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Genetic contribution of major histocompatibility complex class II region to type 1 autoimmune hepatitis susceptibility in Venezuela


Paolo Tassinari, MD, Instituto de Inmunología, Universidad Central de Venezuela, Los Chaguaramos, Caracas, Venezuela
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Aims: Autoimmune hepatitis (AIH) is a progressive liver disease characterized by the presence of circulating autoantibodies, hypergammaglobulinaemia and a favourable response to immunosuppressive treatment. Although the pathogenesis of type 1 AIH is unknown, disease susceptibility is partially determined by genes linked to the class II region of the major histocompatibility complex. Type 1 AIH has been associated with DRB1*03, DRB1*04 and DRB3 alleles in European and North American Caucasians, with DRB1*0405 in Japanese, with DRB1*0404 in Mexican, and with DRB1*1301 in Argentinean populations.

Methods: To analyse the molecular basis of these associations in Venezuela (mestizo population), we examined the frequency of human leucocyte antigens (HLA)-A -B -C, HLA-DQ and HLA-DR genes by low- and high-resolution oligonucleotide typing in a population of 41 type 1 AIH patients and 111 ethnic- and aged-matched healthy subjects.

Results: The frequencies of both DRB1*1301 (P<0.0001) and DRB1*0301 (P<0.005) were significantly higher in patients than in controls. In addition, patients showed a strong association with the DRB3 allele (P<0.01). In contrast, the DQB1*04 allele was significantly decreased in the patient group (P<0.01). The frequencies of haplotypes A*01-B*08-DQB1*02-DRB1*03-DRB3, DQB1*05-DRB1*1301, DQB1*06-DRB1*1301 and A*02-DRB1*1301, B*45-DRB3 were significantly increased in type 1 AIH patients compared with the controls (P<0.01).

Conclusions: In conclusion, our data indicate that type 1 AIH predisposition in a Venezuelan mestizo population of different ethnic backgrounds is associated with DRB1*1301 and DRB1*0301 alleles. In addition, our findings suggest that protection against disease might be conferred by the DQB1*04 allele, with distinct ethnic differences from other populations.