A "normal" individual with a positive direct antiglobulin test: case complicated by pregnancy and unusual autoantibody specificity.

A "normal" individual with a positive, direct antiglobulin test is described. In common with many other "normal" persons in whom a similar finding has been made, there was no evidence of an increased rate of in vivo red blood cell destruction in this patient. The patient successfully completed a pregnancy during the time that detailed serologic studies on her autoantibodies were being performed. Although the maternal autoantibodies were demonstrable in both an eluate made from the red blood cells of her newborn infant, and in the cord serum, there was no reason to believe that the antibodies caused red blood cell destruction in the infant. The case was of further interest because of the specificities of some of the autoantibodies. Although the mother and child were both C-negative, eluates from their red blood cells contained what ostensibly appeared to be anti-C. Studies that showed that the antibody could be totally adsorbed with C-negative, as well as C-positive red blood cells, proved that this was another example of an autoantibody mimicking an alloantibody. Although this autoantibody appeared initially to have anti-C specificity it was eventually shown to be more closely related to anti-Hr or anti-Rh34, than to anti-C.