Association between HLA-DQA1, -DQB1 gene polymorphisms and susceptibility to asthma in northern Chinese subjects.

OBJECTIVE: Human leukocyte antigen (HLA) class II genes, especially HLA-DQ genes, which are highly polymorphic, have been thought to be candidate loci for the etiology of asthma, and shown to be involved in antigenic presentation. This study was conducted to investigate whether susceptibility or resistance to asthma is associated with HLA-DQA1 and DQB1 genes polymorphism.
METHODS: Venous blood samples were collected from northern Chinese population with Han ethnic. (1) One hundred and twenty-five unrelated asthmatic individuals and 52 subjects from 12 asthmatic pedigrees. (2) Ninety-six healthy controls without asthma and atopy with the same ethnic. Genomic DNA was extracted using standard phenol-chloroform method. The second exon of HLA-DQA1 and DQB1 genes were amplified by sequence-specific primer-polymerase chain reaction (SSP-PCR) method. All asthmatics had their serum IgE (total and specific) antibody or skin-prick test measured, bronchial reactivity to methacholine (Mch) and bronchial reversibility by beta(2)-agonist evaluated.
RESULTS: HLA-DQA1 * 0104 allele and HLA-DQB1 * 0201 allele were significantly higher in asthmatics than those in healthy controls (0.408 vs 0.177, P < 0.01; 0.568 vs 0.198, P < 0.01). Odds ratios (ORs) were 3.203 (95% CI 1.699 - 6.037), 5.328 (95% CI 2.883 - 9.849) respectively. Conversely, HLA-DQA1 * 0301 allele and HLA-DQB1 * 0301 were significantly decreased in asthmatics compared to healthy controls (0.296 vs 0.50, P < 0.01; 0.4 vs 0.563, P < 0.05); Logistic regression analysis showed that HLA-DQA1 * 0104 allele was associated independently with asthma etiology, OR [represented by Exp(B)] was 5.0942 with 95% CI 2.2520 - 21.1813; Spearman's analysis showed that HLA-DQA1 * 0104 allele and HLA-DQB1 * 0201 allele were positively associated with atopy, the correlation coefficient were 0.183 and 0.289 respectively, P < 0.01. By contrast, HLA-DQA1 * 0301 allele was negatively related to atopy, the correlation coefficient was -0.168, P < 0.05; linkage analysis did not support the view that HLA-DQA1/DQB1 genes were linked to asthma with LOD value being 0.72.
CONCLUSIONS: HLA-DQA1 * 0104 allele and HLA-DQB1 * 0201 allele were implicated in susceptibility to asthma and atopy, HLA-DQA1 * 0301 allele and HLA-DQB1 * 0301 might be protective factor against asthma. Asthma and atopy are multifactorial disorders, HLA-DQA1 and DQB1 genes are involved in the regulation of immune specific response to common allergen.