RESUMO
The association of rheumatoid factor (RF) and lung disease in several immunologically mediated conditions has suggested that it may be physiopathologically relevant. Since previous reports in hypersensitivity pneumonitis (HP) have dealt mainly with the immunoglobulin M (IgM) RF measurement, we studied such antibody activity in other immunoglobulins, to determine the IgG and IgA RF levels in pigeon-HP, and in asymptomatic breeders (AB) and rheumatoid arthritis (RA) as controls. RFs were measured in 35 HP patients, 41 AB, 31 RA controls, and 55 healthy donors by enzyme-linked immunosorbent assay (ELISA) using human or rabbit immunoglobulin G (IgG), anti-IgM, F(ab')2 of IgG, and IgA F(ab')2 conjugates. An affinity chromatography, fragment crystallizable (Fc) preparations of IgG, pepsin digestion, and Western blots were used to confirm RF specificity. We also evaluated anti-avian antibodies (AA) and cross-reacting antibodies. The HP group revealed positive IgM (51.4%), IgG (31.4%), and immunoglobulin A (IgA) (34.2%) RF tests, and these antibody values exceeded the AB reference levels (P<0.02). HP and RA showed a similar frequency and distribution of RFs. Possible immunoassay interferences were excluded. As in other immunologically mediated diseases, IgG and IgA RFs may play a pathogenic role in HP, amplifying the inflammatory reaction, immune-complex formation, and complement activation. IgM-RF producing cells that have been implicated in the presentation of self and foreign antigens, and T-cell activation might induce the isotype switching of RFs.
Assuntos
Pulmão do Criador de Aves/imunologia , Imunoglobulina A/imunologia , Imunoglobulina G/imunologia , Imunoglobulina M/imunologia , Fator Reumatoide/sangue , Adulto , Pulmão do Criador de Aves/sangue , Feminino , Humanos , Masculino , Fator Reumatoide/classificaçãoRESUMO
A number of clinicopathological manifestations may define the presence of hypersensitivity pneumonitis. Histological study is used to establish the diagnosis and to differentiate the disease from other respiratory disorders. This case report suggests that immunohistological demonstration of the causative antigen in the lung may be a useful diagnostic approach in cases of pigeon hypersensitivity pneumonitis. A 52 year-old woman was studied. She had a prior history of pigeon exposure, and lived in an area with a high prevalence of tuberculosis. Her clinical presentation, respiratory function tests and imaging studies revealed a predominant interstitial lung disease. The results of antiavian antibodies, bronchoalveolar analysis, and other laboratory parameters were non-diagnostic. A lung biopsy showed a prominent granulomatous reaction with a sarcoid-like appearance in some areas, and an interstitial infiltration constituted by lymphocytes, plasma cells and foamy macrophages. Although the disease manifestations were compatible with hypersensitivity pneumonitis, we decided to study the causal antigen by immunohistochemistry. The use of a polyclonal antibody raised against pigeon serum showed a predominant cytoplasmic immunostaining in multinucleated giant cells and histiocytes from lung granulomas. Other respiratory disorders were reasonably excluded. Previous exposure to a known antigen may support the diagnosis of hypersensitivity pneumonitis. Although the inhalation of organic dusts may be clinically evident, the aetiology is commonly evaluated by different challenge tests or immunological methods. We propose that the study of pigeon antigen by immunohistochemistry may be used as part of the diagnostic approach for hypersensitivity pneumonitis.