Sabrina Giampaolo, Gabriela Wójcik, Edgar Serfling, Amiya K. Patra

• The role of IL-2 in HSC maintenance is unknown. Here we show that Il2\(^{−/-}\) mice develop severe anomalies in HSC maintenance leading to defective hematopoiesis. Whereas, lack of IL-2 signaling was detrimental for lympho- and erythropoiesis, myelopoiesis was enhanced in Il2\(^{−/-}\) mice. Investigation of the underlying mechanisms of dysregulated hematopoiesis in Il2\(^{−/-}\) mice shows that the IL-2-T\(_{reg}\) cell axis is indispensable for HSC maintenance and normal hematopoiesis. Lack of T\(_{reg}\) activity resulted in increased IFN-γThe role of IL-2 in HSC maintenance is unknown. Here we show that Il2\(^{−/-}\) mice develop severe anomalies in HSC maintenance leading to defective hematopoiesis. Whereas, lack of IL-2 signaling was detrimental for lympho- and erythropoiesis, myelopoiesis was enhanced in Il2\(^{−/-}\) mice. Investigation of the underlying mechanisms of dysregulated hematopoiesis in Il2\(^{−/-}\) mice shows that the IL-2-T\(_{reg}\) cell axis is indispensable for HSC maintenance and normal hematopoiesis. Lack of T\(_{reg}\) activity resulted in increased IFN-γ production by activated T cells and an expansion of the HSCs in the bone marrow (BM). Though, restoring T\(_{reg}\) population successfully rescued HSC maintenance in Il2\(^{-/-}\) mice, preventing IFN-γ activity could do the same even in the absence of T\(_{reg}\) cells. Our study suggests that equilibrium in IL-2 and IFN-γ activity is critical for steady state hematopoiesis, and in clinical conditions of BM failure, IL-2 or anti-IFN-γ treatment might help to restore hematopoiesis.…