a clinical case of weak a antigen on the erythrocytes in a person with coexistent anti-a antibodies

this study investigated a person with an ab0 discrepancy. her blood group initially typed at the birth as ab rh+ (positive); however, it was b rh+ (positive) or rh- (negative) when she was in her teens. at room temperature, her erythrocytes were agglutinated by anti-b, and the agglutination was significantly weaker at 37 °c. as a result, her erythrocytes did not absorb anti-b but anti-a. furthermore, her erythrocytes were agglutinated by anti-a at 37 °c with signs of hemolysis in the presence of complement. the unwashed erythrocytes were also agglutinated in an antiglobulin test by polyclonal anti-a at 37 °c and by heated polyclonal anti-a and anti-a mab 2-8 at room temperature. moreover, her serum agglutinated a erythrocytes at room temperature with less activity at 37 °c; however, it agglutinated b erythrocytes at 37 °c. the ability of the erythrocytes of this person to absorb anti-a came along with the agglutination of her erythrocytes at 37 °c by polyclonal serum and decreased activity of the serum to agglutinate a erythrocytes at 37 °c, compared to room temperature. the absence of anti-b absorbance by the person’s erythrocytes was accompanied by the presence of anti-b in the serum, which was active at 37 °c. the incubation of the person’s serum with 0 erythrocytes induced the ability of erythrocytes to absorb anti-a and to be hemolyzed by anti-a in the presence of complement in accordance with the person’s characteristics of erythrocytes. the reaction of absorption and agglutination at room temperature and 37 °c by heated serum with the use of complement may help to reveal both weak a and b antigens and anti-a and anti-b antibodies while ab0 blood typing.