Abstract Background The clinically significant antibody anti‐A,B together with anti‐A and anti‐B has been known for many decades to be present in blood group O plasma. As anti‐A,B is only reactive when an A or B antigen is present, its contribution to titer cannot be easily distinguished from anti‐A and/or anti‐B. Study Design and Methods Chemically synthesized AB epitope (ABep) was attached onto red cells creating ABep‐kodecytes; methodology was optimized and then used together with group A‐ and B‐kodecytes to semi‐quantitative undiluted plasma samples of all ABO blood groups for anti‐A, anti‐B, and anti‐A,B. Standard titers with plasma dilutions against natural A 1 and B cells were performed in parallel. Results ABep20‐kodecytes were able to semi‐quantitate anti‐A,B independently of anti‐A and anti‐B. Anti‐A and anti‐B levels were also able to be inferred by deduction of the anti‐A,B contribution. There was a large range in the levels of anti‐A,B in the group O samples, including in those determined to have high‐titer ABO antibodies. Unexpectedly, some group A, B, and AB individuals were also found to have an anti‐A,B‐like antibody. Discussion Anti‐A,B is a much more complex antibody than current understanding, and shows a range of activity over a large continuum, which includes in vitro detectable anti‐A,B‐like antibodies in non‐group O samples. The ability to measure anti‐A,B independently of anti‐A and anti‐B levels may be useful in evaluating clinical associations.
Henry et al. (Thu,) studied this question.