Bu and SV: Two Closely Related B‐Locus Specificities

The B15/Bw21/Bw35 related specificities "Bu" and "SV" have been studied in Bristol and in Leiden, both independently and with mutually exchanged sera and cells. Evidence is presented that these specificities are likely to be discrete though very closely related antigens occurring with a combined phenotype frequency of about 1% in Dutch and English Caucasians. SV may be associated with Aw36, while no clear-cut haplotype or phenotypic association has yet emerged for Bu with any HLA--A sor C locus antigen. Bu and SV appear to be related to the variant of B15 reported to be common in Negroid populations.