CLONAL DELETION AS DIRECT CONSEQUENCE OF AN INVIVO T-CELL RESPONSE TOBACTERIAL SUPERANTIGEN

To date clonal deletion of peripheral mature T cells is restricted to in vivo model systems characterized by prolonged exposure of mice to a ntigens and clonal T cell expansion preceding clonal deletion. Here we describe that upon challenge of mice with the superantigen staphyloco ccal enterotoxin B two immediate events become imposed on ligand-react ive Vbeta8+ T cells in lymph node cells draining the local site of inj ection. First, and within hours Vbeta selective clonal deletion is ini tiated via an apoptotic process. Second, the remaining Vbeta8+ T cells first develop a profound state of ligand-specific unresponsiveness an d subsequently initiate clonal in vivo growth. It is suggested that th e dichotomy of events observed reflects a direct consequence of T cell receptor occupancy in the context of inappropriate signalling.