Bu--a new antigen at the HLA-B locus.

Evidence is presented for a new allele at the HLA--B locus defining a new antigen, Bu. Population studies indicate a gene frequency of 0.0043 in English Caucasians. No HLA--B locus triplets involving the Bu antigen have been observed. Inheritance of Bu has been established in three informative families, each of at least three generations. Platelet absorption studies and analysis of a large number of multispecific HLA--B antisera suggest that Bu is "intermediate" between the well-established antigens Bw15 and Bw21.