Objective. Atopic asthma provides a useful model for evaluating the genetic factors that control human immune responsiveness. HLA class Ⅱ gene products are involved in the control of immune response. As HLA-DRB gene is the most polymorphic HLA class Ⅱ gene, we investigated whether susceptibility or resistance to the disease is associated with HLA-DRB. Methods. Blood samples were obtained from two groups of unrelated Chinese northern adults: （l） 50 atopic asthma （7 of them with familial aggregation） ;（2） 80 healthy controls without asthma or atopy and other HLA-associated diseases. Genomic DNA was extracted from peripheral venous blood leucocytes. The polymorphic second exon of HLA-DRB gene was amplified by sequence-specific primer polymerase chain reaction （SSP/PCR） methods. All patients had their serum IgE （total and specific） antibody levels by RAST, bronchial reactivity assessed by methacholine brocho-provocation test and/or bronchodilation test. Results. There was an increased gene frequency of DR6（13） and DR52 in asthmatic subjects compared with healthy subjects（17% vs 4. 3%, P<0.01; 50% vs 17. 5 %, P<0. 01 ）, and the decreased frequency of DR2（15） and DR51 in asthmatic patients（7% vs 18%, P<0. 05; 2 % vs 33 %, P<0. 01 ）. We found the positive association between DR6（13）-DR52 and sIgE antibody responsiveness to dl （from house dust mite al- lergen ）; negative association between HLA-DRB alleles and TIgE or BHR （bronchial hyperresponsiveness ）. Conclusion. The results suggested that HLA haplotype DR6（13）-DR52 was significantly implicated in sus- ceptibility to house dust mite induced-asthma, at least it would be more closely associated with atopic asth- ma. Conversely, alleles DR2（15） and DR51 might confer protection against the disease. HLA-DRB genes were particularly involved in regulating human atopic immune response in asthma.
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