Immunocytochemical characterization of the unusual large granular lymphocytes in human endometrium throughout the menstrual cycle

Leukocyte populations were studied at all stages of the menstrual cycle using a panel of monoclonal antibodies to natural killer cells, T cells, B cells, and macrophages on frozen sections of endometrium. At the time of implantation (mid-secretory phase) the majority of leukocytes appear to be Leu19+, CD16-, Leu7-, CD2+, CD3-, CD5-, CD7-, and HLA DR- with the morphology of large granular lymphocytes. The numbers of these cells showed a marked increase in the mid-secretory phase. These cells exhibited similar phenotypic characteristics to those found in decidua. These findings, therefore, suggest that the recruitment of these large granular lymphocytes to the uterus is under hormonal control and is not a local response to the presence of invading trophoblast.