ANTIGEN PRESENTATION AND THE MAJOR HISTOCOMPATIBILITY COMPLEX ANTIGENS

Most animal cells (except mammalian erythrocytes) express molecules on their surfaces which are strongly recognized as non-self by other, genetically non-identical, individuals. These major histocompatibility antigens show considerable similarity in structure to the immunoglobulins and T-cell receptor proteins. They play an important (though not exclusive) role in transplant rejection and some transfusion reactions. They are also fundamentally involved in the “presentation” of processed antigens to T-lymphocytes, which is especially important in the development of immune responses. Antigen-presenting cells such as macrophages, dendritic cells, and B-lymphocytes process antigens by degradation (which is mediated by enzymes) and present the resulting peptides, bound in grooves on the major histocompatibility complex (MHC) molecules, to responding T-cells (see Histocompatibility Groups). The type of the MHC molecules and their ability to present antigen influences significantly the strength and nature of the resulting immune response.