Evidence that the Expression of Progesterone‐Induced Blocking Factor by Maternal T‐Lymphocytes Is Positively Correlated with Conception

PROBLEM: To compare the expression by T‐lymphocytes of an immunomodulatory protein known as progesterone‐induced blocking factor (PIBF) in conception versus non‐conception cycles even when there has been definite fertilization and embryo formation. METHOD: PIBF expression on T lymphocytes was measured using an immunohistochemical method with a PIBF‐specific polyclonal antibody. These levels were determined in patients undergoing three types of therapy: non‐in vitro fertilization (IVF), IVF‐embryo transfer (ET), and frozen ET. Sera were drawn 12 days from ovulation in non‐IVF cycles or 9 days after ET and were assayed for PIBF and beta human chorionic gonadotropin. Comparison of the frequency of lymphocyte expression of PIBF in pregnant versus non‐pregnant women were made. RESULTS: PIBF was detected in 29.5% of non‐pregnant women and 52.5% of pregnant women. There were no differences in PIBF levels by therapy used in non‐pregnant cases or in the pregnant group. CONCLUSION: These data are consistent with the hypothesis that maternal expression of PIBF in T‐lymphocytes soon after trophoblast invasion may depend on successful implantation.