Identification of human T cell epitopes in Japanese cypress pollen allergen, Cha o 1, elucidates the intrinsic mechanism of cross-allergenicity between Cha o 1 and Cry j 1, the major allergen of Japanese cedar pollen, at the T cell level

Summary Background Pollens from species of Cupressaceae family are one of the most important causes of respiratory allergies worldwide. In Japan, many patients with pollinosis have specific IgE to both pollens of Japanese cypress (Chamaecyparis obtusa) and Japanese cedar (Cryptomeria japonica). The sequences between Cha o 1 and Cry j 1, the major allergens of Japanese cypress and Japanese cedar pollens, respectively, are 80% identical. Objective This study was undertaken to identify T cell epitopes in Cha o 1, and to elucidate the mechanism of cross‐allergenicity between Cha o 1 and Cry j 1, at the T cell level. Methods T cell epitopes in Cha o 1 were identified by the reactivity of T cell lines, generated from 19 patients, to stimulation with overlapping peptides. The subsets of T cell clones specific to rCha o 1 were determined according to their ability to produce IL‐4 and IFN‐γ. Peptide specificities of two T cell clones were determined by stimulation with the peptides from Cha o 1 and Cry j 1. Results Four dominant and six subdominant T cell epitopes were identified in Cha o 1. While four T cell epitopes, p11‐30, p211‐230, p251‐270 and p331‐350, were common to Cha o 1 and Cry j 1, 4 T cell epitopes, p61‐80, p71‐90, p311‐330 and p321‐340, were considered to be unique to Cha o 1. The subsets of T cell clones were predominantly of T helper2‐type. One T cell clone recognized p16‐30, which is common to Cha o 1 and Cry j 1, but another recognized p321‐330, which is unique to Cha o 1. Conclusion Presence of both T cells reactive to T cell epitopes common to Cha o 1 and Cry j 1 and T cells specific to T cell epitopes unique to Cha o 1 in patients with pollinosis contributes to prolonged symptoms after the cedar pollen season in March and the following cypress pollen season in April.