Regulatory T-Cell Responses to Low-Dose Interleukin-2 in HCV-Induced Vasculitis

This phase 1–phase 2a study of the use of low-dose interleukin-2 to treat vasculitis associated with HCV infection suggests the presence of a therapeutic effect that is mediated by an increase in regulatory T cells. Interleukin-2 has been identified for its capacity to stimulate T cells in vitro 1 and has been used to boost effector immune responses in patients with cancers and infectious diseases. 2 , 3 It is a registered indication when used as an adjunct for the treatment of renal-cell carcinoma, but there is a response to treatment in less than 10% of those with the disease, a finding partly explained by the discovery that interleukin-2 mediates the survival and suppressive function of regulatory T cells (Tregs), 4 which are known to suppress antitumor effector responses. 5 , 6 A marked increase in levels of Tregs has been . . .