Fraction of the peripheral blood concentration of CD56+/CD16-/CD3- cells in total natural killer cells as an indication of fertility and infertility.

Objective: To determine whether the peripheral blood concentration of CD56(+)/CD16(-)/CD3(-) cells, the main natural killer (NK) subpopulation that colonizes the endometrium in the middle and late secretory phase, can be related to fertility or infertility status.

Design: A case control study.

Setting: Immunopathology department of an infertility laboratory.