Pathogenesis of summer-type hypersensitivity pneumonitis : Analysis with serotype-related polysaccharide of Trichosporon cutaneum and its nonoclonal antibodies

夏季型过敏性肺炎（SHP）是一种独特的过敏性肺炎，在日本最常见。我们以前的研究阐明，该疾病的病原体是皮肤丝孢酵母，并且SHP患者具有高滴度的针对多糖性质的酵母型特异性抗原的抗体，该抗原存在于酵母培养上清液的高分子量部分中。本研究利用抗血清II型皮肤毛癣菌单克隆抗体D-8，通过凝胶过滤和亲和层析纯化了血清II型皮肤毛癣菌的血清型特异性抗原，并对其结构进行了鉴定。亲和纯化的抗原显示为基本上酸性多糖，其包含甘露糖、木糖和葡糖醛酸。化学分析表明，该多糖抗原含有（1-3）-连接的甘露聚糖主链，主链上连接有（1-4）-连接的甘露糖短链和一小部分（1-2）-连接的木糖残基，通过取代主链的（1-3）-连接的甘露糖残基的2-或4-位。免疫扩散试验和夹心酶联免疫吸附试验使用单克隆抗体D-8显示的抗原表位涉及的末端葡萄糖醛酸残基。

Summer-type hypersensitivity pneumonitis (SHP) is a unique type of hypersensitivity pneumonitis and the most prevalent in Japan. Our previous study clarified that the causative agent of the disease is Trichosporon cutaneum, and that the patients with SHP have high titer of antibodies against the serotype-specific antigen of polysaccharide nature which exist in the high molecular weight fraction of the culture supernatant of the yeast. In this study, we purified the serotype-specific antigen of serotype II T.cutaneum by gel filtration and affinity chromatography using a monoclonal antibody, D-8, specific for serotype II T.cutaneum, and elucidated the structure of the antigen. The affinity-purified antigen was shown to be essentially acidic polysaccharide comprising mannose, xylose, and glucuronic acid. Chemical analysis showed that this polysaccharide antigen contains a (1-3)-linked mannan backbone attached with short chains of (1-4)-linked mannose and a small portion of (1-2) linked xylose residues by substituting the 2-or4- positions of the (1-3)-linked mannose residues of the main chain. The antigenic epitope was shown to involve the terminal glucuronic acid residues as revealed by immunodiffusion test and sandwich enzyme-linked immunosorbent assay using monoclonal antibody D-8.