Oxidative metabolism of pulmonary phagocytes in acute pneumonia

The oxidative response of activated phagocytes is a primary host defense mechanism in pneumonia, but is in addition capable of causing tissue damage. We evaluated amount and significance of the local oxidant production in immunocompetent and immunocompromised pneumonia patients; the relative contribution of neutrophils and alveolar macrophages to the total oxidant load was differentiated using chemiluminescence (CL) with different amplifiers. Luminol-enhanced CL correlated to neutrophil percentage and myeloperoxidase levels in the bronchoalveolar lavage and was markedly increased in both pneumonia groups. Lucigenin-enhanced CL was produced by both phagocyte types and not significantly increased. In both pneumonia groups elevated levels of serum proteins indicated severe alveolocapillary leakage. In conclusion the oxidative response in acute pneumonia was mainly due to neutrophil recruitment and activation; this defense mechanism was preserved even in severely immunocompromised patients.