Some observations on the blood factor RhA of the Rh-Hr blood group system

Abstract

SUMMARYThe complex serologic behavior of the Rh-Hr agglutinogens has been underlined by the recent discovery that, with very rare exceptions, associated with blood factor Rh0 of Rh-positive blood, there are numerous other blood factors which we designated RhA, RhB, RhC. Rare Rh-positive individuals exist whose bloods have blood factor Rh0 but lack one or more of the other components. Such individuals can and have become sensitized to the missing blood factor. For example, in the case of an Rh-positive individual lacking blood factor RhA, anti-RhA may be produced. So, too, when RhB and RhC, are lacking, anti-RhB or anti-RhC may be produced. In fact, all 3 have been identified. The resulting anti-RhA, anti-RhB and anti-RhC serums are indistinguishable from “standard” anti-Rh0 serum in parallel tests on a random series of blood specimens, unless the series happens to include one of the rare Rh-positive bloods lacking blood factor RhA (type Rh0a or type Rh1a, etc.).In the present paper, anti-RhA serum from a sensitized type Rh1a mother whose child had erythroblastosis was used for studies on the distribution and heredity of the RhA blood factor. In addition, attention is called to the fact that Unger and Wiener have identified anti-RhB and anti-RhC although they are reporting at this time their studies with anti-RhA. A total of 2012 blood specimens from Rh0-positive individuals were tested; 951 from Caucasoids and 918 from Negroids. In tests on blood from Caucasoids, a “standard” Rh0 blood factor was invariably associated with a “standard” RhA blood factor. In no instance where the reactions with anti-Rh0 serums were typical was the RhA factor absent or a variant. However, if the Rh0 factor was a variant, 3 possibilities with regard to factor RhA were identified. Either factor RhA was “standard”, or factor RhA was a variant, or factor RhA was absent. This last possibility rarely occurs in Caucasoids since in our series only 1 Caucasoid blood or 0.1 percent lacked RhA blood factor and in that case the Rh0 factor was a variant.Among the 918 Rh-positive blood specimens from Negroids examined the situation was found to be somewhat different. While a “standard” Rh0, was almost always associated with a “standard” RhA, in 0.9 percent the RhA factor was absent. Among bloods with a Rh0 variant blood factor, just as with Caucasoids, all 3 possibilities were identified, namely bloods with “standard” RhA, with RhA variant, and also bloods with blood factor RhA absent. The incidence of Rh-positive bloods lacking factor RhA was considerably higher among Negroids than among Caucasoids, namely, 1.6 percent in Negroids, as compared with only 0.1 percent in Caucasoids.One interesting family was studied. The father's blood had the “standard” Rh0 blood factor, but lacked the RhA component (type Rh0a). The mother's blood had the Rh0 variant blood factor, and also lacked blood factor RhA (type ). The child's blood was of the same type as its mother, namely, Rh0 variant and lacking blood factor RhA (type ). The possible genetic explanations for these observations and their clinical significance were discussed.