Administration of DTC gives evidence of a role of the thymus in the control and regulation of factors inducing thymocyte differentiation in the mouse.

Nude (B6) mice, grafted with a syngeneic thymus, are treated 3 wk later with 25 mg/kg of sodium diethyldithiocarbamate (DTC). Serum sampled 24 h afterwards is heated at 56 degrees C for 45 min and tested over a large range of doses for its in vitro capacity to induce Thy-1+ cells in nu/nu spleen cells. Data are compared with the effects of DTC on ungrafted nude mice, and on B6 and C3 mice. Each group comprised 5 to 6 animals. The thymus of B6 mouse abrogates the action of DTC to induce in thymus-less mice two serum factors, active at different concentrations. The serum of DTC-treated C3 mice has an increased T-cell recruiting activity in contrast with the serum of DTC-treated B6 mice. The findings are interpreted as evidencing the extra-thymic origin of one active factor, and a role for the thymus to regulate the synthesis of both factors.