THE Rh CHROMOSOME FREQUENCIES IN ENGLAND

By R. R. RACE, M.R.C.S., L.R.C.P., A. E. MOURANT, B.M., B.Ch., MA., D. Phil., SYLVIA D. LAWLER, M.W, B.S., and RUTH SANGER, B.Sc.* T HIS paper reports the results of testing 1073 samples of blood, from English people, with the Rh antibodies anti-C, anti-C”, anti-c, anti-D, anti-E and anti-c. To these are added another 92.7, tested with anti-C, anti-c, anti-D and antiE, the results of which have been previously published.’ Professor Fisher has used the total iooo to estimate, by his method of maximum likelihood,2 the frequencies of the Rh chromosomes in England, and has very kindly allowed us to make use of his results. The discovery3 of the six elementary Rh antigens and their mutual relationships resulted from a study of the British work of 1943 on the isolation of the seven allelomorphs of the Rh gene. Fisher pointed out that the complex interactions of the four antibodies and seven allelomorphst known at that time could he most simply understood by assuming that each allelomorph was built up from three elementary antigens, each of which could exist in two alternative or allelomorphic forms. These three pairs of allelomorphic antigens were called C and c, D and d, E and e. A chromosome could carry any combination of the three pairs; it might carry, for example, CDe or cde, etc. Seven of the eight theoretically possible combinations could be identified with the seven allelomorphs already known. The eighth combination, CdE, has still to he isolated, but there is a theoretical reason why it may be very rare.’ As an individual has two sets of chromosomes, he has two Rh chromosomes and his genotype may be any combination, for example, CDe/cde. In this case his sex cells, which each contain only one chromosome of a pair, will carry either CDe or cde in equal numbers. The four known Rh zntibodies were thus renamed anti-C, anti-c, anti-D and anti-E. The antibodies anti-c and anti-d which the theory predicted were subsequently discovered,4 ‘ and as a corollary the existence of the predicted antigens e and d were confirmed in a positive manner. A third alternative to C and c, called C”, was found ‘in 1945. It has been isolated in the chromosome combination C”De and also C”de. Presumably the combinations C”DE and C”dE exist although they may be very rare. A third alternative to D and d, called D”, was recognized7 in 1946, and it has been detected in the combinations CD”e, cD”’E and cD”’e. Twelve different Rh chromosomes have now been identified; they are CDe, cde, cDE, cDe, C”De, cdE, Cde, CDE, CDIe, cD’E, cD”e, and C”de. These chromosomes can theoretically give rise to seventy-eight genotype combinations.