IL-33 acts directly on various immune and non-immune cells as a vital alarmin and proinflammatory factor, playing important immune regulatory roles and diverse biological functions that include: (1) mediating type 2 immune response, as IL-33 can stimulate mast cells, neutrophils, ILC2s, naive T cells, and other immune cells to secrete the type 2 cytokines IL4, IL-5, and IL-13, among others; (2) enhancing Treg cell immunosuppressive function; (3) promoting ILC2s to produce AREG for tissue repair; (4) directly promoting tumor growth. This evidence concerns the gene IL5 and neoplasm.