Brief Communication: In Vivo and In Vitro Tests of Inhibitory Effect of Progesterone on Cell-Mediated Immunity in Rats Bearing a Syngeneic Uterine Adenocarcinoma

Summary

Growth inhibition or stimulation of target adenocarcinoma cells in rats sensitized with spleen cells from syngeneic tumor-bearing rats was significantly suppressed in colony inhibition assays when the spleen cells were treated in vitro with 0.8 µg progesterone or morel ml medium. In addition, when tumor-bearing rats were treated with 1 mg medroxyprogesterone acetate weekly in vivo, the inhibiting action of the spleen cells from rats with regressed tumors was also suppressed. Progesterone thus suppressed immune spleen cells in vivo and in vitro.