Long-Term Low-Dose IL-2 Enhances Immune Function in Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) is a primary immunodeficiency disease characterized by hypogammaglobulinemia and lack of antibody production. Numerous T cell defects have been described, including reduced gene expression and production of IL-2. Since some of the T cell defects could be explained by lack of IL-2, we have been investigating the effects of in vivo IL-2 treatment. Here, a long-acting form of IL-2, PEG-IL-2, was given for 12–18 months to 15 randomly chosen CVID subjects, in comparison to 39 CVID subjects who served as controls. After 6 to 12 months of treatment, T cell proliferative responses to mitogens and to IL-2 were significantly enhanced; proliferative responses to tetanus and candida antigens increased up to 50-fold. Four of eight subjects immunized with the neoantigen bacteriophage φX 174 displayed increased antibody responses after treatment. Treated subjects recorded reduced, but not overall statistically significant, days of bronchitis, diarrhea, and joint pain. These data indicate that IL-2 might serve as an adjuvant to therapy in some subjects with CVID, enhancing T cell functions and reversing T cell anergy in most.