MHCs and antigen presentation Flashcards
MHC molecules
glycoproteins encoded in a large cluster of genes locked on chromosome 6, found on the surface of host cells
MHCs are also known as
human leukocyte antigens
principles functions of MHCs
to present antigens of pathogens to T cells to discriminate between self and nonself
how many types of MHC molecules
actually three: MHC I, MHC II, MHC III
MHC I structure
2 polypeptide chains, a larger chain encoded by chromosomes 6 in the MHC region and a smaller b2 micro globulin, encoded on chromosome 15
MHC II structure
2 polypeptide chains, a + b, both endcoded in the MHC II region on chromosome 6
MHC I binds
CD8
MHC II binds
CD4
CD8
kill
CD4
immune response
MHC I are expressed
on all nucleated cells
MHC II are expressed
only expressed on antigen presenting cells- lymphocytes, macrophages, dendritic
what regulates expression of MHCs
cytokines e.g. IFN-y increases the expression of MHC I/II and induces MHC II expression on cells that wouldn’t normally present them
what plays a huge role in T cell activation
level of MHC expression
Outline the process which occurs when a dendritic cells processes a pathogen and displays an antigen on an MHC I receptor on the outside of the cell
antigens inside a cell are bound to class I MHC molecules, and brought to the surface of the cell by the class I MHC molecule where they can be recognised by T cells. If the TCR is specific for that antigen it binds to the complex and the antigen and the T cell destroys the cell. In order for the TCR to bind to the class I MHC molecule, the formed must be accompanied by a glycoprotein called CD8. Therefore these T cells are called CD8+ T cells.
CD8 T cells are recognised as Tc cells once they have become activated and have a cytotoxic role within the immune system. Also have the ability to make some cytokines
