Modulation of human T cell functions by surface sulphydryl groups: differential effects on IL‐2 production and responsiveness
An impermeable thiol blocker has been used to investigate the role of sulphydryl (SH) groups in the production of and responsiveness to IL‐2 by normal human T lymphocytes. Surface SH blockade of mononuclear cells prior to incubation with mitogen (phytohaemagglutinin, concanavalin A, CD3 MoAb) had no effect on production of IL‐2 but markedly impaired cellular responsiveness to exogenous IL‐2. Studies using MoAbs indicated that this effect was accompanied by decreased expression of both the CD25 and p75 subunits of the IL‐2 receptor. Blocking surface SH groups did not affect binding of IL‐2 to p75 on unstimulated mononuclcar cells, but inhibited binding to high‐affinity receptors on a T lymphoma cell line. The data are consistent with the hypothesis that sulphydryl groups on the IL‐2 receptor are required for its function and may be involved in the interaction of the CD25 and p75 subunits leading to generation of the high‐affinity binding site. The surface thiol identified on the IL‐2 receptor may be a candidate for oxidation on cells from patients with chronic inflammatory diseases such as rheumatoid arthritis and thus contribute to the aberrant function of T cells in these patients.