Determination of zygosity using flow cytometric analysis of red cell antigen strength.

A flow cytometry method, developed in our laboratory to measure red cell (RBC)-bound IgG, was compared to the manual titration technique in the measurement of RBC antigen strength to determine zygosity. Parallel studies using antibodies to antigens in the Rh, Kell, Kidd, Ss, and Duffy systems were performed. The antisera (n = 20) were tested against five examples each of RBCs from apparent homozygotes and heterozygotes. The flow cytometry method was clearly superior, showing distinct differences, with no overlap of the ranges of results, between the reactions of RBCs from homozygotes and heterozygotes with 10 of 20 (50%) antisera. By the manual titration technique none of these sera clearly demonstrated dosage and 15 showed overlap of the ranges. It was obvious from the results that the commonly used manual titration technique for comparing the test RBCs with a single example of RBCs from a homozygote and heterozygote yielded inaccurate results.

Immunohematologic consequences of major ABO-mismatched bone marrow transplantation.

Twelve of 58 (21%) evaluable patients of blood group 0 who received a bone marrow transplant (BMT) from an HLA-matched sibling of a donor of group A or B developed significant immunohematologic problems in the posttransplant period. Anti-A or anti-B isohemagglutinins persisted for longer than 120 days post-BMT in nine patients and are still present in three patients at days +162 to +605. Red cell production as indicated by a reticulocyte count of greater than 0.5% was delayed to 40 days or more in nine patients, and in five of these was markedly delayed to 170 days or longer. One patient does not as yet have red cell production on day +605 in spite of having had 13 plasma exchanges performed to reduce the anti-B titer. Five patients experienced overt hemolysis, manifested by a sudden drop in hemoglobin of 1.5 to 4 gm/dl (median = 2.5 mg/dl), starting on day +37 to +105 (median = +65), persisting for 10 to 94 days (median = 36 days). Hemolysis and a delay in the onset of erythropoiesis beyond 170 days were more frequent in 30 patients treated with cyclosporine/prednisone than in 28 patients treated with methotrexate/prednisone for graft-versus-host disease prophylaxis. Our data indicate that ABO major mismatched BMT can be associated with significant immunohematologic consequences, some of which occur more frequently in association with cyclosporine administration.

High-titer, high-thermal-amplitude cold autoagglutinin not associated with hemolytic anemia.

An example of an unusual cold autoagglutinin is reported. The antibody was monoclonal IgMKappa able to fix complement, and, in the presence of albumin, had both a high titer (greater than 4,096 at 4 degrees C) and a wide thermal range (4-37 degrees C). The patient was closely followed over a 3-year period with no evidence of hemolysis ever documented, despite a persistently positive direct antiglobulin test and the presence of the cold autoagglutinin. In contrast to previous reports regarding cold-agglutinin disease, this case demonstrates that in vivo hemolysis is not always associated with cold autoagglutinins that in vitro show a high thermal range in the presence of albumin.