The Hr Factor 295 



antigen which results from the action of a single gene may be 

 indistinguishable serologically from that produced by the com- 

 bined action of two alleles. For example, gene R^ gives a posi- 

 tive reaction with antibodies Rho and Rh', as do also gene r^ and 

 R^ together. Thus a person with gene R^ will show the same re- 

 actions as an r^R' individual. Similarly, gene R- acts like r^ and 

 -R" together.* 



In Table 14 we have seen that eight Rh types are theoretically 

 possible. When the reactions of these eight to anti-Rh' and 

 anti-Rh" sera are considered, it is clear that these types fall into 

 four classes as in Table 15. These four classes are comparable 

 to the four Landsteiner or A-B blood groups. When anti-Rho 

 antiserum is also taken into account, each class can be further 

 subdivided into two subclasses — those that give a negative reac- 

 tion with anti-Rho antiserum and those that are Rho-positive. 

 This classification makes the relationship of the eight types 

 somewhat clearer. 



The rhesus blood types have been studied rather intensively 

 among the white population of New York City, and it has been 

 found that the frequencies of the various types are very different. 

 Some studies have shown that about 54 per cent have the Rh' 

 agglutinogen only, .14 per cent the Rh" agglutinogen only, and 

 about 17 per cent both these agglutinogens. Approximately 86 

 per cent possessed the Rho agglutinogen but only 2.5 per cent of 

 these lacked both the other agglutinogens. About 12 per cent of 

 the cases studied were Rh-negative. Of the eight theoretical 

 types of blood, all have been found, but the Rh'Rh" type is 

 exceedingly rare. 



The Hr Factor 



In 1941 Levine and Javert reported that when the blood of a 

 woman who was Rh-positive, but who had produced an erythro- 



* Originally, type rh^ was designated as type Rh. Because the term Rh 

 types is often used in a general sense, it was considered advisable to change 

 the designation of this specific Rh type to Rho. The gene was correspondingly 

 changed from Rh to Rh^ (Wiener, 1944). As it is more conventional to use 

 superscripts for multiple alleles, Rh^, R^ or r^ are preferable (Wiener et al., 

 1946). Genes R^ and R^ were formerly designated Rhi (or Rho') and Rh2 (or 

 Rho"), respectively. Antisera anti-Rho, anti-Rh', and anti-Rh" were formerly 

 designated anti-Rh, anti-Rhi, and anti-Rh2. 



