CTLA4 and Autoimmunity: In immunotherapy, drugs act at variousimmunological checkpoints of the body, recognized as several coinhibitoryand costimulatory receptors and their ligands that act, under normalconditions, to protect the body against autoimmunity, allergies, andinfectious diseases. Among them, theimmune checkpoint block (ICB) of targets such as PD-1/PD-L1 (programmedcell death protein 1 and programmed cell death-ligand 1) and CTLA-4(cytotoxic T-lymphocyte-associated antigen 4) stands out.