PURPOSE: In pigeon hypersensitivity pneumonitis (HP) the study of their immunological features has been helpful to explain the development of several distinctive serological and clinicopathological manifestations. The specificity of antiavian antibodies (AA) using western blot, and previous demonstration of the causative antigen in lung biopsy specimens through immunohistochemistry have supported the diagnosis in some reports. Here we used these immunological methods in order to evaluate the clinical significance and possible physiopathogenic participation of specific pigeon antigens.
METHODS: Fifty five HP patients (ATS/ERS international consensus classification) and 49 healthy asymptomatic breeders were studied. The serological profile of antiavian antibodies (AA) was evaluated through ELISA and western blot using pigeon droppings, serum, and egg yolk and white. Affinity chromatography, electroelution, and lectin binding assays were used to purify and determine the immunochemical characteristics of the main antigen targets. An immunohistochemistry using monospecific antibodies to different avian epitopes was included to study their presence in lung biopsy specimens (20 patients).
RESULTS: A 66 kDa glycoprotein was the predominant AA target using different pigeon antigens. Albumin, ovomucoid, transferrin, and IgG were the main components of this immunogenic complex. These antigens revealed a common N-glycosylation (Gal alpha 1-4Gal) pattern, and heavy chains of pigeon IgG were frequent targets of AA in HP patients (82% vs 10% in asymptomatic breeders, p=5.0-15). The immunohistochemistry was positive using antibodies raised against the 66 kDa glycoprotein and heavy chains of pigeon IgG (20 patients). A cytoplasmic staining in multinucleated giant cells and foamy macrophages were particularly found in the subacute and chronic HP groups.
CONCLUSION: The study of carbohydrate-specific AA led us to distinguish the disease from asymptomatic breeders. A heterogeneous group of foreign glycoproteins with similar immunogenic properties, including heavy chains of avian IgG may have a physiopathogenic participation since their presence in lung biopsy specimens occurred in the context of a characteristic delayed type hypersensitivity reaction.
CLINICAL IMPLICATIONS: This study describes the clinicopathological significance of an antigenic complex with a distinctive N-glycosylation pattern in pigeon hypersensitivity pneumonitis.
DISCLOSURE: Diana E. Aguilar León, No Financial Disclosure Information; No Product/Research Disclosure Information