ATG is an abbreviation for a drug whose full name is anti-human thymocyte lymphocyte globulin. ATG is mainly indicated for immune rejection and prophylaxis in clinical organ transplantation and for the treatment of graft-versus-host reaction in bone marrow transplantation for the prevention of heavy aplastic anemia and pure red aplastic anemia. ATG can also be tried for autoimmune hemolytic anemia, primary thrombocytopenic purpura, and other immune diseases.Why does ATG have the above effects? Because ATG inhibits the activation of lymphocytes after antigen recognition and specifically destroys lymphocytes, which is equivalent to destroying the immunity of T cells in the body, so it can have an anti-rejection effect. In the process of using ATG, anaphylaxis may occur, so it is important to monitor the reaction. In addition, ATG is contraindicated in patients with allogeneic protein allergy and in patients with severe viral infections, systemic mycobacterial infections, malignant tumors, and immunocompromised conditions.