A MAR-like antibody in a DCWe/DCWe person

BACKGROUND: MAR (RH51), a high-incidence antigen in the Rh blood group system, is absent from RBCs with a double dose of C W or C X or a single dose each of C W and C X 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 DC W e/DC X e woman. It was possible that the antibody directed against a high-incidence antigen in the Rh system made by a DC X e/DC X e 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-C W suggested a double dose of C W 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), D- -(3), DC W - (2), Dc- (1), or DC W e/DC W e (1) RBCs. Two related DC X e/DC X e and two unrelated DC W e/DC X e 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 DC X e/DC X e person. CONCLUSION: This is the first example of a MAR-like antibody made by a DC W e/DC W e woman. The specificity cannot be called anti-MAR, because some MAR-negative samples react, albeit weakly. The original anti-MAR, made by a DC W e/DC X e woman, did not react with DC W e/ DC W e, DC W e/DC X e, or DC X e/DC X e RBCs. It is apparent that the specificity of anti-MAR differs slightly, depending on the C W /C X status of the antibody maker.