Antigen processing: a critical factor in rational vaccine design.

T lymphocytes play a critical role in host immunity, autoimmunity, and tissue rejection. There has been tremendous progress in understanding the molecular basis of T-cell recognition of foreign and self antigens. It is now well established that the major histocompatibility complex (MHC)-restricted nature of T-cell recognition is due to the interaction of the T-cell antigen receptor with MHC class I or II molecules bearing short peptides derived from antigenic proteins. In this report, we review recent progress in understanding antigen processing, ie, the mechanism by which antigenic peptides are generated in antigen-presenting cells and delivered to the appropriate MHC molecule in the appropriate intracellular compartment.