ASSOCIATION OF HLA-B39 WITH HLA-B27-NEGATIVE ANKYLOSING-SPONDYLITIS AND PAUCIARTICULAR JUVENILE RHEUMATOID-ARTHRITIS IN JAPANESE PATIENTS -EVIDENCE FOR A ROLE OF THE PEPTIDE-ANCHORING-B-POCKET

Objective. To investigate the characteristics of HLA-B27 that render s usceptibility to seronegative spondylarthropathies. Methods. Serologic HLA class I typing of Japanese patients with ankylosing spondylitis ( AS), juvenile rheumatoid arthritis (JRA), and healthy controls, was pe rformed. HLA-B39 subtypes were determined by polymerase chain reaction -sequence-specific oligohybridization. Results. HLA-B27 was present in 40 of 48 patients with AS (83%), and in only 1 of 210 healthy control s (0.5%). Three of 8 patients (37.5%) who were negative for HLA-B27 we re positive for HLA-B39, which was significantly higher compared with the HLA-B27-negative controls (6.2%; P = 0.01), Significant associatio n with HLA-B39 was also noted in the JRA patients (16.7%; P < 0.01), e specially in those patients with pauciarticular-onset disease (33.3%; P < 0.01). Ten of 13 HLA-B39-positive patients had subtype B3901 and 3 had B3902. Conclusion. Because HLA-B27 and HLA-B39 share Glu at pos ition 45 and Cys at position 67, both of which constitute components o f the peptide-anchoring B pocket, and because they possess similar pep tide-ligand motifs, our results may support either the role of the pep tides presented by class I antigens or the importance of Cys at positi on 67, in the development of spondylarthropathies and pauciarticular-o nset JRA.