Three decades of T-ology

Tremendous progress has been achieved in our understanding of thymus function in the last 3 decades. Distinct T cell subsets have been characterized and shown to have an essential role in initiating and in regulating a variety of immune responses. The ontogenetic events which lead to their intrathymic differentiation have been mapped and have allowed studies on the selection of the T cell repertoire. The major histocompatibility complex and associated antigenic peptides play a major role in T cell selection and antigen activation. The T cell receptor for antigen and the genes which code for it have recently been identified. Future studies should allow some insight into how to activate specific T cells more effectively for vaccination purposes and how to switch them off to induce tolerance to transplanted tissues.