CTLA4 and neoplasm: Tregs use several mechanisms to suppress immune responses, such as the production of inhibitory cytokines, e.g., TGF-β, IL-10 or IL-35 [86,87,88,89], or the transition of APC from a tumor-reducing to a tolerant phenotype through the checkpoint receptors cytotoxic T lymphocyte antigen 4 (CTLA-4) and lymphocyte activation gene 3 (LAG-3) [90].