TNF and deltaretrovirus infections: The effects of these antibodies are less understood for infectious diseases, but anti-PD-L1 antibodies have been shown to enhance T-cell response in vitro, such as cell proliferation and the production of interferon-γ (IFN-γ), interleukin-2 (IL-2), tumor necrosis factor-α (TNF-α) and Granzyme B, during HIV, HBV, and HTLV infection [12–15].