Effects of D-penicillamine on mononuclear cells in vitro.

D-penicillamine (D-pen) inhibited pokeweed mitogen-induced plaque-forming cell (PFC) response in a dose-dependent manner. This inhibition was irreversible as preincubation for a few hours with the drug followed by washes still caused suppression of the PFC response. Pretreatment of the different mononuclear cell populations with D-pen for short periods (2-24 h) showed that both macrophages (Mo) and B lymphocytes were affected by the drug. By contrast T cells were resistant. Mo appears to be more susceptible to D-pen than B cells, and in the case of drug-treated Mo, the response was restored completely with the addition of 20% fresh Mo. Our results show that D-pen, without exogenous Cu2+, inhibits the polyclonal immunoglobulin secretion by human mononuclear cells in vitro due to a strong effect on both Mo and B cells. This may explain the decrease in serum immunoglobulin levels seen in patients with rheumatoid arthritis undergoing this therapy.