Inhibition of T lymphocyte activation by estramustine: dose-dependent interference with IL-2 production and later...

Estramustine, a nitrogen mustard derivative of estradiol-17 beta widely used for treatment of prostatic cancer, was found to inhibit the proliferative response of mouse lymphocytes to T (concanavalin A) and B (lipopolysaccharide) cell mitogens in vitro. Concanavalin A-induced lymphoproliferation was considerably more sensitive to the antiproliferative effect of estramustine than lipopolysaccharide-stimulated proliferation. The concentration of estramustine selectively inhibiting T lymphocyte proliferation was only active when present during the first 24 h of culture and could be overcome by exogenously added interleukin 2. Estramustine was shown to directly inhibit the production of interleukin 2 in concanavalin A-stimulated lymphocyte cultures without affecting the expression of interleukin 2 receptors. Thus the preferential inhibitory effect of estramustine on mitogen-induced T lymphocyte activation is apparently mediated by interference with the production or release of interleukin 2.