Regulation of ectopic expression of HLA class II genes.

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To decipher the molecular mechanism of the association between HLA and autoinsune diseases, we have investigated the polymorphisms of HLA class I and class 11 genes in the coding and promoter regions. The highly polymorphic second exons of HLA-B. DRB1. DRBS, DRB4. DRB5. DRB6. DQA1. DQB1. DPAI. and DPBI genes were analyzed by the PCR-SSOP and PCR-SSCP methods. and 27, 51, 3.1.4.3.9.14.8. and 36 alleles. respectively. were defined. In addition, cytoplasmic exons of HLA-DRA and DQBL genes were found to be polymorphic, as well 9 allelic differences in the promoter region of the DQAL gene were identified. These polymorphisms were analysed in healthy individuals antipatients with several autoimmune diseases including IDDM. RA, Graves' disease. Behcet's disease, Takayasu arteritis, Hashim to hyroiditis. SLE. mixed connective tissue disease, and specific alleles were identified to be strongly associated with each disease. Moreover, the regulation of the HLA class 11 genes, especially their inductions by cytokinesis such as interferons and TNFs were investigated in detail. and it was found that the HLA-DQAL gene was differently regulated from the other class 11 genes by means of expressivity and inducibility via a DQAL gene-specific positive transcription factor NF-TRS. The binding sites of NF-TRS is overlapping with that of another transcription factor NF-Y and the polymorphism at the sites was found to affect the binding affinity for these factors. suggesting that the expression of the HLA-DQAL gene is allele-specific and may play a role in immune regulation and in developing the autoimmune diseases.