Multiphasic modulation of signal transduction into T lymphocytes by monoiodoacetic acid as a sulfhydryl reagent

Actions of monoiodoacetic acid (MIA) as a sulfhydryl reagent on the different stages of the T cell receptor (TCR)–mediated signal transduction were examined. MIA (1 mM) prevented anti‐TCR (CD3) monoclonal antibody (mAb)–induced energy‐dependent receptor capping but at the same time promoted the anti‐CD3 mAb/mitogen‐induced tyrosine phosphorylation of the T cell activation‐linked cellular proteins of 120, 80, 70, 56, and 40 KDa. Relatively low concentration (0.01 mM) of MIA further promoted anti‐CD3 mAb‐induced transcription of c‐fos, production of IL‐2, and cell surface expression of IL‐2 receptors. The MIA‐promoted TCR‐mediated IL‐2 production actually required signal transduction that could be inhibited by cyclosporin A, genistein, or H‐7. In contrast, the same concentration of MIA as promoted the signal transduction for cell activation severely inhibited the anti‐CD3 mAb‐triggered signal delivery for cell proliferation, selectively at its early stage. We conclude from these results that MIA differentially affects various steps of signaling into T lymphocytes, suggesting that there exist multiple sites of MIA‐sensitive or redox‐linked control in the signal cascade. © 1995 Wiley‐Liss, Inc.