CD1-ENTEROTOXIN-B( HUMAN THYMOCYTES PROLIFERATE IN RESPONSE TO SUPERANTIGEN STAPHYLOCOCCAL)

Exposure of human thymocytes to superantigens results in the deletion of thymocytes expressing specific TCR-V beta genes. The factors that c ontribute to this deletion may relate to the inherent nature of the T cell at a given stage of development. In this paper, we demonstrate th at CD1(+) human cortical thymocytes are capable of proliferating in re sponse to a bacterial superantigen (staphylococcal enterotoxin B (SEB) ) in the presence of autologous CD2(-/low) thymic APCs. Phenotypic ana lysis of the responding populations revealed that the majority of the CD1(+) cells were CD4(+)CD8(low) or CD8(+)CD4(low) cells. The response is triggered by low concentrations of SEB, requires the participation of the TCR and IL-2R molecules, and is inhibited by cyclosporin A. Th ymocytes that express specific V beta genes are expanded, which result s in an engagement profile that parallels that found in PBLs. Addition ally, four V beta-chains that have not been reported previously are sh own to engage SEB. Once stimulated, the thymocytes failed to respond t o additional SEB; however, they could be induced to proliferate with I L-2, which suggests that these expanded populations had become anergic . These data represent the first demonstration of a human cortical thy mocyte subpopulation that responds to superantigen by proliferation an d subsequent anergy.