The Rhesus Factors—I: Serology

Human red blood corpuscles contain many antigens besides the A and B factors, those of greatest clinical importance being the Rb factors. The first of these factors was discovered by Landsteiner and Wiener (1940), and was so called because a similar factor is present in the corpuscles of the Rhesus monkey. This factor is demonstrable in the corpuscles of 85 per cent, of Europeans an^ white Americans, who are said to be Rh-positive. The remaining 15 per cent, lacking this factor are known as Rh-negative. When the agglutinogens A or B are absent from the corpuscles the corresponding antibodies, anti-A or anti-B, are present in the plasma (see Fig. I). The Rh factor differs from the A and B factors in that no natural Rh antibodies, anti-Rh, are found in the plasm*1 of Rh-negative blood. Such antibodies may appear, however, as the result of immunization.