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The concentrations of anti-A and anti-B IgM and IgG antibodies have been studied in the serum of a patient with blood group AB who received a type A donor liver. A newly developed ABO-ELISA was used for this purpose and the values were compared to hemagglutination titers. During the postoperative study period over 8 weeks, the anti-A and anti-B levels showed a higher fluctuation than was measured in preoperative samples. Thus, in this AB-type patient, anti-A IgM varied 10-fold, anti-A IgG 20-fold and anti-B IgG 16-fold. Peak values corresponded to rejection episodes. Immunoactivation in the patient was further documented by the presence of abnormally high levels of soluble interleukin-2 receptors (slL-2R) in serum samples. The study shows that monitoring of anti-A/B antibodies may represent a further criterion to follow-up transplanted patients during the critical postoperative graft acceptance period.

A micro enzyme-linked immunosorbent assay (ELISA), using lyophilized stroma as carrier of red blood cell antigens, which stays stable longer than usual, using intact erythrocytes, was developed for determination of blood-group antibodies in the ABO, Kell and Lewis-systems. Stroma being fixed on microtiter plates was incubated with antisera and peroxidase-conjugated anti-human globulin. The transformation of the substrate added was determined photometrically. A binding of antibodies to the stroma could be demonstrated up to an antibody dilution of 1:1024 for the ABO-system, of 1:512 for the Kell-system and of 1:64 for the Lewis-system. By standardization of this method the quantitative determination of antibodies becomes possible without being restricted by the limited stability of intact erythrocytes.