Thus, the addition of IL-2 mimicking a paracrine signal promotes effector differentiation in vitro as it has been demonstrated in vivo.4,5,10 This function of IL-2 is not restricted to naive cells as in a chronic infection or tumor context, IL-2 signaling combined with anti-PD1 immunotherapy drove the differentiation of exhausted stem-like progenitors CD8 T cells toward a population with increased effector functions and enhanced antiviral and antitumor responses,32,33 thereby highlighting the therapeutic potential of IL-2 in the treatment of cancer and chronic infections. The gene discussed is IL2; the disease is neoplasm.