Epitope analysis of birch pollen allergen in Japanese subjects.

Birch pollen is a very common cause of nasal allergy (pollinosis) not only in Scandinavia, Europe, Canada, and the northern part of the United States but also in Hokkaido, Japan. We have previously reported a positive association between the HLA-DR9 phenotype and the development of birch pollen allergy in Japanese subjects. However, there is little information about T cell epitopes of birch pollen which are presented by HLA class II molecules other than HLA-DR9. Therefore, we analyzed the difference in T cell epitope usage in patients who had HLA-DR9 versus those who did not. Seven Japanese patients with birch pollinosis were studied. Some groups of peptides representing T cell epitopes (Betula verrucosa; Bet VI peptides, p7-33, p23-46, p138-160) appeared to be shared by the majority, while another peptide (Bet VI p72-95) was recognized predominantly by patients who expressed HLA-DR9 and/or HLA-DQ3 molecules. Moreover, seven T cell clones and eight T cell lines were generated from two patients who did not have HLA-DR9 or HLA-DQ3. Using some of these T cell clones/lines, we investigated the relationship between HLA class II molecules and antigenic peptides. One of these T cell clones recognized antigenic peptides in the context of the HLA-DQ1 molecule. To our knowledge, this is the first indication that the epitope on Bet VI can be presented by the HLA-DQ molecule.