antigen presentation, biological assemblage of antigen molecules (peptides) presented to T cells on the surface of cells. Exogenous antigens are taken up by macrophages and dendritic cells, digested in the lysosome, and the peptides are displayed within the class II major histocompatibility complex on the cell surface. Endogenous antigen peptides can be presented by any cell and are presented by a type I major histocompatibility complex. See also antigen processing.
