Quantitative Serologic and Isotopic Studies on the Rho Variant--Du

1. Type D^u cells take up less than 10 per cent of the I-131 anti-D boundto 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 D^u cells results in an almost threefold increasein the uptake of I-131 anti-D, whereas, D negative cells show no consistentincrease after such treatment. Enzyme modification, therefore, serves to clearlydelineate the two cell types.

3. The range of uptake of I-131 anti-D to enzyme treated D^u cells is fromapproximately 7 to 17 per cent of that by R₁R₂ cells. Most of these results wereobtained from studies on Mendelian D^u types. Studies on several bloods frommembers of a family having Rh genotypes typical of the "gene interaction" D^uconfiguration (C in transposition to D) revealed no significant reduction inI-131 anti-D uptake when compared with D positive cells.

4. Decreased antibody binding to D^u cells was confirmed by the serologicmethods used. Absorption of an anti-D serum and antiglobulin inhibitionwith sensitized D^u cells indicated that the quantity of D antigen was lessthan that observed with the isotopic technic. Elution studies did not show asmarked a reduction of D antigen on the D^u cell as the other serologic technicsindicated. Possible reasons for these differences have been discussed.

5. Although, from both the serologic and isotopic studies, the data indicate that the type D^u red cell is quantitatively deficient in D antigen, theyare inadequate to rule out other explanations for their reduced D antigenactivity. Irrespective of the mechanism(s) responsible, the effective bindingof anti-D by D^u cells is reduced several fold; this would appear to be theprimary cause of the weak second stage of red cell antigen-antibody reactionwhich characterizes type D^u blood.

Submitted on July 28, 1964 Accepted on October 8, 1964