Mucosal immunity in extrinsic allergic alveolitis: salivary immunoglobulins and antibody against inhaled avian antigens among pigeon breeders

Background Inhaled antigens from pigeons can cause extrinsic allergic alveo litis (EAA); a model disease of pulmonary inflammation Among pigeon breeder s, serum antibody and sensitized lymphocytes specific for these antigens ha ve been described primarily, but not always, with disease. Antibody activit y within the lung may have a closer association with disease, however, samp ling by alveolar lavage at bronchoscopy is impractical for screening, there fore we used saliva to quantify the mucosal antibody response. Objective To establish: (a) if antibody activity against inhaled avian anti gens was detectable in the saliva of pigeon breeders, (b) if the distributi on of saliva antibody and total immunoglobulin levels were quantitatively o r qualitatively different from serum, and (c) whether the hypersensitivity symptoms of EAA were associated more with the mucosal or the systemic humor al immune response. Measures Saliva and serum total and avian antigen-specific IgG, IgA (IgA1 a nd IgA2) antibody activity in 87 pigeon breeders and 24 control subjects wi th no avian exposure. Albumin levels were used as a protein reference and c otinine levels confirmed smoking status. Specific hypersensitivity symptoms and various exposure indices to pigeons were established by interview. Results Absolute levels and relative proportions (vs albumin) of IgG, IgA a nd IgA1 in saliva, and IgG in serum, were significantly higher in pigeon br eeders compared with controls, suggesting mucosal inflammation Avian antige n-specific antibody of all isotypes was readily demonstrable in saliva (pre dominantly IgA) and serum (predominantly IgG) from pigeon breeders, and the re were no significant titres in controls. The levels of IgG antibody in sa liva and in serum correlated significantly (r=0.52, P<0.001), and both corr elated with the raised immunoglobulin levels. In both saliva and serum the IgG rather than the IgA antibody activity was associated with symptoms of E AA. Conclusions Antibody activity in saliva and serum, representing the mucosal and systemic responses, respectively, were both strongly stimulated by inh aled antigens. The IgG antibody titres of saliva and serum correlated signi ficantly and were a useful index of inflammation, as measured by the raised total immunoglobulin levels, and symptoms. This suggests that IgG antibody in serum may reflect clinical and immunological sensitization of the lung mucosa. Collecting saliva is noninvasive, and saliva antibody measurement i s a convenient method for monitoring EAA, especially in children, and will facilitate sampling for example in epidemiological studies of antibody prev alence.