PURPOSE: Pigeon hypersensitivity pneumonitis (HP) is a lung disease caused by the inhalation of organic antigens of bird origin. Specific antibodies, a positive cellular reactivity, or antigen challenge tests have been useful to approach the etiological diagnosis. Since lung biopsy has not disclosed pathognomonic findings, and the exposure to airborne dusts may explain the histopathologic manifestations, we studied whether the presence of pigeon antigen by immunohistochemistry may define the cause of the disease.
METHODS: Twelve pigeon HP patients were studied. The diagnostic procedures included the determination of antiavian antibodies, pulmonary function tests, and imaging studies by roentgenograms and/or HRCT. A surgical lung biopsy was performed as part of the disease evaluation. For the immunohistological detection of the causative antigen, a rabbit polyclonal antibody was raised against high and low molecular antigens of pigeon serum (patent pending), and its specificity was confirmed by western blot using secondary biotinylated antibodies and streptoavidin-peroxidase (Vector, USA.).
RESULTS: A variable histopathological spectrum was found in pigeon HP. All patients showed interstitial infiltration constituted by lymphocytes, plasma cells and macrophages. Multinucleated giant cells (MCG) were also frequent (83%), and the granulomatous reaction was a less common finding (25%). The immunohistochemistry revealed a predominant cytoplasmic immunostaining in MCG, histiocytes, and foamy macrophages showing a different distribution that ranged from inconspicuous clusters of cells to well formed granulomas. This method revealed negative results using lung biopsies from patients with usual interstitial pneumonia, and lung fibrosis secondary to scleroderma.
CONCLUSION: Different immunologic tests have been used to evaluate the cause of HP. In this study we demonstrate the presence of pigeon antigen in the lung by immunohistochemistry. This method was a helpful alternative to confirm the diagnosis of pigeon HP, and may provide the possibility to differentiate it from other respiratory conditions. In addition, our findings support that some histopathological features of the disease, particularly the formation of MGC are the result of a specific antigen exposure.
CLINICAL IMPLICATIONS: This study deals with a new diagnostic method in pigeon HP.
DISCLOSURE: Erasmo Martínez-Cordero, No Financial Disclosure Information; No Product/Research Disclosure Information