PD-L1 and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), arginase 1 (ARG1), high-mobility group box 1 protein (HMGB1), and TGF-β are among the proteins found in tumor cell exosomes related to immunosuppression [30,96,97,98,99]. The gene discussed is ARG1; the disease is neoplasm.