ABSTRACT
BACKGROUND: MAR (RH51), a high-incidence antigen in the Rh blood group system, is absent from RBCs with a double dose of CW or CX or a single dose each of CW and CX antigens, as well as from rare Rh phenotypes including D- - and Rh(null). The MAR antigen is associated with the presence of Ala36 and Gln41 on the RhCe protein. The original example of anti-MAR, described in 1994, was made by a DCWe/DCXe woman. It was possible that the antibody directed against a high-incidence antigen in the Rh system made by a DCXe/DCXe woman (CM) in 1983 was anti-MAR. CASE REPORT: A 52-year-old, multiply transfused, white woman (CJ) with pre-existing anti-c, -E, and -Jk(a) presented for preoperative work-up for her fifth open heart procedure. The strength of the reaction of her RBCs with anti-CW suggested a double dose of CW antigen. Her serum, which unexpectedly was strongly reactive with c-, E-, Jk(a-) RBCs by PEG indirect antiglobulin test, was incubated with E-c-, Jk(a-) RBCs, and an eluate was prepared. This eluate reacted 3+ with E-c-, Jk(a-) RBCs but did not react with Rh(null) (n = 5), - - (3), DCW- (2), Dc- (1), or DCWe/DCWe (1) RBCs. Two related DCXe/DCXe and two unrelated DCWe/DCXe RBC samples were weakly agglutinated. The patient's RBCs were negative with the original anti-MAR but reacted as strongly as the positive control RBCs with the antibody made by the DCXe/DCXe person. CONCLUSION: This is the first example of a MAR-like antibody made by a DCWe/DCWe woman. The specificity cannot be called anti-MAR, because some MAR-negative samples react, albeit weakly. The original anti-MAR, made by a DCWe/DCXe woman, did not react with DCWe/DCWe, DCWe/DCXe, or DCXe/DCXe RBCs. It is apparent that the specificity of "anti-MAR" differs slightly, depending on the CW/CX status of the antibody maker.
