How do the Major histocompatibility complex class I and II molecules differ in function?
They differ in their cellular distribution, the antigenic peptide fragments they present, and the type of T cell that recognizes and responds to the complex they present.
Function of Major Histocompatibility Complex Class I and II Molecules
|MHC Class I||MHC Class II|
|Cellular distribution||All nucleated cells and platelets||Antigen-presenting cells:• B cells• Monocytes/macrophages• Dendritic cells• Thymic epithelial cellsSome activated T cells|
Some cells in which MHC Class II is induced, particularly during chronic inflammation:• Endothelial cells• Synovial cells
|Antigen size||8–13 amino acids in length||13–25 amino acids in length|
|Antigen type||Antigen peptides found inside the cell (self-peptides, intracellular pathogens, or tumor antigens)||Phagocytosed or receptor-mediated endocytosed antigen taken into the lysosome (extracellular pathogens)|
|T-cell recognition||CD8+ T cells||CD4+ T cells|
|T-cell response||Cell-mediated cytotoxicity of the cell presenting the antigen on MHC class I||T cell coordinated phagocytic and/or antibody response to eradicate the presented antigen|