THE THYMUS ATROPHY INDUCING ORGANOTIN COMPOUND DBTC STIMULATES TCR-ALPHA-BETA-CD3 SIGNALING IN IMMATURE RAT THYMOCYTES

In the present study, we show that the thymus atrophy inducing compoun d DBTC stimulates the intracellular release, but not the influx, of Ca 2+ elicited by cross-linking of the TcR alpha beta-CD3-complex on rat thymocytes and inhibits capping of TcR alpha beta. Similarities with t he effects of cytochalasin B together with the finding that DBTC also inhibited capping of CD8, whereas cross-linking of CD8 did nest cause a Ca2+-response, suggest that DBTC interferes with TcR alpha beta-CD3- signalling by selective interference with cytoskeletal functioning. Th e responding thymocytes were CD53- and FSClow, thus possibly including the non proliferating counterpart of the presumed immature CD4-CD8(+) CD53- target cells of DBTC. The present effects may therefore relate t o the mechanisms of organotin-induced thymus atrophy. (C) 1995 Academi c Press, Inc.