Rh sytem. Genetics and function.

Little is known about the exact genetic control of the Rh system. The Rh antigen is a large protein molecule carrying many antigenic determinants. The structural genes controlling its production comprise a gene complex that has probably evolved by unequal crossover and mutation at the duplicated points. No convincing evidence for crossing-over within the gene complex has been found since the discovery of Rh. Studies of Rhnull families provide evidence for unlinked control genes that influence the ability of the structural Rh genes to function. It was hoped that the Rhnull bloods would provide information to establish the function of the Rh antigen, because the antigen appears to be necessary to maintain the integrity of the red cell membrane. However, the abnormalities of the Rhnull cells (increased Na+K+ pumps) have not been tied directly to their lack of Rh antigens.