Abstract
Recent advances in our understanding of biosynthesis and assembly of MHC subunits are discussed. Intracellular traffic of MHC proteins is reviewed in the context of antigen presentation. While the overall picture of antigen presentation is now clear, much of the detail of the early stages of assembly of MHC products remains to be established. The degradative pathways that result in the peptides presented by MHC molecules (in particular those serving Class I molecules) have not yet been identified with certainty.