Hypersensitivity Immune Responses

welcome to this lecture on hypersensitive immune responses these are a set of conditions where essentially your immune system over reacts to a particular stimulus and this can lead to significant inflammation cellular damage and possibly leaving to even death so as you can see on the board we've got a table now the types of hypersensitive disorders are broken into four types 1 2 3 4 so sometimes these are called type 1 2 3 4 now what we'll go through today is firstly the antigen so this is the stimulating factor that causes the response to begin with we look at what part of your immune system is the main player to cause this reaction we look at a basic mechanisms for each type give a couple of disease examples that you should know for each type and then finally we have a really good mnemonic which gives you a better way to memorize or remember these particular types so let's start with type 1 this one is also known sometimes as IG II mediated and thought so what that means is I GE in this case is an antibody antibodies are these proteins that are produced by b-cells and there are a number of different types in this in this case it's a type II type now what happens in this case is we've got an antigen and the antigen in type 1 is freely moving so it comes from the outside world into your body so it's freely floating around so we'll just call it free ly moving now some examples of the antigen that we could think about is like pollen or we could think be venom or maybe a protein in peanuts now the immune component as we said is an antibody called I G a so that's pretty easy to remember and so far now the mechanism the big player is the Marcel with IgM so what has to happen is the pollen or we use pollen as an example but that is the antigen comes into the body okay so the pollen comes in let's say you sniff it in okay it will get picked up by a b-cell okay the B cell will essentially react to it and then what it will do is it will release a whole lot of antibodies and so the first exposure this is what we call the priming or the sensitization is causing all these IgE antibodies which is related to the particular antigen in this case it's the pollen and these will start to be released now in this particular case they they will stick to the mast cell so the marcel's now have this particular antibody IgE antibody attached to it okay so that's got it all over now these marcel's can sit in strategic locations like in your skin in your mucous membrane in your Airways or sometimes in blood vessels so now they're primed now they're sensitized now the second exposure comes in so now the pollen comes back and the pollen in this case will bind to these antibodies and the Marcelle so if that's in your respiratory tract the Marcelle will then just spew out release all of its internal contents in this case histamine which will spread everywhere in that location this is going to cause inflammation so it's going to cause vasodilation and it's going to cause increased permeability so that area will become swollen and think about if you have hay fever it's going to cause your eyes to run your nose or your eyes to become watery and those to run Airways become harder to breathe and so this is essentially a type 1 reaction now some examples of diseases these are all centered around something called a tepee which is a type of kind of allergic response and this couldn't be allergic asthma okay or even anaphylaxis and and so that's a really exaggerated response and so what could happen there is in your blood vessels they all become really dilated or your blood volume or your blood pressure will drop quite significantly your airway will close in and this can actually lead to death if it's not rectified and so this is essentially a type-1 reaction it's all centered around IgA IgE the marcelles okay and because we've got a lot of a's here at the asthma allergies anaphylaxis we're gonna them mnemonic is going to be a ok so that's type 1 type 2 this this type is called cytotoxic okay so you could probably guess by that name the cell would die in this case now when you compare it to type 1 where we had a freely moving antigen in this case the antigen is fixed so it is fixed on the cell whereas the immune component in type 1 was IgE and that was that was the the fixed part but in this type it's freely moving so the antibody is freely moving now it's not a type a e in this case it's a type i GG or IG and and so there the antibodies using this case now an example so when we look at our red blood cells we have types of socially with it and so if you are a type A that means you have antigens on your red blood cells that are a type and that would mean that you have antibodies against the B so if you were given a B type of blood you would have antibodies against it with toward react to it and so if you think about it let's assume that your are type a so this is a type A blood type so I'll put a there okay so the antigen okay if you're a Type A is here type I ain't like so that means you've got you've got antibodies so these are the these Y shaped things that would be against B so that would be in your blood normally now if you gave it a person that the type A blood and you gave them Type B so there's now a mismatch these B antibodies would lock on to it okay so that would bind to it like so like that and that would cause a complement response and so the other part of the immune component is complement now once you have this reaction it's going to cause a lead to death of that particular complex so this cell would be killed off so if you were a type A blood and you were given a type B blood this reaction would occur and all those type B blood cells would get killed off and they would not exist anymore and that reaction would be quite significant and the patient would present with certain inflammatory responses this could be also in the newborn so with the Reese factor in compatibility so if the mothers got a type of Reese which is different to the baby this could be a reaction now which could cause a hemolytic anemia in them new bond another example so I should rather the transfusion incompatibility now another type is what we call good pasture syndrome so good pasture good syndrome now what happens here the cell in this case is in your kidney and it's got an antigen on it which is essentially going to be I think a type of collagen and that collagen is the antigen the antibody which is either a JJ or IgM reacts to that causes a complement response which then kills off those particular cells in your glomerulus and that causes a type of nephritis which is problematic in this case now in terms of the mnemonic and because we got cited toxic it's a cytotoxic response and because we use complement or use the letter C okay so that's the second moving on to the third type this is an immune complex wrist complex type or response so basically what is going to happen here is the antigen is now freely moving freely moving so it's moving around the body the antibody is freely moving freely moving okay and so it together it forms an immune complex now where could where could the antigen come from so an example could be from a bacteria so if you have a bacterial infection such as streptococcus this particular infection could be killed off by you your immune system but the a certain antigen from it can be moving through your bloodstream which will meet up with an antibody and in most commonly in type 3 is also another IgG and these together meet up so what we can see is there's your antigen say let's from the bacteria it meets up and gets bound to with the antibody these wise and together now this group is a complex and now it's moving through your blood and so once it's moving it's not so much an issue but if it binds to a certain tissue so if it goes into your kidney or get stuck into your blood vessel there's certain cells around there like in your blood vessels like a basil fill or in your kidneys like a neutrophil can release certain cytotoxic or cytokines which can cause inflammation in that area so you this complex could go to your kidneys and could lead to a type of glomerulonephritis or it could go into your blood vessels and cause a kind of vasculitis and so some examples would be host strep glomerular nephritis variety or SLE which is a type of lupus and so in this in this case the antigen is like a DNA DNA or RNA you're in body reacts to it causes a complex and that can go into certain parts of the body like in the in the blood vessels and called that vasculitis now because this particular one is an immune complex okay immune complex driven and we're going to call it an AI okay now finally we move to type for example although another name for this is delayed okay so this is a delayed type the antigen is generally going to be movable so it's really moving and so it's similar to type one it can come into the body now in terms of the immune component here there's no antibodies driven in this type this is more a lymphocyte okay so particularly at T helper cell okay that's the big player in this so if you are exposed to a certain antigen okay let's say like latex so let's say you get this from gloves and that antigen comes into the body this will be taken up by a macrophage so the macrophage will swallow it up okay then what it will do is it will present it on the front of its membrane and then along comes the T helper cell T helper and it will kind of bind to it in that presentation and this will cause the t p-- helper cell to become sensitized so it's very similar to what we saw over here with the sensitization but in this case this was through a b-cell and IgE this is through a T helper cell so this is a lymphocyte reaction and then this will potentially just duplicate itself and you'll have a whole lot of T helper cells that are primed to that particular antigen in that case it's latex so when that comes back in the T helper cell can react quite quickly so this latex binds to the T helper cells which then will release cytokines and that those cytokines will bring more macrophages in so now macrophages come to that area where you have the exposure and in this case it's going to be in your hands because that's where your little using your latex gloves and those macrophages will release chemicals that will then cause dermatitis okay and this will take 48 to 72 hours so it's delayed unlike this one which is immediate very quickly both of them will need sensitize in but this reaction beacon is when you have your secondary exposure like pollen or peanuts or bee venom very quick this one's going to take 48 to 72 hours to respond so it's delayed ok so that's how that's different this one doesn't use antibodies this one uses lymphocytes okay now some examples is dermatitis as I said so that can be contact dermatitis such as latex another example is diabetes okay so type 1 diabetes and in this case it would be your beta cells in your pancreas which would have that reaction and kill them off leading to type 1 diabetes and because we're using dermatitis diabetes and delayed we're going to have D which gives us the mnemonic acid and so hopefully when you think acid now you can remember the four types of hypersensitivity we've got the type 1 the type 2 type 3 type 4 hopefully you can give an example of them mechanisms and how they're different how the antigen and immune complex reacts slightly different and a few examples for each and if you find hard to remember always go back to the mnemonic acid

Channel: Dr Matt & Dr Mike

Views: 17,411

Rating: 4.951952 out of 5

Keywords: NCLEX, USMLE, Hypersensitivity, Type 1, Type 2, Type 1 Hypersensitivity, Type 2 Hypersensitivity, Type 3 Hypersensitivity, Type 4 Hypersensitivity, Immune System, Immune disorders, Allergy, Anaphalaxis

Id: xWCIgE1HKfA

Length: 15min 1sec (901 seconds)

Published: Thu Feb 21 2019