TNF and neoplasm: It is reported that, Natural killer cells as well as T-cells expresses cytokines such as interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α) and interleukin-2 (IL-2) which in turn can induce PD-L1 expression on surrounding immune and tumor cells when T-cells recognize antigen and become activated [27].