Acquired changes of red blood cell ABO antigens

Objective: Pathological changes of the ABO antigens on red blood cells are rare events, but they are important in blood group serology because of the risk of false results in ABO typing. This review is designed to show these pathological changes and the problems in ABO testing caused by them, especi ally if monoclonal reagents are used. Sources: Selected literature and own experiences. Results: The most relevant pathological changes of the ABO ant igens are: 1) The depression of the A- and/or B-antigen on some or (nearly) all red blood cells of some patients with leukemia or myeolodysplastic syn drome. This change is caused by a reduced activity of ABH glycosyltransfera ses. 2) The acquired B-antigen in some patients with gastrointestinal disea ses and/or bacteremia. It is caused by a deacetylation of the A-antigen lea ding to a B-like antigen. 3) The 'acquired A-like antigen' in cases of Tn p olyagglutinability which is caused by the cross-reactivity of some anti-A r eagents with the Tn antigen. It has been found in cases of leukemia, but al so in healthy persons. Conclusions: Although reagents of high quality are u sed for ABO typing, testing for ABO isoantibodies in the serum is still ind ispensable. Monoclonal antibodies that are cross-reactive with the acquired B-antigen or with Tn-positive red blood cells should not be used for ABO t yping.