STRUCTURAL-ANALYSIS OF HLA-B40 EPITOPES

Two genes encoding HLA-B60 or HLA-B61 were cloned from Japanese and th e exons of their genes were sequenced. One silent mutation was observe d at the exon 1 between HLA-B60 (B40012) and B*40011. Seven nucleotid e substitutions were seen at the exon 3 between HLA-B61 (B4006) and B 4002. Three substitutions at codon 95, CTC in B*4002 to TGG in B*4006 , changed Leu in B4002 to Trp in B*4006, while two substitutions at c odon 97, AGC in B4002 and ACG in B*4006, changed Ser in B*4002 to Thr in B4006. Since B*4002 shares the epitope of alloantibodies specific for HLA-B61, two HLA-B61 subtypes are discriminated by two amino acid substitutions at residues 95 and 97. B40012 and B*4006 differ by fou r amino acid substitutions on the beta sheet and five amino acid subst itutions on the alpha2 helix. Since the residues at the beta sheet see m hardly to affect the binding of alloantibody, it is suspected that t he residues on the alpha2 helix provide epitopes for alloantibodies th at discriminate allospecificity between HLA-B60 and HLA-B61.