COMPLETE NUCLEOTIDE-SEQUENCE OF HLA-B(ASTERISK)0703, A B7 VARIANT (BPOT)

HLA-B703 (BPOT) is a B7-like antigen segregating within families. To d etermine the complete B0703 nucleotide sequence, HLA-ABC-cDNAs derive d from the EBV cell line POT71 have been cloned. Four B0703-positive clones were sequenced to obtain an accurate consensus sequence. With r espect to the isoelectric focusing-identical HLA-B0702 allelic produc t, HLA-B0703 differed only in a cluster of four nucleotide substituti ons in exon 2 and a single (silent) nucleotide substitution in exon 3. The resulting amino acid substitutions in the alpha(1) domain of B703 at residues 63 (Ala --> Thr), 70 (Gin --> Asn), and 71 (Ala --> Thr) probably have their origin in a segmental exchange between B7 and othe r B alleles.