Abstract
Innate lymphoid cells (ILCs) are emerging as important effector cells in innate immunity and tissue homeostasis. Group 2 ILCs (ILC2s) have been identified in organs and tissues, such as adipose tissue, small intestine, lungs and skin, where they are involved in helminth immunity, type 2 immune responses, and tissue pathology and recovery. Using flow cytometry, we identified ILC2s in mouse uteri and confirmed IL-5, but not IL-13, production in response to IL-33 both in vivo and in vitro. Furthermore, intraperitoneal administration of IL-33 induced recruitment of activated ILC2s to uteri as well as to lungs. To investigate the possibility that uterine ILC2s might play a role in maintaining a healthy pregnancy, we mated ST2-/- females (on a Balb/c background) with ST2-/-, MHC-matched Balb/c and MHC-mismatched C57B6 males (ST2 is the IL-33 receptor). Balb/c, C57B6 and Balb/c x C57B6 pairs were used as controls. Litter sizes were not significantly different among the pairings. We defined viable pups as those still alive 24 hours after parturition. Total numbers of non-viable pups, percent of litters with at least one non-viable pup and percent of non-viable pups per litter were significantly increased in ST2-/- x C57B6 pairs when compared to control pairs. Thus, IL-33-responsive ILC2s are present in murine uterine tissue and may play roles in successful reproduction.
