ARG1 and neoplasm: These include Tregs that inhibit CD8+ T cells and NK cells via IL-10 and TGF-β (66, 67); MDSCs that suppress T-cell proliferation and promote angiogenesis through arginase-1, nitric oxide, and VEGF; and M2-polarized tumor-associated macrophages (TAMs) that secrete IL-10, CCL22, and growth factors supporting tumor survival (68).