Defective monocyte accessory function due to surface sulphydryl (SH) oxidation in rheumatoid arthritis

Low serum sulphydryl (SH) levels are a feature of active rheumatoid arthritis (RA). We have investigated whether a similar blockade of membrane SH groups on mononuclear cells modifies the function of these cells in this disease. Using pokeweed mitogen stimulated IgG synthesis as the assay system, we have found that the accessory cell function of peripheral blood monocytes is totally dependent on free SH groups on the cell surface. Monocytes from patients with active RA display poor accessory cell function when compared with healthy monocytes or with cells from patients treated with D-penicillamine. The poor function of the rheumatoid accessory cells may be corrected in vitro by 2-mercaptoethanol (2-ME). Addition of 2-ME to the culture system also enhances IgG synthesis by rheumatoid mononuclear cells to normal levels. We suggest that surface SH-dependent mechanisms are responsible, at least in part, for the depressed mononuclear cell functions of rheumatoid cells in vitro and may explain some effects of D-penicillamine therapy in rheumatoid patients.