A delicate balance: Tweaking IL-2 immunotherapy

The cytokine interleukin-2 (IL-2) is important for the activation of several types of immune cells, including T cells, and its clinical potential has been previously explored in the context of boosting immune responses to cancer and infectious diseases. However, two recent studies provide evidence that low-dose IL-2 therapy can suppress adverse immune reactions. Koreth et al.¹ showed that IL-2 therapy reversed graft-versus-host disease (GVHD) in patients who had undergone allogeneic hematopoietic stem cell transplantation (HSCT) to treat lymphoma or leukemia. Similarly, Saadoun et al.² found that IL-2 treatment had clinical benefit in hepatitis C virus (HCV)-related vasculitis with IL-2. Both studies suggested that IL-2's therapeutic effects might be mediated through suppressive regulatory T cells (T_reg cells), as T_reg cell counts were higher in treated individuals. We asked three experts to comment on the implications of these studies for IL-2 immunotherapy.