Inhibition of Human Helper T Cell Function In Vitro by d-Penicillamine and CuSO₄

The effect of d-penicillamine (Pen) and mixtures of Pen and copper sulfate on the capacity of normal human peripheral blood mononuclear cells (PBM) to generate immunoglobulin-secreting cells (ISC) in response to the T-cell-dependent polyclonal B-cell activators pokeweed mitogen (PWM) and staphylococcal protein A (SPA) was examined. PBM obtained from normal individuals were incubated for 1-2 h at 37°C with medium alone, Pen, CuSO₄, or a mixture of Pen and CuSO₄. After washing, the cells were incubated for 6-7 d with PWM or SPA and then, with a reverse hemolytic plaque assay, assayed for the number of ISC generated. Preincubation of PBM with either Pen (100 μg/ml) or CuSO₄ (2 μg/ml) did not alter the subsequent capacity of the cells to generate ISC in response to PWM or SPA. In contrast, responsiveness to both mitogens was nearly abolished when PBM were similarly preincubated with a mixture of Pen and CuSO₄. Inhibition of responsiveness could not be ascribed to cell death, carry-over of the inhibitors, or an alteration in the concentration of PWM or the length of incubation yielding maximum responses. Co-culture experiments demonstrated that Pen and CuSO₄ preincubation had not caused augmented suppressor cell function. Experiments in which PBM were separated into adherent and nonadherent populations indicated that Pen and CuSO₄ preincubation inhibited the responsiveness of the nonadherent cells but did not alter the accessory cell function of monocytes. To determine whether Pen and CuSO₄ preincubation effected T- or B-cell function, PBM were separated into B- and T-cell-enriched populations, individually preincubated with Pen and CuSO₄, and then co-cultured with PWM. The results indicated that Pen and CuSO₄ markedly inhibited helper T-cell function and had little effect on the capacity of B cells to generate ISC. The observation that in the presence of CuSO₄ Pen inhibits helper T-cell activity may, in part, explain the therapeutic efficacy of Pen in rheumatoid arthritis and especially the capacity of Pen therapy to decrease antiglobulin titers in treated patients.

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