A NEW HLA-B44 VARIANT (B44BO [B-ASTERISK-4408]) IDENTIFIED BY SEROLOGY

Using HLA serology, we detected a new variant of HLA-B44 - B44BO - in two families. This antigen reacts with B44 antisera and is negative wi th over one-third of B12 (B44, B45) sera but reacts with 50% of antise ra with a B62 component, especially if they contain anti-B57. The vari ant, B4408, differs from the common B*4402 by 4 nucleotide substituti ons in exon 2: 193, 206 and 209, which produce changes in the alpha 1d omain at positions 41, 45 and 46 (TKE in B4402 and AMA in B44BO); and nucleotide 213, a silent substitution. At each of these positions, B 4408 is identical to B46, B*57 and many B*15 alleles. As anticipated from its predicted iso-electric point (5.71), one-dimensional isoelect ric focusing studies showed that B44BO focuses at the same position as B4402. The sequence and serological reactivity of this rare antigen allowed the identification of two likely epitopes shared by two differ ent groups of HLA-B antigens.