ANALYSIS OF RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM FOR THE HLA-DR GENE IN JAPANESE PATIENTS WITH SARCOIDOSIS

Background - It is commonly assumed that some immunological disorder m ag play a part in the pathogenesis of sarcoidosis. Previous studies by several groups have shown a significant association with HLA-DR antig ens in patients with sarcoidosis. In this study, restriction fragment length polymorphism (RFLP) analysis of the HLA-DR gene was designed to confirm the association at the gene level and to look for a gene rear rangement which may influence susceptibility to sarcoidosis. Methods - Thirty two unrelated Japanese patients with sarcoidosis were tested f or HLA antigens and subjected to RFLP analysis after digestion with Ec o RI, Pst I, Pam HI, Pvu II, and Hind III by using an HLA-DR beta cDNA probe. A group of 47 unrelated healthy Japanese subjects served as co ntrols. Frequencies of each restriction fragment were compared between the patients and the control subjects. Correlation between fragment f requencies and clinical features were also analysed. Results - No rest riction fragments of HLA-DR beta gene were found specific to the patie nts with sarcoidosis. The RFLP analysis could detect polymorphism of H LA-DR beta genes that was not distinguishable by conventional serologi cal methods. Several restriction fragments of the DR beta gene were se en only in DRw52 positive individuals, and showed higher frequencies i n the patients than in control subjects. The patients with these DNA f ragments were likely to have limited stage disease with no ophthalmic involvement. Conclusions - An association between HLA and sarcoidosis was noted at the DNA level, although no restriction fragments were spe cific for this disease. RFLP analysis of the HLA gene is a more useful method than the usual HLA typing, and should be the first step in ide ntifying the gene sequence which is connected with susceptibility to s arcoidosis.