Yasuyuki Yoshizawa

The significance of complement activation in the pathogenesis of hypersensitivity pneumonitis: sequential changes of complement components and chemotactic activities in bronchoalveolar lavage fluids.

Hypersensitivity pneumonitis (HP) is believed to be induced by immunological mechanisms, the details of which remain to be clarified. While a role for cellular immunity is accepted in the pathogenesis of HP, several clinical observations also suggest a role for immune-complex-mediated lung injury. We have previously demonstrated the presence of chemotactic factors for polymorphonuclear cells (PMNs) in bronchoalveolar lavage (BAL) fluids of acutely ill patients with the summer type of HP found in Japan. The present study correlated chemotactic factors for PMNs with the level of C5a des Arg in BAL fluids obtained from patients with summer type HP. Furthermore, this study demonstrated that PMNs were increased in BAL fluids obtained after 2 days of avoidance of exposure to the presumptive causative agent. The percentage of PMNs in the BAL increased in proportion to the activity of the chemotactic factors. Finally, leukotriene B4 was not detected in concentrated BAL or supernatant fluids of cultured macrophages. These results suggest that complement activation in the respiratory tract may occur as the early event in the pathogenesis of HP.

Analysis of Bronchoalveolar Lavage Cells and Fluids in Patients with Hypersensitivity Pneumonitis: Possible Role of Chemotactic Factors in the Pathogenesis of Disease

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 breeders lung) and 4 patients at a quiescent stage (HP quiescent, 3 summer type and 1 pigeon breeders lung) were included. The results indicate that: CF for polymorphonuclear cells (PMN) in HP acute were significantly more potent than in HP quiescent; CF for mononuclear cells were not significantly different in the groups; the percentage of lymphocytes in HP acute was significantly greater even though HP quiescent revealed greater percentages of lymphocytes as compared to normal controls; 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 chemotaxis for PMN was marginally correlated with the percentage of OKT8+ cells at the acute stage of disease.

The Role of Complement-Derived Chemotactic Factors in Lung Injury Induced by Preformed Immune Complexes

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.

Accessory Cell Function of Human Alveolar Macrophages in Antigen-Induced T Lymphocyte Proliferation

We compared the accessory cell function of human alveolar macrophages (AM) to that of human blood monocytes (Mo) obtained by bronchoalveolar lavage and venipuncture from normal volunteers. Graded numbers of either AM or Mo were added to autologous peripheral blood T lymphocytes that were stimulated with a purified protein derivative of tuberculin (PPD). Either AM or Mo were cocultured with allogeneic T lymphocytes in mixed lymphocyte reaction (MLR) experiments. Both AM and Mo supported the PPD-induced T lymphocyte proliferation and allogeneic MLR at low ratios of AM or Mo to T lymphocytes with similar efficiency. However, AM showed marked suppressive effects at higher ratios of AM to T lymphocytes (1:1). PPD-pulsed AM, but not AM killed by physical treatments (heat, freeze-thaw, sonication), induced T lymphocyte proliferation. An indirect immunofluorescent study demonstrated that most AM express HLA-DR antigens. Furthermore, AM synthesized DR antigens with molecular weights of 33,000 and 29,000-31,000 daltons. When AM were treated with both anti-DR monoclonal antibody and complement, PPD-induced T lymphocyte proliferation and MLR were diminished. These results suggest that human AM function as accessory cells in the antigen-induced T lymphocyte proliferation and DR antigens on AM play an important role in the accessory cell function.

Sequential changes in lung injury induced by preformed immune complexes

Immune complexes formed in the airside may be involved in the early parenchymal changes in hypersensitivity pneumonitis. The present study was undertaken to compare the responses of animals after an intratracheal injection with preformed immune complexes to those of patients with acute hypersensitivity pneumonitis, with special emphasis on sequential bronchoalveolar lavage findings and the possible role of chemotactic factors in the immune complex-induced lung injury. An increased number and percentage of polymorphonuclear cells could be detected in bronchoalveolar lavage fluids of guinea pigs within 48 hr following an intratracheal injection of preformed immune complexes. Chemotactic factor activity preceded the observed increase of polymorphonuclear cells in bronchoalveolar lavage fluids, suggesting a role for chemotactic factors in the sequestration of these cells in the lung. In addition, this study confirmed the usefulness of bronchoalveolar lavage in evaluating the pulmonary findings because the changes in bronchoalveolar lavage cell populations correlated with sequential histological findings. The sequential characteristics of the involved areas were noted to be of a peribronchial or bronchiolar infiltration with polymorphonuclear cells at early stages, then alveolar sac infiltration, followed by mild infiltration of mononuclear cells into the alveolar walls. The findings suggest a possible role for chemotactic factors in the accumulation of polymorphonuclear cells, and the sequential changes of bronchoalveolar lavage and histological findings in animals are comparable to those in patients with acute hypersensitivity pneumonitis.

Chemotactic Factors Present in the Supernatants of Cultured Sarcoid Granulomas

The present study was undertaken to test whether cultured lymphocytes and epithelioid cells from sarcoid granulomas obtained from patients with active stage 2 sarcoidosis produced chemotactic factors (CF) for leukocytes as assessed by modified Boydens method. The results indicate that: (1) CF for mononuclear cells and for neutrophils were detected in supernatants from cultured sarcoid granulomas; (2) similar activity was detected in culture supernatants from both lymphocytes and epithelioid cells; (3) CF present in the supernatants of cultured epithelioid cells were similar physically to those which other investigators have disclosed to be released by alveolar macrophages, (4) CF in the supernatants of cultured lymphocytes were similar to the lymphokines based on an estimation of molecular size; (5) neutrophils from patients with sarcoidosis were less responsive to zymosan-activated sera and did not respond well to CF derived from their own granuloma, whereas mononuclear cells from sarcoid patients responded well to CF. In conclusion, CF are present in the supernatants of cultured sarcoid granulomas and they appear to preferentially attract mononuclear cells from sarcoid patients.