Suppression of immune responses by progesterone.

Biodegradable sustained release progesterone-collagen dosage from prolonged significantly the survival of hamster-rat and mico-mice skin grafts. The duration of immune response suppression could be correlated to progesterone concentration in the collagen matrix. Collagaen sponges, sponges containing pregnenolone, estradiol, or cortisol were not effective in prolonging skin graft survival.