| Research Abstract |
To investigate the immunopathogenesis of Japanese summer-type hypersensitivity pneumonitis (SHP), we evaluated the immunopathogenic properties of Trichosporon cutaneum, a major causative agent of the disease. When the culture filtrate antigen of T. cutaneum was chromatographed on DEAE-cellulose, two peaks of polysaccharide, fraction A and B, were obtained. Fraction B was highly reactive to the specific IgG and IgA antibodies in the serum and bronchiol alveolar fluid samples obtained from sensitized rabbits, where fraction A was mainly reactive to the IgG antibodies. When the rabbits sensitized by the intratracheal injection with the particulate anten of T. cutaneum were challenged intratracheally by these antigenic fractions, fraction B induced granulomatous alveolitis, but fraction A induced alveolitis rather than granuloma. Lymphocytes of the mediastinal lymph node responded prominently to fraction B, but less to fraction A, as assessed by proliferative response. Each of the fraction
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s B obtained from two strains of different serotypes was reactive in enzyme-linked immunosorbent assay to the serum samples from the rabbits sensitized with homologous antigen, but far less to that from the rabbits sensitized with heterologous antigen, that is, the antigenic specificity of fraction B was related to the serotype of T. cutaneum. Fraction by gel filtration on Sepharose CL-4B revealed that the molecular weight of the antigenic components in fraction B was larger than 1,000,000 and that the components consisted mainly of polysaccharide. In immunodiffusion, the high molecular weight fractions of serotypes I and II showed precipitin lines reacting with each of the homologous antisera, but no line with the heterologous antisera. This antigenic activity was sodium-perodate-sensitive and pronase insensitive, suggesting a polysaccharide nature. Inhalation challenge test with the serotype-related polysaccharide antigen resulted in positive in SHP patients, but not in exposed asymptomatic family members. Less
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