Flow cytometric studies of the D antigen of various Rh phenotypes with particular reference to Du and Del.

Flow cytometric analysis was performed on red cells (RBCs) to compare the antigen activity of various Rh phenotypes, including the rare variants Del and Du (both high-grade and low-grade), whose genotypes were confirmed or presumed by the family study. This appears to be the first report that the Del phenotype is due to the inhibitory effect of Cde. This study also compares the quantity of the D antigen in different phenotypes, whose genotypes comprise the same Du gene (cDuE) transmitted in a family. RBCs were stained by the indirect immunofluorescence method using IgG anti-D purified through a protein-A affinity column. The mean fluorescence intensity obtained for each genotype representing the activity of the D antigen decreased in the following order (percentages show relative fluorescence intensity taking cDE/cDE control as 100% and Cde/cde as 0%): CDe/cDE, 76 percent; CDe/cde, 73 percent; cDE/Cde, 70 percent; cDE/cDuE, 68 percent; CDe/Cde (high-grade Du), 59 percent; cDuE/cde (low-grade Du), 6 percent; and cDuE/Cde (Del), 3 to 4 percent.