PEPTIDE TRANSPORTERS AND ANTIGEN PRESENTATION

Presentation of endogenously derived nonapeptides to the T cell receptor of CD8+ T cells is the central event of the cell mediated immune response. Peptides generated from proteolysis of intracellular proteins must cross the endoplasmic reticulum lipid bilayer in order to associate with major histocompatibility complex class I heavy and light chains. This translocation is dependent on the presence of a putative peptide transporter heterodimer. This paper reviews the recent discovery, inside the major histocompatibility complex class II region, of genes encoding this transporter and two of a cytoplasmic proteolytic system called the proteasome.