Screening by allele-specific primer PCR (ASP-PCR) for these mutations among 100 Caucasian and 100 Black random blood donors indicated allele frequencies of 2 . 5% and 0%, respectively. Ala100Thr alone was present in 33% of the Caucasians (but none of the Blacks) with no weakening of FY expression.A novel allele at the FY locus associated with the Fy x phenotype was studied. Mistyping of this weak Fy b antigen in clinical transfusion medicine may lead to delayed haemolytic transfusion reactions in immunized patients. A potential role for genomic typing is proposed.

Summary Flow cytometric analysis of eosin‐5‐maleimide (EMA) binding to red cells is a screening test for the diagnosis of hereditary spherocytosis (HS). The present study used chemical modifications to determine the integral membrane proteins that react with EMA. The predominant interaction of EMA, contributing c. 80% of fluorescence, was with the ɛ‐NH2 group of lysine in band 3 protein, as previously reported. The remainder of the EMA fluorescence was attributable to labelling of accessible sulfhydryl groups on intact red cells. This reaction was heat labile. Three molecules containing sulfhydryl groups were shown to be associated with the Rh blood group protein complex by sodium dodecyl sulphate polyacrylamide gel electrophoresis. These were CD47 and the Rh‐associated glycoprotein, both in the Mr 40–60 kD region, and the Rh blood group proteins in the 30–32 kD region. Immunoprecipitation, using specific monoclonal antibodies and antibody binding studies by flow cytometry, showed that the relative content of these three membrane proteins was lower in HS than normal red cells. Thus, the high predictive value of the EMA binding test for HS reflects changes in the relative amounts of the Rh‐related integral membrane proteins as well as band 3 in HS red cells.

Lutheran glycoprotein (Lu gp) has five predicted immunoglobulin superfamily (IgSF ) domains. K562 cells were transfected with Lu cDNA and tested by flow cytometry with monoclonal antibodies and Lu blood group antisera. The results confirmed the identity of Lu cDNA. Deletion mutants lacking the regions encoding one or more IgSF domains were made by inverse polymerase chain reaction (PCR), expressed in K562 cells, and tested with the same antibodies. The Lub and Lu5 antigens and the epitope recognized by monoclonal antibody BRIC 224 were mapped to the first, N-terminal, IgSF domain. Lu4 and Lu8 were mapped to domain 2; Lu20 to domain 3; Lu7 and BRIC 221 epitope to domain 4, and Lu13 and Aub to domain 5. The organization of the LU gene was determined. The region encoding the open reading frame is arranged in 15 exons extending over ≈11 kb on chromosome 19q13.2. The Lua/Lub and Aua/Aub blood group polymorphisms were studied using genomic DNA from typed blood donors. The Lua mutation is a base change in exon 3 (G252 to A) encoding an Arg77 (Lub) to His (Lua) change on the CFG face of domain 1. The Aua/Aub polymorphism is an A1637 to G substitution in exon 12 encoding a Thr539 (Aua) to Ala (Aub) change on the G strand of domain 5.

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