Immunological studies of the glycoprotein allergen Ag-54 (Cla h II) in Cladosporium herbarum with special attention to the carbohydrate and protein moieties

The glycoprotein allergen Ag-54 (Cla h II) isolated from Cladosporium herbarum was split into its carbohydrate and protein moieties by using alkaline-borohydride treatment and deglycosylation, respectively. The native Ag-54, the deglycosylated protein and the protein-free carbohydrate moieties were tested for IgE-binding activity by radioallergosorbent test inhibition using selected sera from individuals with C. herbarum allergy. The deglycosylated material had a stronger allergenic activity than the native Ag-54 with all the sera tested. The Ag-54 carbohydrate moieties were not found to possess any IgE-binding activity. The galactoglucomannan part of the carbohydrate moiety was isolated and it was demonstrated to precipitate IgG rabbit antibody. Removal of the galactofuranose units by mild acid hydrolysis did not alter the IgG-binding capacity of the polysaccharide, indicating that galactofuranose was not immunodominant.