Immunity 9, White blood cells

so blood as you probably know contains blood cells and plasma so we have blood and it contains plasma and the plasma is the fluid component of the blood all the other cells float in the plasma and plasma is largely water but it contains proteins hormones nutrients waste products things that are circulating around the body in the plasma but as well as plasma the blood contains cells blood cells so there's plasma and there's cells and there's two types of cells there's the red blood cells and the white blood cells so first of all the red the red cells are the arthro sites arthro actually means red and these are well-known cells in anatomy and physiology they're B concave discs they have an area of central Pala which is a third or less of the diameter of the whole cell and looked at from the side we can see why they have an area of central P it's because they're B concave discs and these red cells are transporting the oxygen around the body but what we're particularly interested in the context of the immune system are the white blood cells so there's red cells and there's white cells and the white cells are correctly termed the lucos sites now some people do spell it with a K but the English traditional English spelling is with the c lucos sites the white blood cells and if there's an increase in the number of white blood cells in the blood that's called a if someone has a Luc coyos when you look at their blood cells there's a test called a differential white cell count where we can count the number of lucaites if that's increased if there's a lucco yosis then that's an indicator most commonly of infection because the white blood cells are essential to fight infection so when there's infection in the body the body cleverly increases the number of lucaites it gives the body a increased number of white cells to see off and kill off this infection conversely if there wasn't enough white blood cells that that can be quite a serious condition that's called a lucenia and that can give rise to immuno deficiency people are prone to overwhelming infections if they have a deficiency of these essential white blood cells so the white cells are the lucaites and basically there's two classifications of the white cells of the lucaites and the first one we're going to think about are the granulocytes the Granulos sites and these are soall because they have a granular looking cytoplasm under light microscopy and there's actually three types of granular sites we're going to consider the first is BAS oills the second is neutrophils and the third is eosinophils so these are the three types of granular sites so we've said the white cells are the lucaites one type of lucite is the granulites and there's three types of granular cyes basophils neutrophils and eosinophils now the basophils the cell has a loed nucleus joined together and basophils have very large granules in their cytoplasm actually now we know that they're not really granules we now know that they're vesicles containing various chemicals now there's very few basophils actually present in the blood but basophils migrate into the tissues where we call them MK cells and the mass cells are very important in the local inflammatory response so bzo fills with very large vle or granules then we can think about eosinophils now the eosinophils also have a lobe nucleus and again it's joined together and the EO cils have mediumsized granules in their cytoplasm and again we know these aren't granules we now know they're vesicles containing various chemicals important in immune defense the eosinophils and the eosinophils if there's an increase in the number of eosinophils that's called an eosinophilia an increase in the number of eosinophils eosinophilia and that can happen in allergic reactions it can happen when there's chronic inflammation and it also happens do you know when else you get a neophilia allergic reactions chronic inflammation what's the other classic condition where you get eosinophils and increase in eosinophils well it's where you have parasitic parasitic infections so if you're working in tropical countries and you're getting multicellular parasitic organisms causing infection an eosinophilia can be The Telltale sign of that so basophils eosinophils then neutrophils now neutrophils are by far in the way the most abundant form of granular sites in the blood and the neutrophils have a load nucleus of several loes it can be three loes sometimes it's four loes that gives rise to the other name of polymorph sorry polymor polymorphonuclear sites polymorph nuclear sites polymorphonuclear sites and these have relatively small granules in their cytoplasm and again we know they're not granules we know that they are vesicles and if there's an increased number of neutrophils that's called a neutr filia an increased number of neutrophils in the blood and you get a neutrophilia particularly with bacterial infections because the neutrophils will migrate to areas where there's bacterial infection they'll start phagocytosing the bacteria so the body needs to produce more so if there's an area of infection that can be detected by some of the cells in that area particularly the macres the macro fages will produce cytokines which are chemical Messengers these cytokines will go off to the bone marrow in the bone marrow there are reserves of neutrophils the polymorphonuclear cell cells and these will come into the blood you'll get an increased number of neutrophils in the blood there'll be a neutrophilia but the really clever thing is the neutrophils might great to where the infection is and you'll find them in the tissues where there's areas of infection where they'll deal with that bacterial infection so neutrophilia if there's too many neutrophils neutropenia if there's not enough neutrophils neutropenia and sometimes there's a great reduction a very significant reduction in the number of neutrophils and that's often referred to as an a granular cytosis and a granular cytosis what that would literally mean is no granular cells because these are of course granular sites and if there's a very significant reduction and a granular cytosis that patient's life is at risk from overwhelming bacterial infection because that's what the nutrifil do they counter B cial infection so granular sites basophils neutrophils eosinophils the next classification of cells are the a granular sites the a granul sites now these are cells which don't have apparent granules in in their cytoplasm in light microscopy in actual fact some of them do but this is how they were discovered that when the people first looked at them they said they had no granules in their cytoplasm with more Advanced Techniques we can see some granules actually so the a granular sites so what sort of cells are we talking about here well first of all we can mention the Tho sites what's the other name for thrombocytes you remember the thrombocytes the thrombocytes are the platelets vital for the process of blood plotting they're really cell fragments that are present in the blood but they're absolutely vital for blood plotting other a granular sites are monocytes monocytes and monocytes are the absolutely the vital white blood cell I suppose they're all vital really but the monocytes are particularly important because the monos sites can migrate into the tissues so the monocytes can migrate into the tissues and in the tissues the monocytes will become what we call macr fages Big eaters macr fages so monocytes can become macro fages the monocytes actually the blood have a typically a sort of a horseshoe shaped nucleus really kidney shaped more like a kidney bean shaped nucleus it's that kind of shape but when the monocytes migrate into the tissues they change their name to macrofagos so in the blood they're called monocytes in the tissues they're called macres and if there's any bacteria or dead cells in the tissues to eat the these monocytes which are now macres will eat lots and lots of this necrotic material they they'll eat lots and lots of bacteria and antigenic material in the process of Phagocytosis and they become can become really big cells macro vages big eaters and monocytes can also give rise to another type of cell called dendritic cells well I'm saying that monocytes can give rise to dendritic cells that's almost certainly true almost certainly true and the dendritic cells are dendrites do you know what dendrites are it's like branch-like processes isn't it dendrites so the dendritic cells have like branch light processes like this coming off the central part here and what these do is they collect antigens and they present the antigens to the lymphocytes so they're sometimes called antigen presenting cells apcs so these dendritic cells are present in areas like the skin if they come across an antigen they will take that antigen in then the dendritic cells will migrate to the lymph nodes in the lymph nodes the dendritic cells the antigen presenting cells will present this antigen to the lymp ites and the lymphocytes will then mount a specific immune response so really these dendritic cells are sometimes described as the link between innate immunity and specific immunity innate can pick up a very wide variety of antigens in the skin or wherever they are in the mucous membranes but then they go off to the lymph nodes communicate with the lymphocytes which mount a highly specific immune response to the particular antigen so a granulites thrombocytes monocytes which can become macres or dendritic cells what's the other big classification of a granular sites in the blood and also found in the lymphatic tissue of course it's the lymphocytes too many lymphocytes would be a lymphocytosis an increase in the number of lymphocytes in the blood and this typically occurs if there's a viral infection so if you find that someone's got a lymphocytosis when you look at the differential white cell count it probably means they've got a viral infection but of course it's good that you get a lymphocytosis because it's the lym lyes that combat the viral infections as well as other things but they largely Prime combat the viral infections now lymphocytes can be divided into two types they can be big what you think the other ones might be so there's the big lymphocytes or the small lymphocytes now the big lymphocytes are cells with the great name of the natural killer cells they are the nks the nks and they have a nucleus and a cytoplasm as you would expect and actually I know we're on the a granular sites but these have granules in their cytoplasm because what the enk cells do the natural killer cells is they will kill virally infected cells so if a cell has a virus in it it the natural killer cell will recognize this from viral antigenic fragments on the surface of the infected body cell and these cells don't mess about they just kill the whole cell that's bad because it kills your own cells but it's also good because all the viruses were inside and they're all killed at the same time so lymphocytes can be big which are the enks or it can be small and all the small lymphocytes have a very large nucleus compared to the size of the cytoplasm they have a large nucleus so we have small lymphocytes and the small lymphocytes are one of two types they can be B lymphocytes or they can be T lymphocytes B lymphocytes mature in the bone T lymphocytes mature in the thymus gland now the B lymphocytes when there's an infection the particular B lymphocytes and these B lymphocytes differentiate into an effector cell a cell that actually does something something useful very useful in fact and these affector cells are called plasma cells the plasma cells and the plasma cells have a smaller nucleus but they have a very large arrangement of endoplasmic reticulum and apparatus to excrete material from the cell because what the plasma cells do is they produce the immunog globul they are the factory for the antibodies so these are producing lots and lots of absolutely vital antibodies which are wide shaped molecules and these antibodies are specific to the particular antigen that the B cell line has been activated against so the B cells differentiate to plasma cells which produce the antibodies absolutely vital to fight the infection now the te- cells are slightly complicated because there's three types of t- cells there's t- helper cells T suppressor cells and there t cytotoxic t-cytotoxic cells now again the number of te- cells will increase when there's a particular infection to combat and the helper cells work because the helper cells stimulate the B cells to produce the antibodies the immune proteins so exactly as the name says the helper cells the t-per cells stimulate the B cells or help the B cells to produce antibodies and actually do you know a disease where the T helper cells are particularly affected what disease primarily kills off t- helper cells well that's HIV human immuno deficiency virus human immuno deficiency virus causes acquired imuno deficiency syndrome AIDS is primarily disease of the tea helper cells but then we don't want these immune processes to get carried away so when the particular antigen has been dealt with when that's been killed off the t- supressor cells will also stimulate the B cells and they'll tell them to stop or limit the immune response so the t- helper cells help the immune response the suppressor cells limit it and tell it when it's time to stop mounting the immune response and the t-cytotoxic cells work in much the same way as the natural killer cells but they work in a much more specific way they'll work against virally infected cells and they'll also work against some cancer cells so just to review the a granular sites the a granular sites we have thrombocytes and monoc sites the monocytes can differentiate into macro phages or dendritic cells the other typee of a granular site is the lymphocytes lymphocytes can be big or small the big lymphocytes are the nks the natural killer cells the small lymphocytes can be big which differentiate into plasma cells which are the factory for the antibodies well the small lymphocytes can be T and they can be T helpers T suppressors or T cytotoxic cells so the white cells the lucaites are absolutely vital for the processes of immunity a deficiency of any one type of white cell will lead to amuno deficiency potentially overwhelming infection and of course that can lead to death so we depend on our white cells all the time to Keep Us Alive for for

Channel: Dr. John Campbell

Views: 90,691

Keywords: White blood cells, leucocytes, immunity, monocytes, neutrophils

Id: ZmK0mfYc3aY

Length: 22min 38sec (1358 seconds)

Published: Tue May 21 2013