The crucial anti-inflammatory function of IL-10 is well illustrated by the early discovery that spontaneous Th1-driven colitis occurs in global IL-10 knockout (Il10−/−) mice.90,91 However, IL-10 can regulate diverse immune responses during infection, autoimmunity, allergy, and cancer, as reviewed elsewhere.92 Here, we focus on IL-10 regulation of immunity during infection and allergic inflammation in the lung. This evidence concerns the gene IL10 and cancer.