Fig. 4.

Pictorial representation of suppressive activity of tumor-infiltrating Tregs: Tregs secrete immunosuppressive cytokines such as TGFβ, IL10 that transforms effector T cells into anergic T cells. Immunosuppressive CD39 and CD73 molecule makes the TME favorable for tumor progression. On the other hand, Tregs absorb most of the IL2 present in the TME by acting as IL2 sink, making IL2 less available to other effector T cells leading to their apoptosis. Tregs release apoptosis inducing molecules like FasL, granzyme, perforin. Development of immunosuppressive Treg-Th17 cell is also beneficial for tumor growth. Tregs stimulate metastasis and angiogenesis by several mechanisms. Checkpoint molecules like PD1, CTLA4, LAG3, ICOS production by Treg is also a sign for uncontrolled tumor progression. Tregs convert M1 macrophages (anti-tumorigenic) into M2 macrophages (pro-tumorigenic) which work with Treg to promote tumor growth (Created in BioRender.com).