Antigen recognition by T lymphocytes.

Many questions remain about the mechanisms of antigen recognition by T cells. Is antigen processing an absolute requirement for recognition by helper T cells? Does processing affect those areas of the antigen which associate with class II major histocompatibility complex (MHC) molecules (la antigens) or those which associate with T cell receptors or both? Where in the antigen-presenting cell (APC) does processing occur, and where does processed antigen associate with la? These questions were posed and discussed at a recent meeting on the immunology of proteins and peptides.