THE INVOLVEMENT OF INTERLEUKIN (IL)-15 IN REGULATING THE DIFFERENTIATION OF GRANULATED METRIAL GLAND-CELLS IN MOUSE PREGNANT UTERUS

Previous studies have suggested that granulated metrial gland (GMG) ce lls are bone marrow-derived lymphoid cells, which differentiate in sit u in the mouse pregnant uterus into natural killer (NK)-like cells. Si milar to NK cells, GMG cells express an abundant level of cytolytic me diators such as perforin. The factor(s) regulating the differentiation of GMG cells remain(s) to be identified, although cytokines previousl y implicated in the stimulation/activation of NK cells (e.g., IL-2, IL -6, IL-7, and IL-12) can be considered as potential candidates. Recent ly, IL-15, a novel cytokine, which displays biological activities simi lar to IL-2, has also been shown to be capable of activating NK cells. Using reverse transcription-polymerase chain reaction (RT-PCR) analys is, we have demonstrated in the present study that IL-15 and its cogna te receptor, but not the other cytokines, are expressed in the mouse p regnant uterus, with a time course concomitant with those of cytolytic mediators in differentiated GMG cells. Moreover, IL-15, though not IL -2, is capable of inducing the expression of perforin and granzymes in pregnant uterine tissues explanted in vitro. Data obtained from in si tu hybridization study have suggested that the macrophages present in the pregnant uterus may be responsible for the production of IL-15. Th ese results suggest that IL-15 is involved in regulating the different iation of GMG cells during mouse pregnancy.