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MAJOR HISTOCOMPATIBILITY COMPLEX (MHC) - Coggle Diagram
MAJOR HISTOCOMPATIBILITY COMPLEX (MHC)
MHC CLASS 2
FUNCTION
present processed antigens, which are derived primarily from exogenous sources, to CD4(+) T-lymphocytes.
initiation of the antigen-specific immune response
activates intracellular signaling pathways, frequently leading to apoptosis.
STRUCTURE
Class II molecules are composed of a polymorphic a chain noncovalently attached to a polymorphic B chain. Both chains are glycosylated; carbohydrate residues are not shown. The ribbon diagram shows the structure of the extracellular portion of the HLA-DR1 molecule with a bound peptide, resolved by x-ray crystallography.
ANTIGEN PROCESSING AND PRESENTATION
CD4+ T cells play important role in immune response against foreign protein antigens, help macrophage to destroy phagocytosed microbes and stimulate the proliferation and differentiation of B cellls.
CD*+ T cells are useful in cytotoxicity against virus infected and tumor cells and take part in regulation of immune response.
B cells can recognize antigen in free or cell bound form whereas T celss recognize antigen only they are associated with MHC protein
APC
Function of APC
antigen concentration
antigen collection
antigen processing
antigen presentation
conversion of phagocytosed native protein to MHC-associated peptide fragments by APCs is called antigen processing
monocytes-macrophages, dendritic cells, B lymphocytes are considered professional antigen presenting cell (APC)
APCs not only present antigens to T lymphocytes, they are also the targets of T cell effector functions.
MHC CLASS 1
STRUCTURE
Consist of a large glycoprotein chain with 3 extracellular domains and a transmembrane segment, and 2 microglobulin which are consists of a polymorphic alpa chain non-covanently attached to the non-polymorphic beta microglobulin, a protein with a single domain.
FUNCTION
Peptides presented with Class 1 proteins are recognised by specific CD8+ T lymphocytes
Present peptide fragments in the cytosol (endogeneous antigen, which could be fragments of viral or tumour proteins) to the CD8+ lymphocytes.
Glycoproteins expressed on all nucleated cells
Present processed antigens to cytotoxic T cells
