Twenty-one different biotinylated lectins were used to recognize the carbohydrates of Aspergillus umbrosus, one of the most common microbes that patients with farmer's lung in Finland are exposed to. The glycoprotein fraction of A. umbrosus was bound especially well by Concanavalin A and consisted mainly of carbohydrates mannose and glucose. The carbohydrate fraction of A. umbrosus antigens were isolated from the crude extract of A. umbrosus with Con A-Sepharose affinity chromatography. Serum IgG antibodies to A. umbrosus mannoprotein fraction were determined in 57 patients with farmer's lung, 10 asymptomatic exposed farmers and 10 healthy controls by enzyme linked immunosorbent assay. Candida albicans and Saccharomyces cerevisiae mannan were used as controls. Patients had high levels, whereas asymptomatic exposed farmers showed moderate, and health controls low levels, of IgG antibodies to the A. umbrosus mannan/mannoprotein fraction. There were no significant differences in the mean antibody levels between the patients and controls against C. albicans or S. cerevisiae mannose fraction although in all groups more antibodies were detected against C. albicans than S. cerevisiae.

Fifty patients with farmer's lung disease (FL), 20 asymptomatic exposed farmers, and 18 healthy controls were investigated for total IgG and total IgA, as well as subclass antibody levels against Aspergillus umbrosus, the most common fungus to which FL patients in Finland have been exposed. Enzyme-linked immunosorbent assay (ELISA) revealed significantly elevated levels of specific total IgG and IgA antibodies in the sera of patients during the acute phase of the disease. Both IgG1 and IgG2 subclass antibodies and both IgA1 and IgA2 subclass antibodies were significantly associated with the disease. The antibody levels decreased during the first 3 months, when mould exposure was avoided and when an oral 6-week steroid treatment was administered. During the next 12 month follow-up, the mean antibody levels continued to decrease, even though re-exposure might have occurred. The results (with sensitivity 94% and specificity 95%) imply that in addition to the measurement of A. umbrosus-specific IgG, determination of both A. umbrosus-specific IgG1 and IgA might also be useful in the serodiagnosis of acute stage of FL.

SUMMARYFarmer's lung disease (FL)-the commonest form of allergic alveolitis caused by repeated inhalation of mouldy hay. is associated with exposure lo the fungus Aspergithis umbrosus among Einnish farmers. The antigen-binding avidity of A. j/mA/asM.s-specific IgG antibodies was measured in 12 EL patients in acute phases of initial and recurrent attacks and during 1 year foliow up as well as in 12 healthy farmers and five healthy urban controls. The farmers* groups were further divided into two subgroups: subjects with short exposure ( < 7 years) and subjects with long exposure (> 25 years). During the first acute phase PL patients with long exposure exhibited a high avidity of /I, umbrosusspecifie IgG antibodies that remained high during the I year follow up, although tlie A. umbrosusspecific IgG antibody tilre decreased. A re-exposure lo mouldy hay leading to a recurrence further enhanced ihc maturation ofthe antibody avidity, so thai an even higher A. um6r05«s-specific IgG avidity with a less signiticant increase of antibody tilre occurred than during the first acute attack. Notably higher IgG anlibody avidity was observed in FL patients with long exposure than in healthy farmers or in healthy controls.

IgG and IgA antibodies against fungus Aspergillus umbrosus have been found in the sera of patients with farmer’s lung (FL) disease and healthy exposed farmers in Finland. To determine the IgE response to antigens of A. umbrosus and Candida albicans, sera from 20 patients with FL, 20 healthy farmers and 20 nonfarming controls were tested by nitrocellulose radioallergosorbent test (RAST). The values of RAST indices were low in each group and the only statistically significant difference was found between the groups of FL patients and nonfarming controls against A.umbrosus polysaccharide antigen. Individual IgE responses to polysaccharide antigens of A. umbrosus and C. albicans correlated among FL patients, however, no cross-reacting IgE antibodies could be shown. To conclude, the IgE antibody levels of A. umbrosus polysaccharide and crude antigens were low in FL patients, healthy exposed farmers and nonfarming controls. Neither polysaccharide nor crude antigen-specific IgE antibodies of A. umbrosus have any diagnostic value in FL disease.

Gold-and FITC -conjugated antibodies were distributed mostly on the outer wall layers of conidia, hyphae and phialides of Aspergillus umbrosus and GlcNAc beta 1-linked lectins had the strongest affinity to the outer wall layers.