A new qualitative variant of the RhE antigen revealed by heterogeneity among anti-E sera

We have recently detected a new qualitative variant of the RhE antigen characterised by negative reactions with a minority of anti-E sera, and an inability of the relevant cells to completely absorb most, if not all, anti-E samples that we tested. In tube tests, using a two-stage enzyme technique, cells from the proposita (V.R.) were completely agglutinated by 8 out of 12 undiluted polyclonal sera, weakly agglutinated (2+ and 3+ reactions) by 2 sera, but not agglutinated by the 2 remaining sera. Cross-absorption tests using 1 non-reacting, 1 weakly reacting and 4 strongly reacting polyclonal anti-E sera showed that V.R.'s cells only slightly reduced their anti-E titres versus r"r cells, whilst completely removing their reactivity against her own cells. Absorptions with R2R2 cells abolished activity against both cell types. The cells of V.R. failed to absorb or elute anti-Ew, and had normal expression of c. Three monoclonal human anti-E reagents were tested by fluorescence flow cytometry; one reagent failed to react with the cells of V.R., a second bound as strongly with V.R.'s cells as with R1R2 controls while the third bound much more weakly with V.R. than with any other E+ sample. The variant of RhE in the V.R. family is therefore distinct from Ew, and lacks an epitope recognised by a major constituent of most anti-E sera. This epitope is unlikely to be ET, since all of 91 samples from E-positive Australian aborigines (many of which are expected to lack ET) were agglutinated by a serum that failed to react with V.R.'s cells.(ABSTRACT TRUNCATED AT 250 WORDS)