PROGESTERONE-INDUCED BLOCKING FACTOR SEEN IN PREGNANCY LYMPHOCYTES SOON AFTER IMPLANTATION

PROBLEM: The immunomodulatory effect of progesterone (P) in pregnancy manifested via a protein named the P-induced blocking factor (PIBF) wa s previously reported. The goal of this study was to measure and compa re the PIBF expression on lymphocytes between pregnant and non-pregnan t women especially in early pregnancy. METHODS: PIBF expression was de termined by immunocytochemistry using a PIBF-specific polyclonal antib ody. Levels were assessed during the mid-cycle, luteal phase, and firs t trimester of pregnancy. RESULTS: PIPE expression was found in 24.9% of mid-cycle sera, 49% of luteal phase sera of women who failed to con ceive, and 75% of luteal phase sera of women who conceived. CONCLUSION S: These data indicate that the percentage of PIBF expressing lymphocy tes increases as a result of pregnancy and that the stimulus for PIBF induction occurs soon after implantation. These data support the conce pt that PIBF may play an important role in early implantation possibly by inhibiting the destructive function of natural killer lymphocytes.