 Hi everyone, welcome to the basic science series by Dr. Lokendra Kumar. I have created this program to promote scientific knowledge among students and young researchers. In the previous episode, we discussed about the major histocompatibility complex in general. We also identified that there are three classes of major histocompatibility complex that is class 1, class 2 and class 3. In this presentation, we will focus on the structure and function of major histocompatibility complex class 1 molecule in detail. We will also focus on the interaction of CD8 coreceptor and the function of various domains of MHC class 1 molecule. So, please watch the full presentation to understand the structure and function of MHC class 1 molecule. The first question is where MHC class 1 molecules are found. They are present in almost all the cells of our body. They are present on the cell surface of all nucleated cells. It is very important to note down that they are present on platelets but not on the red blood cells. Let's know about the structure of MHC class 1 molecule. MHC class 1 molecules are heterodimers. That means they are consist of two polypeptide chains, alpha chain and beta 2 micro globulin chain. Alpha chain contains three domain, alpha 1, alpha 2 and alpha 3. Alpha and beta micro globulin chains are linked non-covalently via interaction of beta 2 micro globulin and the alpha 3 domain. The alpha chain is encoded by a HLA gene while the beta 2 micro globulin unit is encoded by the beta 2 micro globulin gene. MHC class 1 molecule complex interacts with CD8 coreceptor and T cell receptor to recognize foreign molecules. The alpha 1 and alpha 2 domains fold to make up a groove for peptides to bind. It is very important to note down that the alpha 3 domain interacts with the CD8 coreceptor. The alpha 3 CD8 interaction holds the MHC 1 molecule in place while the T cell receptor on the surface of cytotoxic T cells bind with the alpha 1, alpha 2 chains and checks the coupled peptide for its antigenicity. MHC class 1 molecule binds with peptides that are predominately 8 to 10 amino acid in length but the binding of longer peptides have also been reported. When a foreign protein enters in our body the antigen presenting cells generate the peptides using proteosomes. Proteosomes are protein complexes which degrade unneeded or damaged protein by proteolysis. The MHC class 1 peptide complex is then inserted via endoplasmic reticulum into the external plasma membrane of the cell. The epitope is bound on extracellular part of the class 1 MHC molecule. Thus the function of class 1 MHC is to display intracellular protein to cytotoxic T cells. A normal cell will display peptides from normal cellular protein via class 1 MHC molecule. And cytotoxic T cells will not be activated in response to them due to the central and peripheral tolerance mechanisms. When a cell expresses foreign proteins such as after viral infection a fraction of class 1 MHC will display these peptides on the cell surface. Consequently cytotoxic T cells specific for the MHC peptide complex will recognize and kill the infected cell. In the next episode I will be covering exciting topics of immune systems so please stay tuned and don't forget to subscribe the YouTube channel. With this note I conclude this presentation. I hope you understand what is MHC class 1 molecule and its role in human health. Please subscribe the channel and share the presentation with students and young researchers. Please forgive my mistakes. Thank you and Namaste.