In 1981, Lymphocyte Immunotherapy (LIT) was performed to treat four URPL patients for the first time, based on the “tolerance” of human kidney allografts, three delivered normal babies and one delivered a premature baby . Since then, LIT have been widely used in patients for alloimmune type RPL, within and outside controlled trials. It attributes to the production of Anti-paternal Cytotoxic Antibodies (APCAs) in women with RPL. Subsequently, many studies confirm the association between recurrent abortions and parent similarity of Human Leukocyte Antigens (HLA) which induces hyporesponsiveness and inhibits production of blocker antibodies as immunological regulators to maintain the pregnancy. Anti-paternal Cytotoxic Antibodies (APCAs), Anti-idiopathic Antibodies (Ab2), and Mixed Lymphocyte Reaction Blocking Antibodies (MLR-Bf) are considered as a part of regulators that cover paternal HLA molecules in the surface of fetuses and make a barrier for attacking the maternal T cells and NK cells .