ABSTRACT
BACKGROUND: Specific IgE responses to allergens provide useful models for evaluating the genetic factors that control human immune responses. HLA class II gene products are involved in the antigen presentation of exogenous antigens. OBJECTIVE: The aim of this study was to evaluate whether susceptibility or resistance to asthma induced by the citrus red mite (Panonychus citri, CRM) was associated with HLA class II gene-encoded antigens. METHODS: Peripheral venous blood samples were collected from two groups of unrelated Korean adults. Ninety-one patients with citrus red mite-induced asthma and 98 exposed, healthy control subjects. The second exon of the HLA-DRB1 genes was selectively amplified by the polymerase chain reaction method. HLA typing was carried out using PCR-sequence specific oligonucleotide probes(PCR-SSOP). RESULTS: The frequency of HLA-DR7 was significantly higher among the CRM-sensitive asthmatics than among the controls (17.6% vs 4.1%, RR=3.92, p=0.01). Conversely, the frequency of HLA-DR4 was significantly lower among the CRM-sensitive asthmatics than among the controls(19.8% vs 40.8%, RR=0.36, p=0.01). No significant difference was found in the distributions of the other HLA-DRB1 gene-encoded antigens between the two groups. CONCLUSION: HLA-DRB1 genes may be involved in the development of citrus red mite-induced asthma. In addition, HLA-DR7 may increase, and DR4 decrease, the risk of developing asthma in exposed individuals.