• Platelet rosette formation;
  • leukocyte adhesion factor

PROBLEM: To determine if the embryo may induce adhesive molecules needed for implantation.

METHOD: Determination of whether platelet rosetting around lymphocytes might occur when exposed to sera from pregnant, but not nonpregnant patients and from culture fluid from embryos but not oocytes.

RESULTS: 90.2% of women with positive sera beta human chorionic gonadotropin (P-hCG) levels taken at least 12 days postovulation demonstrated platelet rosette factor (PRF) vs only 18.7% when β-hCG was negative. Using mid-luteal phase sera in women receiving hCG injection 1 wk before, 64.7% had positive PRF when serial β-hCG levels were positive as did 100% of samples taken from in vitro fertilization (IVF) patients; however, only 15.3% were positive with negative serial hCG levels. Culture media from fertilized oocytes and embryos tested positive for PRF, but follicular fluid and media from unfertilized oocytes were negative.

CONCLUSION: The early embryo secretes a factor(s) that gains access to maternal serum and promotes increased lymphocyte/platelet adhesiveness.