Effect of canine surfactant protein (SP‐A) on the respiratory burst of phagocytic cells

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Abstract
Cells obtained from bronchoalveolar lavage, or neutrophils of peripheral blood of dog, were incubated with the canine surfactant‐associated protein A (SP‐A). A significant decrease of the production of Superoxide anion was observed after subsequent stimulation with phorbol‐12‐myristate‐13‐acetate (PMA) as measured by the lucigenin‐dependent chemiluminesence (CL). Several other proteins used for control experiments did not decrease lucigenin‐dependent CL, indicating a specific effect of SP‐A on phagocytes. Treatment of SP‐A with collagenase prior to incubation with neutrophils destroyed the depleting effect on oxygen radical production of PMA‐stimulated cells. We propose that SP‐A acts as a regulatory factor of the respitatory burst of alveolar macrophages and neutrophils in the lungs. The inhibitory effect of SP‐A is down‐regulated by collagenase released from stimulated alveolar macrophages.