Fig. 2.

Cell interactions in the tumor microenvironment involve various immune cells. CD8⁺T cells release IFN-γ and tumor necrosis factor α (TNF-α), which leads to the inhibition of tumor cell growth. Similarly, CD4⁺T cells release IFN-γ, interleukin-2 (IL-2), and TNF-α, contributing to the inhibition of tumor cell growth. NK cells release IFN-γ and TNF-α, resulting in the inhibition of tumor cell growth. Tregs release transforming growth factor-β (TGF-β) and IL-10, leading to the inhibition of CD8⁺T cell function. Furthermore, MDSCs release TGF-β, prostaglandin E2 (PGE2), and ARG1, which inhibits CD8⁺T cell function, while Bregs release TGF-β and IL-10, also leading to the inhibition of CD8⁺T cell function. Different polarizations of macrophages in the tumor microenvironment play a significant role in influencing tumors. M1-type macrophages can activate CD8⁺T cells through antigen presentation or secretion of IFN-γ and TNF-α, thereby exerting anti-tumor effects. Additionally, M1-type macrophages can directly kill tumor cells. On the other hand, M2-type macrophages inhibit CD8⁺T cell function by secreting IL-10, TGF-β, and IDO, contributing to the suppression of the immune response. This diagram was drawn by Figdraw (www.figdraw.com)