Japanese cedar pollinosis and HLA‐DP5

Japanese cedar pollinosis is a type I allergic disease caused by Japanese cedar (Cryptomeria japonica) pollen. We investigated the association between the disease and HLA class II alleles by HLA‐DNA typing using a PCR‐SSOP method and found that the frequency of HLA‐DP5 (DPA1*02022 and DPB1*0501) was significantly increased in the patients. To investigate whether the HLA‐DP5 molecule is directly involved in the pathogenesis of the disease, Japanese cedar pollen antigen (CPAg)‐specific T cell lines were established from 3 patients who possessed HLA‐DP5 (DPA1*02022/DPB1*0501). By using these CPAg‐specific T cell lines and HLA class II‐expressing L‐cell transfectants, we found that disease‐associated HLA‐DP5 restricted T cells specific for CPAg existed in the patients. Furthermore, among 38 synthesized overlapping peptides spanning the entire length of one of the major Japanese cedar pollen allergens, Cry j 1, an immunodominant peptide which induced HLA‐DP5 restricted Th2 was identified. These observations suggest that the HLA‐DP5 may be involved, at least in part, in the pathogenesis, by helping the IgE antibody production against CPAg.