Interleukin-2-regulatory T cell axis critically regulates maintenance of hematopoietic stem cells

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-? 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-? activity could do the same even in the absence of T(reg) cells. Our study suggests that equilibrium in IL-2 and IFN-? activity is critical for steady state hematopoiesis, and in clinical conditions of BM failure, IL-2 or anti-IFN-? treatment might help to restore hematopoiesis.