Blood group antibodies are generally divided into two categories, natural antibodies and immune antibodies. Generally natural antibodies are lgM and immune antibodies are lgG. lgG class antibodies in most cases do not agglutinate with red blood cells with corresponding antigens in saline media, but only in colloidal media, enzymes and antiglobulins, and coagulant amine media, which are mainly blood group antibodies such as Rh, Kidd, and Duffy. Usually the condition produces antibodies through immunization, also known as immune antibodies. Most of the extravascular hemolysis occurs, and the optimal reaction temperature for such antibodies is 37°C, also known as warm antibodies.