Inhibition of lymphocyte responses by gold: modulation by time of drug addition and antigen dose.

Gold sodium thiomalate added to peripheral blood mononuclear (PBM) cell cultures inhibits the mixed leukocyte reaction (MLR), and cell-mediated cytotoxicity (CMC). The addition of GST to MLR was inhibitory only if the compound was added at the beginning of culture; late addition of GST did not inhibit MLR, or CMC. In a different set of experiments the number of stimulating cells added to MLR was varied. The inhibitory effects of GST decreased markedly as the number of stimulating cells added to culture was increased. The effects of gold in vivo may be modulated by a number of immunologically competent cells that are already antigenically stimulated, as well as by the amount of available stimulating antigen.