A corpus luteum is not a prerequisite for the expression of progesterone induced blocking factor by T-lymphocytes a week after implantation.

PURPOSE: To determine if production of the immunomodulatory protein, progesterone induced blocking factor (PIBF), requires merely progesterone or whether other factors made by the corpus luteum are required.

METHODS

The percentage of peripheral lymphocytes expressing PIBF was determined by obtaining a blood sample from women 9-12 days after embryo transfer. The embryos were either fresh ones following hyperstimulation and oocyte retrieval or were frozen-thawed embryos. Preparation for frozen embryo transfer required corpus luteum suppression with exogenous estrogen. The percentage of lymphocytes expressing PIBF was determined by an immunocytochemistry method.

RESULTS

PIBF expression (>1%) was found in 20.5% of COH and 13.3% of frozen embryo transfer cycles. There either was a significant difference or a trend for higher pregnancy rates when PIBF expression was detected.

CONCLUSIONS

These data corroborate previous conclusions that PIBF is detected in a minority of women in the late luteal phase. A corpus luteum is not required for its expression.