CD56+ cells are recruited to the uterus in two waves: at ovulation and during the first 2 weeks after missed menses.

PROBLEM: Uterine natural killer (uNK) cells are enriched in the post-ovulatory uterus and during pregnancy. Whether these cells arise from blood pre-cursors or from stem cells in the uterus is undefined. To support a hypothesis that precursors of uNK cells are recruited from blood, adhesive function of blood CD56+ subsets were assessed during one cycle and during pregnancy.

METHOD OF STUDY: Fifteen women of proven fertility provided serial blood samples during one menstrual cycle and thirty women with a history of implantation failure or recurrent spontaneous abortion provided serial samples during infertility treatment.

RESULTS: CD56(bright) cells, but not CD56(dim) cells or NKT cells, increased in ligand-binding capacity during ovulation in fertile cycles only and during the first 2 weeks from date of missed menses.

CONCLUSION: Enhanced adhesive function at ovulation in CD56(bright) cells in fertile cycles and during early gestation supports a hypothesis of recruitment of pre-uNK cells from the blood CD56(bright) subset.