Quantitative Serologic and Isotopic Studies on the Rho Variant—Du

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Abstract
1. Type Du cells take up less than 10 per cent of the I-131 anti-D bound to D positive cells, so that the quantity of cell bound I-131 did not differ significantly from that bound nonspecifically to D negative cells. 2. Papain modification of Du cells results in an almost threefold increase in the uptake of I-131 anti-D, whereas, D negative cells show no consistent increase after such treatment. Enzyme modification, therefore, serves to clearly delineate the two cell types. 3. The range of uptake of I-131 anti-D to enzyme treated Du cells is from approximately 7 to 17 per cent of that by R1R2 cells. Most of these results were obtained from studies on Mendelian Du types. Studies on several bloods from members of a family having Rh genotypes typical of the "gene interaction" Du configuration (C in transposition to D) revealed no significant reduction in I-131 anti-D uptake when compared with D positive cells. 4. Decreased antibody binding to Du cells was confirmed by the serologic methods used. Absorption of an anti-D serum and antiglobulin inhibition with sensitized Du cells indicated that the quantity of D antigen was less than that observed with the isotopic technic. Elution studies did not show as marked a reduction of D antigen on the Du cell as the other serologic technics indicated. Possible reasons for these differences have been discussed. 5. Although, from both the serologic and isotopic studies, the data indicate that the type Du red cell is quantitatively deficient in D antigen, they are inadequate to rule out other explanations for their reduced D antigen activity. Irrespective of the mechanism(s) responsible, the effective binding of anti-D by Du cells is reduced several fold; this would appear to be the primary cause of the weak second stage of red cell antigen-antibody reaction which characterizes type Du blood.