Critical re-examination of the specificity of auto-anti-Rh antibodies in patients with a positive direct antiglobulin test.

Forty-eight autoantibodies with apparent 'simple' anti-Rh specificity (anti-e, -E, -c, -D, -C, -Ce, -G), have been studied by means of multiple absorption tests. The finding that 34 (70.8%) of these antibodies could bind to red blood cells lacking the antigens that the antibodies appeared to define, indicated that the antibodies had different specificities than seemed to be the case in initial antibody identification tests. Those autoantibodies that at first appeared to be directed against the Rh antigens e, E or c, most often had anti-Hr or anti-Hro specificity. These data explain why some apparent anti-Rh autoantibodies can be eluted from the red blood cells of patients negative for the antigens that the antibodi:s appear to define. However, they also illustrate that the phenomenon of autoantibodies mimicking specificities that they do not possess is common in patients positive for the antigens against which their autoantibodies appear to be directed. An explanation for the mode of action of these autoantibodies in complexing with the Rh agglutinogen is proposed, and the significance of the antibodies in transfusion therapy is considered.