In contrast, M2-type microglia are activated by anti-inflammatory cytokines, such as IL-4, IL-10, IL-13, and TGF-β, and secrete anti-inflammatory and immunosuppressive factors such as CCL5, TGF-β and MMPs, which facilitate tumor cell proliferation and the establishment of brain metastases. The gene discussed is TGFB1; the disease is neoplasm.