Progesterone as an immunomodulatory molecule

Increased progesterone sensitivity of pregnancy lymphocytes is due to activ ation-induced appearance of progesterone binding sites in the lymphocytes. Following recognition of fetally derived antigens; gamma/delta TCR+ cells d evelop progesterone receptors. Progesterone binding results in the synthesi s of a mediator protein named the progesterone-induced blocking factor (PIB F). PIBF by acting on the phospholipase A2 enzyme interferes with arachidon ic acid metabolism, induces a Th2 biased immune response, and by controllin g NK activity exerts an anti-abortive effect. (C) 2001 Elsevier Science B.V . All rights reserved.