Control of lymphocyte homeostasis by iCD8a cells and osteopontin

总结

SUMMARY In this application we propose to investigate the biological features of innate CD8 cells (or iCD8 cells), a novel lymphoid population present in the intestinal epithelium discovered by our group. A hallmark of this population is the expression of CD8, lack of T and B cell receptors, and the production of cytokines/chemokines that indicate an innate immune phenotype. iCD8 cells are a main source of osteoponin in the intestinal epithelium, a cytokine known for its role in tissue remodeling but also for its capacity to stimulate Th1 and Th17 immune responses. Interestingly, using a strain of mice lacking iCD8 cells (E8I mice; E8I is an essential enhancer for CD8 expression in IEL) we found that the levels of -/- osteopontin in the intestinal epithelium are decreased in comparison to wild type mice, and that E8I-/- mice have a deficiency in NKp46+NK1.1+ IEL. These and other preliminary results have led to the hypothesis that iCD8 cells, through production of factors such as osteopontin, promote the survival and maintenance of IEL. In order to pursue this hypothesis, we propose the following complementary, yet independent aims: Aim1. To determine the contribution of iCD8 cells and osteopontin to IEL maintenance and survival. In this aim we will determine: a) the impact of iCD8 cells and osteopontin in the survival and proliferation of different IEL subsets; b) the impact of iCD8 cells and osteopontin in the immune environment of the intestines; and c) the role of osteopontin ligands in IEL homeostasis. Aim 2. To define the role of iCD8 cells and osteopontin during intestinal inflammation. In this section we will determine the role of iCD8 cells and osteopontin in three different disease models: a) intestinal inflammation by anti-CD40 antibody treatment, b) Citrobacter rodentium infection, and c) inflammation caused by adoptive transfer of effector T cells into immunodeficient mice. Aim 3. To determine the mechanisms controlling IEL homeostasis by iCD8 cells. Our previous publication indicates that IL-12 provides stimulus for activation of iCD8 cells. In this section we will determine a) the impact of IL-12 in activation of iCD8 cells, with implications on OPN secretion and IEL survival, and b) we will determine the gene expression signature of IEL responding to iCD8 cell/OPN stimulation.