Stage-specific expression of activation antigens on NK cells at uterine implantation sites in mice.

The differentiation of the cellular components of the uterine decidua, in particular the life history of NK cells, is poorly understood. With the use of two mAbs that recognize stage-specific activation Ags on NK cells, we investigated the development of NK cells known as granulated metrial gland (GMG) cells. Immunohistochemical analysis demonstrated that mAb 3C2, but not mAb 4H12, recognized numerous cells throughout the uterine decidua basalis during early gestation. Isolated (panned) 3C2+ decidual cells from day 7 of pregnancy co-expressed the NK1.1 Ag, displayed NK cytolytic activity, and proliferated in IL-2-containing media. A small percentage of those cells expressed the GMG-associated Ag 4H12. Immunohistochemical analysis of serial sections at midgestation demonstrated that most of the 3C2+ NK cells co-expressed 4H12 Ag. During the later part of pregnancy, however, 3C2 expression in the decidua was down-regulated, and the cells expressed high levels of 4H12 Ag. When 3C2+ NK cells were isolated from cell suspensions of decidua from 7-day pregnant mice, and cultured in IL-2-containing medium, the cells developed the large and granular morphology characteristics of GMG cells, and acquired 4H12 Ag. These results demonstrate that 4H12+ GMG cells differentiate from 3C2+, NK1.1+, cytolytic precursors that reside in the decidua during early gestation.