Lymphocyte-derived progesterone-induced blocking factor corrects resorption in a murine abortion system

An anti-abortive effect of a progesterone-induced blocking factor has been shown in the CBA/J x DBA/2 abortion system. I.p. injections of pregnant mice on days 7.5, 9.5, and 11.5 of gestation with dialyzed supernatants from progesterone-treated murine pregnancy spleen cells (but not from control ones) significantly (P less than 0.01) reduced the resorption rate from 47.7% in the untreated animals to 20.7%.