T-cell ontogeny: the role of a stimulator - suppressor cell

The thymus presents two major problems in cellular differentiation. How is self-non-self discrimination achieved in developing thymocytes? What determines the development of T-cell classes? In this discussion, Alan Herbert and James Watson propose a mechanism for regulating T-cell differentiation which involves the alternative pathway of T-cell activation. They postulate that T cells with a stimulator-suppressor phenotype stimulate resting helper T cells (Th) to produce interleukin 2 (IL-2) and suppress T cells which have bound antigen through antigen-specific receptors by preventing induction of IL-2 receptors. Stimulator-suppressor T cells therefore suppress the clonal expansion of T cells in an antigen-specific manner, yet promote their own clonal expansion in a manner independent of antigen. They further suggest that the molecule responsible for suppression is the product of the γ genes known to rearrange in γ cells.