The main effects of IL-2 are Induction of activated T - and B-cell proliferation Enhancement of NK-cell cytotoxicity and killing of tumor cells and bacteria by monocytes and macrophages Clinical relevance of IL-2 includes For IL-2, treatment of metastatic renal cell carcinoma and metastatic melanoma For anti-IL-2 receptor mAb, help with prevention of acute kidney rejection IL-3 is produced by T cells, NK cells and mast cells The main effects of IL-3 are Stimulation of growth and differentiation of hematopoietic precursors Stimulation of mast cell growth Clinical relevance of IL-3 includes Targeting of IL-3 receptor alpha chain with monoclonal antibodies or CAR T cells, which may be of benefit in patients with relapsed refractory acute myeloid leukemia IL-4 is produced by mast cells, NK cells, natural killer T (NKT) cells, gamma-delta T cells, Tc2 cells, and Th2 cells.