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Neutrophil activation results in neutrophil adherence and may subsequently cause lung injury through the generation of oxidants, release of granule proteases, and generation of a variety of mediator substances. We hypothesized that inhibition of neutrophil adherence and subsequent lung sequestration would attenuate the lung injury caused by activated neutrophils. Using isolated perfused rat lungs, we determined if anti-Mo1 monoclonal antibody (binds to the alpha subunit of a neutrophil glycoprotein [gp 155.94] that facilitates adherence) would attenuate lung neutrophil sequestration and lung injury caused by human neutrophils stimulated by phorbol myristate acetate (PMA). PMA- stimulated neutrophils but not PMA or neutrophils alone caused lung injury as assessed by accumulation of 125I-bovine serum albumin into lung parenchyma and alveolar lavage fluid. Incubation of neutrophils with anti-Mo1 antibody prior to stimulation with PMA attenuated lung injury and neutrophil sequestration. Furthermore, a histological survey revealed that anti-Mo1 antibody inhibited neutrophils present in the lung from spreading following exposure to PMA. Anti-Mo1 antibody did not inhibit PMA-stimulated neutrophil release of granule constituents or toxic O2 metabolites as evidenced by lysozyme and lactoferrin release or the reduction of ferricytochrome c in the lung perfusate. The inhibition of lung injury caused by the anti-Mo1 antibody was not likely due to a nonspecific effect of the antibody, since another murine monoclonal antibody of the same class (anti-Mo5) did not inhibit lung neutrophil sequestration or lung injury. Thus, in this experimental model, interference with the close approximation of the neutrophil to its target site inhibited the ability of the activated human neutrophil to cause injury.

During phagocytosis of opsonized lipopolysaccharide-coated paraffin oil droplets, rabbit alveolar macrophages reduced nitroblue tetrazolium, which effect was in part inhibitable with the use of superoxide dismutase. Exposure of cytochalasin-B-treated rabbit alveolar macrophages to opsonized zymosan led to the generation of superoxide, as quantitated by ferricytochrome C reduction. It was found that nitroblue tetrazolium in the presence of ferricytochrome C could in turn serve as scavenger of superoxide during stimulation of cytochalasin-B-treated rabbit alveolar macrophages. Following challenge with either opsonized zymosan or the membrane perturbant digitonin, rabbit alveolar macrophages released hydrogen peroxide into the extracellular medium. Employment of the surface membrane stimulant phorbol myristrate acetate led to activation of the hexose monophosphate shunt, which activity could be further enhanced in the presence of superoxide dismutase or attenuated in the presence of catalase. These studies demonstrate that rabbit alveolar macrophages release superoxide and hydrogen peroxide during surface membrane perturbation. In turn, hydrogen peroxide generation can stimulate the hexose monophosphate shunt.