The current study concerns immunological mechanisms involved in the pathogenesis of hypersensitivity pneumonitis (HP) by an analysis of the cells and chemotactic factors (CF) obtained by bronchoalveolar lavage (BAL). Nine patients at an acute stage (HP acute, 8 summer type and 1 pigeon breeder’s lung) and 4 patients at a quiescent stage (HP quiescent, 3 summer type and 1 pigeon breeder’s lung) were included. The results indicate that: (1) CF for polymorphonuclear cells (PMN) in HP acute were significantly more potent than in HP quiescent; (2) CF for mononuclear cells were not significantly different in the groups; (3) the percentage of lymphocytes in HP acute was significantly greater even though HP quiescent revealed greater percentages of lymphocytes as compared to normal controls; (4) determination of T cell subsets employing OKT antibodies revealed the ratio of OKT8⁺ cells to OKT4⁺ cells in HP acute was significantly higher than in HP quiescent, and (5) chemotaxis for PMN was marginally correlated with the percentage of OKT8⁺ cells at the acute stage of disease.

Our previous studies have suggested a role for complement fragments presumably activated by immune complexes in patients with hypersensitivity pneumonitis. The present study has shown that circulating complement depletion by cobra venom factor resulted in the reduction in severity of immune-complex-mediated pulmonary inflammation. The activity of chemotactic factors for neutrophils generated in bronchoalveolar lavage fluids in complement-depleted animals was significantly diminished to 61.2% compared to the undepleted animals. In addition, reduced activity of chemotactic factors resulted in a marked reduction of accumulation of neutrophils in bronchoalveolar lavage fluids indicating that chemotactic factors play an important role in the sequestration of neutrophils on the alveolar side of the lung. In conclusion, chemotactic factors in bronchoalveolar lavage fluids which preceded the accumulation of polymorphonuclear cells are partially derived from complement.

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High incidences of MS were observed in this particular pathology. An extremely narrowed true lumen was accompanied by a high incidence of MS and mortality.

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