Neutrophils in normal lungs.

Abstract

This report reviews the role of the lungs in the normal metabolism of neutrophils and the putative role of the neutrophil in lung metabolism. There are many apparent connections between the peripheral supply of neutrophils and the lungs. Neutrophils develop from primitive precursor cells in the bone marrow. Human alveolar macrophages secrete a factor that stimulates these precursors to proliferate. The neutrophils leave the marrow at carefully controlled rates to keep the concentration of peripheral neutrophils constant. Once the cells enter the circulation, they are rapidly distributed between the marginated and circulating pools. Together these pools comprise the total blood neutrophil pool. A large part of the marginated pool occurs in the lungs. Some agents that cause widespread sequestration of neutrophils in the lung capillaries may cause endothelial cell damage; however, normally the neutrophils leave the circulation relatively rapidly, with half lives from 3.5 to 7 h in different species. Inflamma...