Modern concepts in immune recognition and lymphocyte activation. Relevance for the development of useful vaccines.

Adaptive immunity requires both specific recognition of an antigen and its translation into appropriate lymphocyte responses. This paper reviews the striking differences in B- and T-lymphocyte antigen recognition, details the pathways for conversion of protein antigens into peptide-major histocompatibility complex molecule ligands for T-cell receptors, and summarizes the roles of costimulatory signals in lymphocyte activation. This information is used to suggest new approaches for the rational design of vaccines.