B-lymphocyte aggregates in alveoli from a child with hypersensitivity pneumonitis (bird breeders lung)

Background: Hypersensitivity pneumonitis is an interstitial lung disease me diated through a patient's immunologic response to a variety of inhaled org anic dusts. Studies of the cellular components of lavage fluid from patient s with this disease show marked increases of CD8(+) suppressor/cytotoxic T- lymphocytes. Objective: In this study, we identified, in addition to the expected suppre ssor T-cells and natural killer cells, follicle-like aggregates of B-cells in the lung interstitium of an affected patient. Methods: The patient was an 11-year-old non-asthmatic, Caucasian male who p resented with a 4-month history of progressive dyspnea, cough, and fever. T he home contained nine cockatiel and two doves. Admission pulmonary functio ns revealed a restrictive pattern with diminished diffusion capacity. Prior to a diagnosis, the patient underwent bronchoalveolar lavage and transbron chial biopsy. Serum precipitins were eventually positive to pigeon (which c ross-reacts with drove) droppings. The symptoms resolved after a prolonged course of prednisone. Results: Analysis of bronchoalveolar lavage lymphocyte population revealed a predominance of CD8(+) cells (50%) with 85% expressing the activation mar ker HLA-DR. The percentage of CD4(+) and CD56(+) were 32% and 16%, respecti vely. The transbronchial biopsy revealed CD20(+) follicle-like aggregates w ithin the lung interstitium. Conclusions: The histopathologic findings confirm that in hypersensitivity pneumonitis, the predominant immune response is an infiltrate of CD8(+) T c ells. The presence of B cell aggregates, however, may indicate that the loc al synthesis of antibody may be involved in an antibody-dependent cellular cytotoxic mechanism.