Innate CD8aa+ cells and osteopontin promote ILC1-like intraepithelial lymphocyte homeostasis and intestinal inflammation

Innate CD8+ cells, also referred to as iCD8 cells, are TCR-negative intraepithelial lymphocytes (IEL) possessing cytokine and chemokine profiles and functions related to innate immune cells. iCD8 cells constitute an important source of osteopontin in the intestinal epithelium. Osteopontin is a pleiotropic cytokine with diverse roles in bone and tissue remodeling, but also has relevant functions in the homeostasis of immune cells. In this report, we present evidence for the role of iCD8 cells and osteopontin in the homeostasis of TCR-negative NKp46+NK1.1+ IEL (ILC1-like). We show that in the absence of iCD8 cells, the number of NKp46+NK1.1+ IEL is significantly reduced. These ILC1-like cells are involved in intestinal pathogenesis in the anti-CD40 mouse model of intestinal inflammation. Reduced iCD8 cell numbers and/or osteopontin expression results in a milder form of intestinal inflammation in this disease model. Collectively, our results suggest that iCD8 cells and osteopontin promote survival of NKp46+NK1.1+ IEL, which significantly impacts the development of intestinal inflammation.