Major Histocompatibility Complex (MHC) - Human Leukocytic Antigen (HLA) - Immune System

what's going on everybody it's mithicosas perfect schneiderless where medicine makes perfect sense today we'll talk about the major histocompatibility complex also known as the human leukocytic antigens as you know we have two types of mhc mhc-1 and guess what mhc2 these freaking scientists are super creative it's mind blowing mhc is very important because it can be involved in many diseases now let's get started today we'll discuss the general idea behind mhc if you want the technical stuff check out my rheumatology playlist i had several videos about the doofuses example hlab27 is associated with enclosing spondylitis which affects my vertebral column my spine and my sacroiliac joints among others hladr2 is associated with lupus and other diseases the basic idea is simple the mhc is the tray that the waiter used to present the food to the customer oh wait wait wait a minute coasters tell me about this again who's the waiter antigen presenting cells like who macrophage b lymphocytes dendritic cells okay and what's the food the antigen a piece of the bacteria all right how do you present the food on a tray who's the tray mhc major histo compatibility complex here's your food sir on a tray wanna be a tracer i'm a ready tracer and who the flip is the customer the lymphocyte the customer has many options the customer will eat the food the customer will remember the food memory cells and the customer can become plasma cells which secrete antibodies the redundant one present on all nucleated cells and the kind of unique one only for the antigen presenting cells because usually the lymphocyte that is eating the food from the antigen presenting cell is cd4 positive and i will teach you soon that when this is cd4 it's going to interact with mhc class 2 so that 4 times 2 equals 8. how about cd8 ocd8 lymphocytes will interact with mhc class 1 so that the product equals 8 as well this is the story of immunology bacteria invade your body take a piece of it the piece is called the antigen the antigen presenting cell is going to take that piece and present presented to the lymphocyte the food is presented on a tray the tray is the major histocompatibility complex since this lymphocyte is probably cd4 the mhc is mhc2 the mechanics of what happened between antigen presenting cells and t lymphocytes were discussed in detail before in a nutshell here is the antigen presenting cell it took a piece of the bacteria called the antigen it's gonna process it and cook it and present it to the t lymphocyte let's establish that this is cd4 therefore it's interacting with mhc class 2 that's the tray so let's play this game please bring a piece of paper and draw four empty circles in the first circle if i told you that this is cd8 positive t lymphocyte oh it's eight therefore it has to interact with mhc class one so that the product eight times one has to equal eight thank you so much captain obvious but what if we're talking about the other cell which is cd4 positive well four has to interact with mhc class two so that 4 times 2 also equal 8. this is probably the oldest mnemonic in medical history and there you go here's a t lymphocyte here's a t lymphocyte but this is cd4 positive it interacts with mhc2 this is cd8 positive it interacts with mhc1 please remember the functions cd4 positive oh this was the helper i help my sister i help my neighbors who's your sister the cd8 t cytotoxic cells who is your neighbor the b lymphocyte i'm gonna help my sister kill the virus infected cells the cancer cells the fungi etc and i'm going to help my neighbor the b lymphocyte become active secrete plasma cells to fight those bacteria major histocompatibility complex why call it major because they're another group that's called minor okay that's like the main one yep complex why do you call it complex because it's made of many proteins oh it's not just a simple thing no it's not just an element in the freaking periodic table we're talking about a complex here and look at this word histocompatibility it has to be compatible with your own tissue so hey melecosis are you trying to say that my major histocompatibility complex is different than that of a monkey which is different from that of a freaking cockroach absolutely right it has to be histo compatible since many organisms have mhc we have to recognize and specify the human virgin with a unique name and this is the human leukocytic antigen or hla so h of a are mhc in humans tada that's it we have mhc class 1 found in all nucleated cell that was the redundant tray and then we have the kind of special tray this is restricted to the mononuclear cells such as lymphocytes macrophages etc class 1 mhc interacts with cd8 t lymphocytes aka the cytotoxic t cells but class 2 will interact with cd4 t lymphocytes the helper cells pause and digest now let's take it a step further class 1 mhc is divided into three hlas in humans h l a a b and c very creative nomenclature what comes after abcmd thank you you're so cute hlad belongs to the class 2 mhc and then we subdivide hlad into do you remember your ekg yeah p wave q wave r wave oh dp dq dr why do you have to start with p it's latin doofus primum secundum etc or it could be greek from proto or whatever who cares we have dp dq dr the dr is further subdivided into dr2 dr3 dr4 pause and review rest and digest just like your parasympathetic nervous system let's draw this from scratch we're talking about what mhc in humans human likositic antigen why because these proteins are antigens and they are in humans which part of humans plays leukocytes white but cells of human beings oh the antigen presenting cells in them yeah those are the white blood cells those are the do faces then they are subdivided into mhc class 1 mhc class 2 and mhc class 3 which no one cares about mhc class 1 is going to interact with cd8 t lymphocytes the cytotoxic how about mhc2 is going to interact with cd4 t lymphocytes the helpers that was cool tell me more about mhc class one it includes hla a l a b h l a c tell me about class 2 mhc it includes h l a d and d will be subdivided into dp dq dr and the dr is going to be further subdivided into dr2 dr3 dr4 love it pause and review and please draw it from your scratch on your own with your hands on paper otherwise i guarantee you'll forget it on your exam but wait there's more hla a is not just one doofus it's 22 different types of proteins how about dr 18 i just gave you three but they're actually 18.

my goodness gracious homolyticosis are these clinically relevant abso freaking lootly example hla3 is associated with a disease known as hemochromatosis hlab well that's a long story hla b8 graves disease addison's disease myasthenia gravis the cruel auto antibodies destroyed and ate my thyroid eight my adrenals and eight my energy and volition hlab27 is the famous seronegative spondyloarthritis including the famous pear and i don't care what's the p psoriatic arthritis what's the a and closing spondylites what's the eye inflammatory bowel disease related arthritis like crohn's ulcerative colitis with arthritis etc and odd is the reactive arthritis formerly known as writer syndrome next we have hla b47 congenital adrenal hyperplasia and hlab 51 is beschette syndrome since we're talking about human leukocytic antigens or major histocompatibility complex which is a complex made of proteins and proteins are coded by genes you will find some genetic variation mhc class 2 associations in rheumatology are numerous example dr2 lupus multiple sclerosis autoimmune hepatitis good pastor syndrome narcolepsy and much more all of this was discussed in my rheumatology playlist and i added even more diseases here please pause and review normally each type of your hla human leukocytic antigens is in a separate locus or separate genetic locus on your freaking chromosome which is part of your dna of course what is mhc polymorphism then it's the extensive range of hla antigens here's the first antigen second engine third third antigen all of them are on chromosome and of course i can have wide range or narrow range of genetic loci and the range of antigens on these loci in other words different people are different when it comes to passing down your genes each person has two copies of each hla antigen one from mommy one from pups ergo you can be homozygous or heterozygous mhc is not just involved in some rheumatological conditions it's also related to organ transplant rejection you know if i did not match the new kidney with your body you can actually attack the kidney and the matching does not just include blood grouping like you are blood group a positive and the donor is a positive therefore your match that's not about it we have much more we have to also match your mhc because it has to be histocompatible otherwise you will destroy the new kidney or the new kidney will destroy you aka graft versus host disease suppose that i your doctor am a doofus and i forgot to match the mhc you know what's gonna happen you can reject your kidney how did the graft get rejected here's the new kidney it's antigenic to your body it has proteins that are foreign to your body these proteins are recognized by your antigen presenting cells which present the antigen to the lymphocytes and don't forget what was the name of the tray mhc if this is cd4 we're talking about mhc class 2. cd4 is the helper it's going to help her sister and help her neighbor help her sister destroy the new kidney cy too toxic toxic to the tissue and help the neighbor become plasma cells to secrete antibodies to destroy the new kidney so whether you go the hemorral route or that cell mediated route you're screwed either way that's why you better match the mhc before you give me an organ pause and review if you like this video you will enjoy my antibiotics course it has 40 videos about antibacterials antivirals antifungals and anti-parasitic medications downloaded today at medicosisperfectionness. com no subscription needed you download it once and keep it for you forever even if you lose the files after 10 years just send me an email i'll send you new links to download this is just who he is i also have a renal physiology course at medicosisperfectionalis.