Further investigation found that Treg cells express an IL-2 receptor trimer (CD25, CD122, CD132), indicating that Tregs tend to have a higher affinity for IL-2 (50, 51).In contrast, cytotoxic T cells and NK cells express IL-2 receptor dimers with only moderate affinity (52).In other words, low doses of IL-2 tend to induce Treg cell maturation to suppress immunity (53, 54), and only high doses can cause CD8+T cells and NK cells to mature and kill tumor cells (55–58). This evidence concerns the gene CD8A and neoplasm.