IL23A and skin neoplasm: Mice that had lost IL‐23 function via deficiencies in either IL‐23p19 or IL‐23R or by treatment with antibodies to IL‐23p19 showed resistance to skin tumor growth/development (Table 4).20 IL‐23–deficient mice70 and mice treated with anti–IL‐23p1971 have also been shown to have an increased resistance to melanoma‐induced lung metastases.