Sex differences in the prolongation of allogeneic skin graft survival in rats treated with cyclosporin A: effects of orchiectomy and pregnancy.

As reported previously, only male rats were susceptible to immunosuppression by CsA in allogeneic skin grafts. We have further investigated the sex differences observed in the prolongation of skin allograft survival time, focusing on the role of sex-related organs. Adult male DA (RT1a) rats (14 weeks old), which had been preorchiectomized at 5 weeks old or just 2 days prior to the operation, had fully allogeneic skin grafts from male AO (RT1u) rats, followed by CsA treatment. A small but significant reduction of graft survival time was observed in the recipients orchiectomized when fully mature. On the other hand, adult rats preorchiectomized while immature (five weeks old), showed a graft survival time similar to that of the comparable sham-operated group. DA female rats with syngeneic or allogeneic pregnancies always rejected AO skin, even in the course of CsA treatment, without showing any differences in graft survival time compared with nonpregnant rats.