Anti‐Rh33, the second separable example, also made by a person who made anti‐D and has C+ red cells

A complex serologic investigation resulted in identification of the second example of separable anti-Rh33. A patient who had been transfused frequently and who had red cells that lacked a portion or portions of the D mosaic of antigens made anti-D against that portion of D missing from her red cells, anti-c, anti-V, anti-Rh33, anti-K, and an autoantibody that mimicked the reactions of anti-D. Differential adsorption experiments showed that the anti-Rh33 was separable from the other antibodies present. The serologic findings in this case and in the study in which anti-Rh33 was first found show some sort of relationship between D and Rh33. First, one of the genes, RoHar, that makes Rh33 makes a form of D that is difficult to detect. Second, the only other gene thus far known to make Rh33, DIV (C)-, encodes for a form of D from which portions of the D mosaic are missing. Third, both examples of separable anti-Rh33 were made by women who made anti-D and whose red cells were C+.