Suppression of thymocyte proliferation in vitro by a dioctyltin dichloride-induced serum factor.

Oral administration of dioctyltin dichloride (DOTC) results in the production or release of factors which appear to prevent thymocyte maturation at an early stage. Sera obtained from rats gavaged with 75 mg DOTC/kg on alternate days, significantly inhibited PHA-induced blastogenesis of normal thymocytes. In vitro uptake of tritiated thymidine by thymocytes obtained from DOTC-gavaged rats was markedly reduced. These events occurred 24 to 72 h after commencement of DOTC treatment and preceded overt thymic weight loss. The effects of DOTC may therefore be a consequence of factor(s) capable of blocking the intrathymic differentiation of T cell precursors.