Fig. 4. Immune evasion strategies of tumors.
Malignant cells and their supporting stroma 1) secrete immunosuppressive cytokines such as transforming growth factor-β (TGFβ) or interleukin-10 (IL-10); 2) attract immunosuppressive cells such Tregs or MSDCs; 3) inhibit dendritic cell maturation; 4) express molecules on the cell surface that suppress immune cells including FAS-L and PD-L1, and; 5) create a metabolic environment (e.g. high lactate, low tryptophan) that is immunosuppressive.