EXPRESSION AND QUANTITATIVE VARIATION OF THE LOW-INCIDENCE BLOOD-GROUP ANTIGEN HE ON SOME S-S- RED-CELLS

Background: Red cells devoid of glycophorin B (GPB)-borne S, s, and U antigens are classified as an S-s-U- or S-s-U variant (U+(var)) and ca n arise from deletion and nondeletion genetic backgrounds. In nondelet ion forms of S-s-U-, little information is available on whether the al tered GPB gene (GYPB) is expressed in red cells. Study Design and Meth ods: Red cells classified as S-s-U- or S-s-U+(var) were tested with an ti-U, anti-U/GPB, anti-He, and anti-N by hemagglutination. Selected sa mples were tested by flow cytometry, immunoblotting, and polymerase ch ain reaction amplification using allele-specific primers. Results: He (MNS6) was found on 23 percent (20/87) of samples. These and another 2 1 of the 87 samples were agglutinated by an anti-U/GPB reagent; this i ndicated that approximately 50 percent of S-s- samples possessed GPB v ariants. The strength of He varied among the samples. Genomic polymera se chain reaction with allele-specific primers showed the presence of expected DNA GPB-like products encoding He. Immunoblotting showed that He was carried on a membrane component with a relative molecular mass indistinguishable from that of GPB. Conclusion: The finding of He on S-s- red cells provides direct evidence for the presence of an altered form of GPB in red cells previously thought to be devoid of this glyc ophorin. Quantitative variation in He antigen expression was observed in a subset of S-s- red cells.