CD80 and neoplasm: These processes are mediated by at least three mechanisms: (i) suppression of reactive T lymphocytes activation by PD-L1 binding to PD-1 receptor present on tumor cells surface; (ii) resistance of tumor cells to CD8+ T cells and cell lysis mediated by binding of the Fas receptor to its ligand, Fas ligand (FasL), and (iii) interaction of PD-L1 with CD80 of activated T cells, acting as an inhibitor of cell activity (9).