses and again my understanding is this was first uh determined in a mouse model of of multiple sclerosis which is called experimental autoimmune encephalomyelitis eae which i have to say i heard about in grad school which was in the seventies yeah yeah they were doing it for a while you're doing it for a long time and what the two things that you just mentioned speak broadly to uh a couple concepts in immunology so one being that you know we discovered cd4 and cd8t cells and cd4 cells are the helper cells and cd8 cells are the cytotoxic cells and they kill infected cells and what we now know with more technology better ways to define cells is that there's a there are heterogeneous populations within these big cd4 and cd8 classes which we'll talk about so that's one and two a lot of these uh heterogeneous populations these rare subsets are found in mice and it is really always the question of can we find these in humans do they express the same markers and single cell sequencing technology allows us to kind of get more into the weeds of that so i just wanted to bring that up that we're kind of touching on two two kind of big themes here yeah and so when i was reading this it made me think about some sort of of the history of actually some of those cd4 subsets a little bit um and how that was described and so some of this is um kind of what i've been told about uh the things that happened in the past of immunology um moving into some things that that i'm aware of i can talk about a little bit of how i learned something as an undergraduate and how that still stuck with me on that this front um because of this so i am told that there was a a uh hearty sort of study of t cells that could turn off other t cells um and potentially suppress other t cells um in the past i don't know exactly when that past was uh 70s 80s maybe they were known as suppressor t cells um and um those t cells were then shown to be or questioned in terms of whether they were in fact uh really relevant part of it was the relationship to a particular type of gene um in terms of some linkage studies that then when um genome sequencing happened there turned out to not be a gene there among other things and my understanding of what happened was that a fair number of immunologists were kind of like what suppressor cells oh no i never believed that um to the point where what i learned as an undergrad is that the word suppressor was a dirty word one of two words i was basically taught to not say and even now i feel like lightning is going to strike me down if i say that word as well as one other um and then as always happens they get reinvented yeah right rediscovered and given a different name and then that name was okay to regulatory cells so yeah and then there was this discovery um by sakaguchi uh some of the papers and uh by shivac of this cd4 subset the regulatory t cell because of course it's not a suppressor t cell it's a regulatory right yep um that's uh and so this is a cd4 type of cell that could um regulate or turn off other cell types um and it took a little while to have people fully kind of embrace the cell subset um first there was discussion of a particular cell surface marker cd25 that was on those cells and then um one of the things that became really helpful was a particular transcription factor that defined the lineage fox p3 was described and sort of this lineage of the cd4 regulatory t cell became t-regs this well-understood and well-known lineage that we have now but there has not kind of been a parallel set of cd8 cells um that has uh come around or been redescribed or re-understood in the same way that t-regs have been and so this paper to me is sort of trying to describe or start to get at a parallel cd8 type of cell and they talk a little bit about some experiments that they had done previously in mice trying to define such a cell type they talk about a particular cell surface marker the ly 49 marker on the cd8 t cells they talk about a particular transcription factor that might define the lineage helios um but the idea is now trying to find this same kind of unique regulatory cell um in humans and in in human situations and so to me it felt very parallel um to my recollection of that whole um t-reg story interesting and and also parallel when i went to start digging about this there's a lot of controversy about these li-49 cd8 positive t cells and what they're actually doing because there's evidence that they're uh you know cytotoxic and then there's evidence that they're regulatory that they promote disease or they inhibit disease and so i think that is very muddy and you know the the authors of this paper really referenced the work they had done that was pointing towards the regulatory phenotype and didn't really address the controversy i think yeah i when i was a grad student brienne i i remember the suppressor t cell story by richard gershon from yale and um you're right a lot of controversy and people didn't believe it and it went away i remember it went away and was reborn as t-rex yeah and unfortunately he he committed suicide and i don't know if it had anything to do with i didn't know failure but i know because his brother is here at columbia michael gershon he's still here and um yeah he um often talks about it yeah my brother working on disgrace he discovered them and nobody believed him that's true yeah true right i remember that so the um the the evidence starts in mice as brienne mentioned this these cd8 cells that have ly49 on their surface uh that's a marker for a set where they showed if you disrupt a co-receptor interacting with cd8 it they get spontaneous autoimmune diseases and so that was the implication of and helios is the the factor involved in the uh the differentiation of these cells subsequently found that these interactions don't just involve that original co-receptor which is called qa1 but also mhc-1 and so they're thinking maybe this has a broader relevance than intolerance so what they do in this paper is to identify killer cell immunoglobulin-like receptor keyers as the functional counterpart of ly of this ly49 hey we have another family today brienne yes we do have another family after the family we saw yesterday um so the ly 49 family is uh relatively well understood in terms of nk cells um so they're an important nk cell receptor um in mice right and nk cell receptors are known to bind mhd class one um so some um yes some of them yes um very confusing these are basically nk receptors that also are found on this group of cd8 t cells right so why are they not nkt cells right right i just i started as i was reading this i'm like we we no nkt cells are t cells with nk1k1.1 so this is a is a t cell with a different nk marker yes yeah i i actually was starting to to dig a little bit um in the nomenclature because i was like okay i know nk receptors and there and one of the important things is that there's positive receptors and negative receptors so and that comes to be important in this is that so these killer inhibitors they were originally called killer inhibitory receptors killer cell inhibitory receptors but you're right they changed it to immunoglobulin-like for the eye because then they discovered they're activating ones and so so some of these receptors are long and they have cytoplasmic tails and they're inhibitory but then some are short and they use a different signaling molecule and they actually activate the nk cell and so nk what's what we always teach about in k cells is they integrate positive and negative signals right and so if there's if there's no negative signal and there's only a positive signal that in k cell says okay i need to kill right and if it it receives a signal from the negative receptor it says i don't want to kill and that's going to come back to be important because these are cure receptors that are negative signalers right and so so that they say don't kill but then it it's really a balance because you could still have negative signals but if you upregulate the positive signals now you can kill or if if a virus for example decides to be clever and says i'm going to down regulate mhc class 1 to which as brienne said many of these cure receptors will bind to if they down regulate that the negative signal goes down and so it's sort of this balance between is there more positive or less negative you know where where are we and so the the nk cells integrate that information and i would say there's not much if anything known about these cd8 positive t cells that express these cure receptors and whether they do anything similar to that or whether they only express this one cure and how that contributes to everything that's going on so it's just something to keep in mind as we as we go forward talking about these all right so these secure positive cda positive cells they think are the the functional equivalent of the ly 49 cd8s and mice we're going to have some evidence for that and they think they have roles not only in autoimmune diseases and they look at several in this paper like celiac disease and but also in infectious diseases and they try and make a theory to wrap it all together but cindy's already said she doesn't buy it so that's fine actually i completely didn't buy it you know i i think we actually should step aside for a second though and talk about celiac disease because i think that's a really interesting immunological thing um so celiac disease is a true gluten allergy and i always mention this because we hear so much about gluten and gluten is bad and people want low gluten diets or gluten free diets and and really i don't i've not heard much that it makes much of a difference other than if you actually have a gluten allergy and the gluten allergy is because the gluten is a complex long molecule that gets chopped down into these monomers that are called gliadin and they that can be transaminated by by this enzyme are transcontaminated by this enzyme tg2 and what that does is it makes a peptide and if you don't have the right mhc that combine that peptide it doesn't matter for you you're fine you just digest gluten you have no problem the problem is that certain people who have a particular mhc molecule called hla dq2 specifically combine that deaminated gliadin peptide in the mhc and for some reason those t cells were not tolerized during development or or eliminated during positive you know negative selection and they're available and they can recognize that mhc and then they can cause disease and they can also induce antibody production then you get antibodies to the gluten molecules and basically it causes a pretty serious inflammation in the gut and basically a failure to obtain nutrients because of the inflammation in the gut so these these babies that have this disease they start to have failure to thrive and that's how you usually identify this gluten allergy um and yeah it's a very highly genetically um linked disease because 90 of the individuals who have celiac disease have that hla dq2 right so it's very highly linked and so the solution is to not eat gluten not eat gluten right right okay i think from looking at this paper one thing that cindy mentioned that's super important is the role of inflammation in celiac disease because i think a lot of the situations that they're trying to tie these cells to all have inflammation as an underlying absolutely right yeah absolutely okay all right so ly49 and these keyer receptors bind class 1 mhc which have these inhibitory motifs as that cindy mentioned in their cytoplasmic tails itims right so they're on nk cells and also a small number of cd8 positive t cell so they said okay let's look in the blood of people with autoimmune diseases at the cd8 cells with with these keyers so they have a cohort of patients and age and gender matched healthy controls and they um they look for these the cure on the surface of these cells and they find that the frequency of cure positive cda positive t cells is increased in the blood of patients with multiple sclerosis sle systemic lupus erythematosus and celiac disease compared with the blood of healthy controls all right so the first hint ah this population is is elevated is that new did we know that before i don't think so i don't think so because they have yeah this particular cd t cell subset no but it is interesting to look at the variation in those percent positive mm-hmm uh curiosity cells because the the significant difference as i almost ignored just because they're really driven by some individuals with really high percentages of these cell types and if you were to take those away would that really be significant and there's quite uh you know looking at like the sle there's a lot of individuals that are at the same levels as the healthy controls and then the ms patients there's about half the number included in terms of total patience so i think we could say certain individuals and i would like to know you know are they actually undergoing some type of inflammatory response due to their disease but it it as with all human studies and again this is when you're trying to translate human to mouse to human there's so much variation in humans and so you that that is really showed here so they did try to ask that though right because they they took ones in active celiac and in remission yeah in the next part and they try to suggest that you know it's higher but here's my thought question and this is where i was stuck with this whole paper if you have an inflammatory disease and you go to measure inhibitory cells would you expect them to be higher or lower in an inflammatory disease i would have thought they would be lower because so the other problem is if you do have more of them they must suck at what they do right yes because they're clearly not reducing inflammation or maybe they are but then the the way they reduce it gives you more more information that's true too so this reminded me of a an argument that i used to have with my phd advisor um because we used to have this argument about cd8 levels of cd8 cells in response to virus and would you expect to have a lot of cd8s when there's a lot of virus or a lot of cd8s when there's a little virus um and we but we could basically argue either side of it that maybe if you have a lot of cd8s when there's a lot of virus because the large amount of virus would increase the amount of cd8s or maybe you have a lot of cd8 when there's a little virus because a lot of cd8s got rid of the virus and so we we sat and argued that point back and forth sometimes and i kind of saw this as being something similar that perhaps the excess inflammation was driving the production of these cells but you're right there don't seem to be doing everything they need to be doing well and it's interesting if we think back to so tim hand had come on the show and he had talked about his paper looking at environmental enteric neuropathies of children and his story was that enteropathy uh caused an enhancement of tgf beta positive t regulatory cells and so then the cd4 t cells that were going to respond to the vaccine could not do so right because of this issue and so yes it is i think you have to consider the context of the disease and what is that driving um what type of response yeah so i wondered whether it was the inflammation was driving the cells but the cells you're right were maybe less effective at turning that inflammation back off so this this study was done with blood cells so then they say what about the tissues that are inflamed in these diseases so celiac disease the gut kidneys for sle rheumatoid arthritis patients synovial tissues and there they also find elevated levels of these cure cd8 cells so that's a question on this and and one cindy i agree with you i'm glad they did a b which which they did do normal remission and active celiac so you could see the different states but for for c and d so uh and particularly in d the number of away individuals at least in the they actually have it switched but it says it's n of three but when i look at how many dots are on this graph so are they showing us single cells it does not tell us how many how how many patients are represented here there's tons of dots but only three patients they say yeah yeah i found those super confusing uh yeah i understand what they did and when you look i tried to figure it out they don't really describe my assumption is that these these dots represent single cells because how else could there be that many dots for an n of three but um how many patient samples are represented would be really is it one patient single cell data so i mean it still shows the same trend that in the in the individuals with the disease that's when you see the expression but it's a little hard to tell how many what the n is here by the way i forgot to tell you that this is mostly a group at stanford university yeah i mean it's mark davis it's a great immunology group yeah he's a fantastic amazing um and the first author is jingly so this department um microbiology uh where mark davis is uh i uh i had an offer from them when i was looking for jobs and mark davis had just moved there as well and they use oh mark davis is here you should come but i didn't i decided to come to colombia there's too many decisions too many palm trees well there was no virology out there frankly yeah yeah anyway so next are these cure cd8 cells functionally equivalent to ly 49 cd8s and mice and they had previously found that these ly 49 cells can suppress pathogenic cd4 cells that are recognizing a particular protein myelin oligodendrocyte protein using perforin right a perforin which would be released from the cell which would poke holes in the membrane in this case of the cd4 cell and eventually make it undergo apoptosis kind of like what cd8 ctls do right correct so as cindy said this deamidated gliadin from gluten is the antigen for cd4 t cells that drives celiac disease right an autoimmune disease so they asked can cure cdh cells suppress gliadin specific cd4 t cells from celiac patients so they got peripheral blood mononuclear cells from patients cultured them and with or without gluten and without cure positive cd8 t cells you get stimulation of expansion of these cd4 gliadin specific cd4 cells um and then if you add stimulated cure plus cd8 cells but not cure minus or cure nk cells you reduce the number of these gliadin specific cd4 t cells so tell me when they say stimulated what are we doing to stimulate them so antigen presenting cells have to be present and they're going to take up the dminated gluten or gliadin and they will present it in the context of mhc class 1 or a class 2 sorry in this case for cd4 t cells and those cd4 t cells will get their signals that they need to to react and then they'll expand in vitro and they detect them with what we call a tetramer so that's a way to it's a basically a synthetic mhc class one molecule with the correct peptide and and you can incubate it it's fluorescently labeled and it's connected okay stuff and and then so it labels the antigen specific t cell so they're they're not showing you all the other t cells that could be there that maybe do or don't get expanded but but the antigen specific t cells are there if you um if you don't have the cure cd8 t cells but they're not there if you do have the care cda t cells and so i guess what i was wondering is are they are they killing them or are they preventing them from expanding and that wasn't entirely clear to me from this particular experiment because although the only readout is at the end of however many days they're asking are those are those cells present or not right right and we'll get to it but do you think the next experiment with the nexon answers that question so they yeah so the question then is you know were they did they expand and then get killed um and if so how or did they fail to expand and so one way to ask that is you you look for a a marker of cell death and so cda t cells like you said have perforin and they carry granzyme and basically poke hole and they deliver granzyme into the cytoplasm and granzymen is an enzyme that induces uh cell cell death autonomous cell death and so that's how that's how we'll undergo packaging of its components into little bits and spit the bits out and it basically degrades itself and one of the first events that happens is lack of maintenance of the plasma membrane structure and uh lip phospholipids that are called phosphatidylserine are usually only present on the interlea inner leaflet of the plasma membrane and when the plasma membrane integrity is lost it flips to the outside and an xn5 will bind to that and so you can detect those cells that are basically undergoing apoptosis or a cell death these cure cd8s did not recognize influenza virus hemoglobin in specific cd4 t cells which you to which you've added peptides so they seem to be specific for these pathogenic cd4 cells and the the support they call it suppression of expansion they say this is contact dependent because if you separate the cells with a membrane it doesn't happen yeah in half and half it was abrogated yes right yes of course so it's not zero right right if you draw that line above the unstimulated i'm like oh look 50 percent yes well that's biology right yes of course yeah they also found anexin binding on these um gliadins t cells uh in the presence of the cure tdh cells which they suggest shows that they can induce apoptosis of those cells as as cindy has just been saying yep so from this they conclude these cd8 cells suppress the pathogenic cd4 cells in this case the gliotin specific ones by direct killing and they also do an il-12 experiment an il-2 experiment where you add a lot of il-2 and the killing still happens so they say it's direct killing instead of competition for il2 can can you explain can we go over that experiment so so yeah what they're saying is il-2 are they saying because il-2 can also stimulate cd4 t-cell into t regs i mean that is one of the cytokines so they're trying to compete no i think it's so brian you may comment on this but so t regulatory cells have multiple mechanisms to suppress expansion of effector t cells and so some of those include direct contact some of them include fast and fast ligand-mediated cell deaths um and one of the ways is either competing for nutrients or degrading things that they might need and one of the things is il-2 so the the t-regulatory cells can kind of if they're in high numbers stop up the il-2 and then there's limiting amounts of il-2 so the cd4-t cells need a lot of il2 and they can't can't proliferate as well but there are a lot of there are a lot of other mechanisms as well yeah yeah so i've heard of that mechanism of particularly with t-regs because of their cd25 expression as them being uh cytokine sync or basically just sync just soaking up all of the il2 so that the other potentially pathogenic cells don't have any um and so the idea here is they're showing that if they add so much il2 that it could not be competed away that the the cytokines sink cells could not possibly sync it all up um the um the it doesn't rescue yeah the the expansion is still blocked so it wasn't just that all the il-2 got used up because if you put in so much aisle too that you could yeah it still is still a problem got it all right next they say we know that the the ly49 cells their activity in mice is mediated by both classical and non-classical mhc-1 so and in fact the the t-cell receptor is is required to fully get suppressive function they show that in an experiment plus if you add antibody if you blockade hla either abc or e this partially reverses the suppression caused by the the cure cd8 t cell so they say it's through recognition of both classical and non-classical class one like the ly 49 in the mice so they're trying to draw that correlate corollary between the two it's really weak though well [Music] yeah i even look at i mean it's just not again clear to me um right that these differences are biologically relevant and then there's other mechanisms that they could have tested then they do rna-seq analysis on uh cure positive and cure negative cd8s from their ms patients and they compare them to similar studies done on ly cd8 cells in e-i-e-a-e mice and they have you know lots of genes that are up and down and i won't go through them unless anyone wants to but basically that they show that the the cure cd8s and humans and the ly 49s and mice share a lot of similarities in terms of upregulated genes right and i guess there was i think one line that said there was a hundred of the 200 degs which is differentially expressed genes a hundred of them were shared between the two and i just was like okay is a hundred like what's my threshold for thinking of a cell that's that the same is that enough to yeah i don't know i i thought about that too because uh there's so much of this gene expression analysis now especially the single cell level and you you want to ask you know how similar do they need to be to be called the same thing i i will say that from looking at thinking about memory cells between a mouse cd8 memory cells versus human cd8 memory cells the markers are not always the same so i was actually kind of impressed so you're like okay this is actually good there were a couple things where i was like oh wow you got both of those markers to do the same thing in mouse and human that's amazing oh interesting so again it is kind of that context depending you really you have to be redundant in the way you prove this you have to prove it by single cell you got to prove it by the function and then you can holistically say okay these are similar i think that you know what what was more impressive rather than the number were the types of genes that were shared right they did do pathway analysis they did do you know some some analysis of that and it it was more like the cytotoxic genes that these types of cells use to kill cells you know or induce apoptosis in the cell so those are the kinds of things that one would hope would be shared if if they were having the same function yeah and vince that you may be going into this next i didn't know the part where they discuss high or low expression of are you going to talk about that next or was that a part of the part you were going to move over because i just wanted to ask a question about that um i was going to mention this this idea of uh and hit both inhibitory and and activation and effector is that probably you go ahead and then we'll all i was going to say they took the data from this because they know that these cure cells have these inhibitory items right so they wanted to know how that how that plays into the the differentiation so they looked at high and low keyer uh markers and they conclude that the high expression of these inhibitory receptors is suppresses activation and effective functions to allow precise control of their activity to avoid bystander suppression so i don't understand what that is maybe you can explain that well that's where i was a bit confused because i think they described that the the low expression were the cytotoxic cells but then in other experiments they're they're demonstrating that these cells are indeed they're killing by perforin for example which is absolutely toxic so i guess that's me maybe the nuance that we're missing here is because of the first experiments they did not separate out function based on high or low expression they just put them all together correct which could have be the reason why the variation was quite high that would be my guess yeah i you know they so the data that you're we're you know skirting around here is looking at covered patients right so that's that's where the coved stuff comes in and you've got severe disease moderate disease or mild disease and it the the expression of the cure on these cd8 care t cells actually goes down as severity increases and so the argument is that the cures are inhibitory the particular one that's expressed is inhibitory and so it is surprising which is how we started this like how do we wrap our heads around this entire paper how can you have these cure cd8 cells but yet they're able to eliminate cells if they're expressing an inhibitory receptor and the argument is that if they have very high levels of inhibitory receptor they are um not killing a lot of things but if they down regulate it now they don't have as much inhibition and they can kill but then i still have the problem that if you're killing the auto active cd4 t cells that are causing a problem shouldn't they be less in the more severe but then you come back to the argument that brienne was saying was you know is it the chicken or the egg are they there because yeah they need to do their function or what yeah so um steph did you want to ask something about that that was that was actually exactly good right yeah that was just the question of high and low expression did i did i summarize what everybody is thinking or did you guys think something different yeah i didn't talk about that i was going to ask you that because i thought it was a naive view of what's going on because yeah you're absolutely to me anyway yeah i i think that um the idea of remembering that these are inhibitory receptors and so um having lots of them would inhibit cytotoxicity is sort of that key point that one has to keep remembering right but if the if the argument is that these care cd8 t cells are are blocking autoimmune pathology then one would think that the the more functional they are the less inflammation and autoimmune immunity will have right but it seems to be the opposite so that's where i keep getting stuck because that was kind of the synopsis of their first experiments with that these cells have more function they're killing their well we don't know killing or not letting proliferate the cd4 t cells but now with the covalent patients right that that that paradigm we've maybe set up gets a little muddy yeah i i think that the thing that that i i get stuck on is something from a little bit earlier in the paper and this just sort of it hurts my brain and sort of can't move past it is they show earlier um that they they don't have an effect on um the influenza specific cd8 c4 cells that are expanded and so those are expanded activated cd4 cells yeah so the implication here is that these these cure cd8s these suppressor cd8s are whatever we're gonna call them know the difference between bad guys and good guys in terms of cd4s i wonder though are you so is that also your statement in the context of the covet data well so so but then but i think that that's what especially if you look at the at the very beginning of the paper and sort of the graphic abstract they they show the cell only um inhibiting the ones that have strong reactivity to self not the ones with weak reactivity itself they they sort of imply there that there's this differentiation between or distinction between is this an appropriate or an inappropriate response and so i think the idea would be well in the severe patients it's an appropriate response because you need to get rid of virus and in the less severe patients that's an inappropriate response but i still don't know how how the how the t cell knows who's a good guy and who's a bad guy i that that just my mind's blown i mean maybe maybe when you have an acute viral infection the t cells that you're um bringing in to the response are going to be the highly reactive foreign you know against foreign molecules and so they would have very low autoreactivity right whereas if you have this low simmering right but then how chronic inflammation how do the care cells know which ones they're supposed to inhibit and which ones they're not supposed to inhibit well that is it right that's a why question that's what that's where i like this i got it i don't know but do you go ahead that's what has to be figured out right how do they distinguish yes well and so we can think about the influenza experiment because those cells were not derived in an environment where influenza had caused severe disease i think the distinction is severe disease causes a lot of cell death a lot of damps a lot of secretion of self where as a cure cd8 positive t cells would be beneficial in that situation because you have so many more autoreactive potential i think the influenza experiment is just there weren't enough self it wasn't from a severe influenza patient would be my assumption where as well so it could be timing right well yeah for sure because i think an acute an immune response to an acute viral infection is going to be different than as the virus goes away and the immune system is causing the damage which is why i think in the coconut patients correct more sensitive that second part is where you're going to have more of those autoreactive t cells so maybe it doesn't know necessarily but it's a timing thing like when those cells are are proliferating that's when they're going to be functional i don't know and then the celiac experiment that the with with the glead and that actually worked because it was from celiac patients where the inflammation the inflammation happens so yeah all right so next they look at infectious diseases and their idea is that so so you know the old view is that during thymic development you get rid of self-reactive t-cells but we don't that doesn't always happen then you end up with self-reactive t cells and that's partly why you have autoimmune diseases but they say we think this is important this happens because you need a big t cell repertoire to deal with infectious diseases so you don't want to get rid of some of those potentially self-reactive i don't know what do you think that makes sense you guys yeah is that good yeah that is how i teach that yeah interesting right you have to have a little bit of leakiness of autoreactive t cells because they could be cross-reactive to sure and when you're doing selection in the thymus given that you're selecting on kind of the whole surface of mhc plus peptide yeah it's really hard to get that selection perfect yeah yeah okay so they they look at covet patients they have 53 patients and they say these key ocd8s are substantially elevated in many of them and they the higher levels correlate with more severe disease so highest frequencies are in patients with vasculitis or embolism acute respiratory distress syndrome all of which are caused by excessive inflammation right so this gets back to what cindy was saying oh they're working why are they so high they did not see differences in other anti-rags of a certain type for example or any cure and k cells right but they did find an increased frequency of these cure cd8s in peripheral blood of influenza patients so they say well maybe they are induced as part of the response to infectious diseases as well as uh you know auto immune diseases what do you think about those those sets of experiments i don't i don't know but i think that it's interesting people have often had uh the suspicion that viral infections might precipitate autoimmune disease and this might provide some explanation for how that might happen right so that part that part i liked i think that there's still small numbers yeah and it you know some people think that part of long covet is autoimmunity so correct would be interesting if it's correct right maybe maybe suggest some treatments right so seeing some these cells in long covet patients would you find them to be higher yeah that's a good do have people look do you know i think this is the first paper on said sells so no yeah i think it's the first one yeah yeah they're probably collecting the data yeah all right the next section i'm very fuzzy on they did our single cell rna-seq on cd8s from healthy controls ms patients covet patients um and look at single cell gene expression levels to see you know is there something in common amongst these cells in dip from different patients from autoimmune diseases and covet patients and so forth it's interesting how you ask the question right because if you look for similarities you're going to see similarities because they're not going to be 100 different right yeah um yeah i guess the the question is are the healthy cure cd8 cells similar in transcriptional profile to the ones that you find in disease so coming back to that question that we're saying like if there are a lot of them there is it they're just because they suck and you're recruiting more because you because they're not be able to do their job so that's why they're accumulating right because you just keep calling more in because they're not doing a good job whereas if in the healthy people are healthy because their cure cites do a great job um but i think what what i interpret from this is that definitely the the the ones from kova 19 and from ms and even some of the healthy control share a reasonable amount of signature but again it what is that level right because you can set that bar however you want to say that there are similarities or there are differences yeah they're also some unique aspects right they have a nice way of saying it they have commonality and specialness across the different conditions so and that includes the healthy controls right right they also say that um [Music] this the data they accumulate suggests that these cd8s may lose their naive or memory attributes enter the differentiation program and then suppress pathogenic cd4 cells through cytotoxicity so if they're suppressing by cytotoxicity are they cured lev expression levels low because we said that low expression was associated with cytotoxicity yeah yeah right okay uh then they looked in some in the same individuals at here plus and minus t cell receptors cd8 t cell receptors and they find that the the t cell receptor repertoire is less diverse than you would expect and this is apparently something that's been suggested before and then they they say okay what are the antigen specificities of these cure cells from different diseases and they get evidence that they may be recognizing that some of the same antigens that exist under common physiological and different pathological conditions so they say these cells the expanded key or cd8 cells have shared phenotypes and antigen specificity independent of disease type so it doesn't matter what the disease is infectious disease or autoimmune they have some shared antigen specificities which is interesting right okay now we're going to do some experiments the last set of experiments they're actually going to go back to mice and they're going to ablate ly 49 cd8 t cells and then infect the mice with virus i think this is kind of an important experiment yeah because i think it's key for for a lot of what we've talked about we've you know do they correlate do they not correlate how are we sure that they're actually acting and so here we can actually try to see if they're doing something right and nice it might right so they they are able to do this i'm not going to go through how they did it but they do they make a line of mice um which are um essentially ly49 is is not going to be functional and these mice don't have spontaneous autoimmune disorders their t-cell frequencies seem to be the same okay that's good because if they had spontaneous autoimmunity that would be a problem okay then they infect them with lymphocytic choreo meningitis virus or influenza virus so um let's see which mice did they there was when they do this with wild type mice there's a surge of ly49 cda positive t cells in the blood of wild-type mice however in their altered line of mice um the frequency of those cells remains very low all times after a viral challenge so that's interesting right they have a bladed ly49 with a single amino acid change so it must be interfering with some co-receptor interaction or something right do you know how that works i'm not sure not sure i don't know exactly how that works yeah not familiar with this model anyway those mice have have fewer 50 to 75 percent less ly 49 cd8 c cells okay and but interestingly the it's specific for the cd8s because the nks have normal levels so i i think i think these are dta yeah um yeah so yeah so i think that what happens is um the dta is a toxin that's under the a promoter an ly49 type of promoter so basically the ly49 cells make this toxin and die exactly so that's how they get different i think it's different it's like deterio toxin if it's not exactly diphtheriatoxin that's what i thought it was too yeah that's what i thought okay so it so basically they're ablating these cells because when these cells develop um they turn on um they have the promoter to turn on this specific toxin and and thus they die so is that it's the receptor well or maybe that's the toxin yeah but it doesn't matter so the effect of this alteration is that when you infect the mice you have low levels of these uh ly 49 cd8 cells right yep right now these mice have no problem clearing virus correct no problem with cd4 and cd8 responses right but they get immunopathology correct autoimmune immunopathology have uh increased numbers of follicular t cells germinal center b cells in the spleen glomerular nephritis immunoglobulin deposition in the kidney yep that's after lcmv same thing with influenza virus infected mice they get all kinds of immunopathology so that's a cool experiment it kind of so so uh cindy your original question if you take away the cells they get worse disease right so yep that's all right so if you have the cells you still get disease but it's not as bad as if you didn't have any cells right which suggests that in individuals like our severe covet patients who have high levels but still have severe disease that they're dysfunctional in some way right mm-hmm now these cells you're talking about right yeah correct like yeah correlated to the human data now they didn't have the controls here for the uninfected to see what on right yeah because they're original to study right was in the in the eae model if they took away these cells and induced eae oh no actually you started out vincent by saying if they removed these cells in the mice they got spontaneous autoimmune disease no they didn't get spontaneous right so if they remove the cells the mice are okay without any virus infection right when they're saying at the beginning when they did the dta model yeah yeah they did not appear to be they didn't show us those data okay uh supplemental figure nine it is i missed that one yeah well it's you know supplemental right easy to mix i did look through them maybe i missed it yeah they say there are no changes in the no autoimmunity no changes in uh t cells of various sorts it's just when you infect so it's quite interesting that um in the absence of these cells a virus infection will lead to auto immune responses chronic chronic so these are i mean the virus is gone it's clear the virus is clear and flu and that's that's huge i would think right so if it's the same in people then that's a big deal right right so as staff said maybe people with long covert have a problem with this subset right of something yeah sure or right and probably there's multiple cells i mean we know in case you know there's other cells doing similar things than these but we could look at just these and see you know are they defective do they does their function go down as we age which as other cells do you know yeah they show they in the cova patients they're really looking at percentages um it would be cool if they could then try to show their ability to suppress say those gliadin specific cd4s or something like that right because if you have higher percentage but then that but they suck right they can't everything that's got to be in the title now right they suck you sell suck at their job so their idea is that because we have to have all these photoreactive t-cells to deal with infectious diseases this subset of kier cd8s has arisen to take care of that as best it can but it's not always good at doing that they suck at their job right and those certain patients maybe so if the if the cd8 cures are defective if you could figure out what's defective you could then treat that right you could do gene therapy to treat it maybe yes maybe you could resolve long covid right or um yeah yeah so this that if this is true then you would have ways of treating uh long covet i guess lots more experiments still to do but sort of an interesting paradigm and it didn't i don't think that um t-regs were really figured out overnight either so it's not a criticism that there's a lot of work still too yeah it's not so they also suggest in their discussion that if and i thought this was actually a therapeutic suggestion antibody dependent blockade of 3 dl1 or 2 or l3 may further enhance the suppressive activity of cd8s towards pathogenic cd4s so these are inhibitory receptors right and they're saying if you block them with an antibody maybe you can make the cells more um able to kill let suck less right yes so maybe that would be a treatment for uh long covet right right antibodies to these kind of like monoclonal therapy right to the cell surface yeah right i think so that's what really attracted me to this this overlap of autoimmunity and infectious diseases which we know is a thing already yeah okay like the epstein-barr ms connection which we did on twit some time ago which i think is really great great illustration of that and i think what covet offers because what's really challenging to prove one it's in humans and so we're also highly variable but it's it's hard to know about viral induced autoimmunity because you don't know when people are initially infected and so it's hard to track their symptoms based on a viral infection that you may or may not know you even had and so kova does offer this opportunity to say okay we know when the virus started circulating people can pretty kind of pinpoint where when they were infected and then yes now we can go back and do time course studies to see what may be going on so tell me what is the experiment to do with long covered patients to see if there's something going on with these cure cd8s what do you do i think you could do a very similar experiment to what they did with the celiac patients you you could you could pull cells from those individuals i think the issue is with celiac what's really nice is you have a defined antigen and what's hard about lankovit is you don't have a defined antigen and then very nice reagents like tetramers to be able to probe them so you have to find what antigen if their cells are autoreactive what is the antigen there's a lot of thrombosis so maybe some i mean do you i think you start by just asking if you have elevated cdh from peripheral blood but i don't know where you know in this paper they looked at tissues that are you know have pathology in the disease i don't know where you'd look in long covert right really different from everyone right but then yeah if you want to go beyond that and get mechanistic then you don't know what the antigen is yeah maybe that's part of the study right you figure it out and maybe this brienne and vince that you know because you've interacted with lancovid researchers but are there subsets of long-covered patients that have okay this this subset of long-covered patients has they get rashes and they're they have this i don't know like very defined so that maybe you could just study that one subset or is it not really defined i am not aware of them being defined in that way um and so what i was trying to to understand i was looking back at some of the other figures um is it's not totally clear to me and i this is sort of really related to the same issues that i've just been having thinking this through sort of how exactly these cure positive cd8 t cells are specific to whatever this cell is that they are trying to to act against um and so my question is in this case they used these cells from the celiac patients and then had them act against cd4s that responded to that antigen but do you have to have that matching can you have some other situation of some kind of pathogenic t cell that's pathogenic for whatever reason um and see if the long covid um here plus cd8 would suppress right um do you have to know what the antigen is and i can't tell from these data and from this system whether what the answer is on that if you have to know or not no one of the things we didn't mention was so these these cure receptors that bind to mhc it's peptide dependent so there has to be a peptide there but it's not supposed to care what the peptide is right so it's not clear to me how that cd8 cell is going to recognize cd4 cell unless the cd4 cell is presenting a specific peptide in the context of mec class 1 that the cd8 t cell recognizes right so that would have is that an auto antigen but how but how but it's for the in case of cd4 cells the cd4 cells are specific for the glia and let's stick to the celiac model right yeah but what's in the what's in their mhc that doesn't it doesn't have what's on the class one yeah that is being recognized is that also going to be a gliadin peptide perhaps i don't know i don't know i mean you imagine that all nucleated cells are presenting self on class one all the time and and we're not supposed to respond to that right right because these guys are supposed to be recognizing that to some degree because they're somewhat autoimmune they cure cds right right but if they see that aren't they supposed to not kill especially if they have a cure because it's inhibitory right it goes back to that isn't that the whole point like if you see if you're if you look if you're seeing self peptide and mhc and you have a cure that's the combination where you're not supposed to kill well but if the t cells are recognizing it then so they the t-cells that recognize itself are not are there right they're not eliminated so right if they're there they're gonna react yeah and kill and they have to be there because the only thing that we can test against in the thymus itself that's right right there has to be another receptor you know how we talked about that there has to have many of these receptors in a cindy described depending on how you regulate so i just i'm wondering if a lot of our questions have to do with there are co-receptors that help determine this question of yeah something that the pathogenic cell expresses that is how it's recognized or something that that's how it knows here plus cell has right so is it always cd4 t cells that are the the pathogenic cells in these autoimmune diseases it can be others what other it can be cd8s what about nks i can't think of an example but in immunology my feeling is probably never i mean there are memory and k cells right so like it could be that they also play a role and and they're defined by ly49 right so but in the diseases they looked at the cd4s are involved right yeah but not cd8s or maybe and so the question really is these skier cd8 are they only regulating cd4s or can they also regulate cd8s that goes back i think to the co-receptor issue yeah i don't know because that would determine i think cell cell specificity okay yeah i you know i i discussed a little bit how the celiac disease works but sle is really an antibody-mediated disease so that will involve cd4 t cells because they're going to give help to the b cells to make antibodies but it's the antibodies and immune complexes that cause disease and in the eae model it's primarily the cd8 t cells that go in and damage the and there's actually an antibody component too i think i thought the antibodies don't cross the blood-brain barrier very efficiently there might be as there might be a component of it but i remember there was an antibody component but that's that's the end of where i remember we did i think we did learn from a couple papers ago uh that iga can make it to the brain that is true we did we did we did that paper you're right yeah so in the in the ea model it's cd8s that is that are doing the damage is that right i thought so let's see depletion of cdh and eae they don't actually mention that here they do say in celiac it's cd4 right they don't say what's doing it in eae all they say is that you can suppress it by taking out these ly4 right oh why 49 cells yeah okay all right that's uh that's uh what i thought would be cool i hope you liked it that was fun it was good discussion i learned a lot yeah yeah that's great and now i have lots of things i want to read i'd be happy not to be an immunologist i always say that about like nk cell immunologists i'm like oh gosh that level i mean how many receptors does one need well so i when i started digging because i was like i so i know cures and then i said but wait are they you know what what is the range of cures and things and i started taking notes on all of this and it's more complicated than i realized you know i i thought i knew a fair amount but apparently i don't because they're there there's like at least 13 or 14 genes and they're highly polymorphic right right yeah they're just after mhc in terms of polygons exactly and and and then they they've re they have the whole nomenclature which i looked up which is interesting and whether they have an l or an s is whether whether you can tell if they're inhibitory or stimulatory because the length of the tail and things um yeah there's there's a lot of stuff related to that and what the other thing i thought is really cool about this family of genes is it's convergent evolution between the mouse and human and the reason why they were interested and and asking this question why originally why are are there these cure c cd8 cells similar to the ly49 cd8 is because kiran ly49 although they're functionally analogous are actually completely different structurally so the lys are um in a lectin family so they have a complete different structural domain but the human ones are immunoglobulin based right so they're called different things because it's not actually the same family although they analogously do the same thing on the nk cells or now on the t cells which i also thought was really interesting yeah it really i mean for for budding immunologists for trainees there is so much still left to study so yeah study these that's immune number 55 show notes at microbe dot tv slash immune you can send us questions comments to immune at microwave.tv if you like what we do consider supporting us microbe.tv slash contribute cindy lifers at cornell university cindylifer on twitter thanks cindy thank you steph langley's at duke university stephanie langle on twitter yeah thanks this is great and brienne bark is at drew university bio prof barker on twitter thanks brianne thanks it was great to be here you are all now owned by elon musk i know wow yeah i was i was wondering do we stay did we stay with twitter or do we not stay with tonight have been approved i think that the bid has been made but he still there still has to go through a lot of legal i think there does have to be some legal stuff yesterday said okay they you know said it would be okay so it has to go forward we'll see you know cureworld hunger by twitter that's right these are hard choices 44 billion dollars hey uh elon microbe dot tv slash contribute i'm vincent rachaeniello you can find me at virology.ws the music on immune is by steve neal thanks for listening to immune the podcast that's infectious we'll be back next month [Music] you

Channel: Vincent Racaniello

Views: 3,813

Keywords: immune, immunology, regulatory T cells, COVID-189, autoimmunity

Id: MEofxdZaLUY

Length: 71min 9sec (4269 seconds)

Published: Mon May 02 2022