Circulating CD35−/CD49d+ neutrophils in influenza virus infection patients

Release of immature neutrophils from bone marrow into circulation accompanies acute inflammatory states. Previous studies have identified a number of antigens that are differentially expressed on mature neutrophils and immature forms. We analyzed expression of these antigens on circulating neutrophils of influenza virus infection patients. We identified a minor neutrophil subpopulation with decreased granularity and the antigen surface expression pattern (CD35−/CD49d+) which defines metamyelocytes. CD35−/CD49d+ neutrophils were detected in 35% of the patients but not in healthy individuals and correlated positively with blood metamyelocyte count. The sorted CD35−/CD49d+ neutrophils displayed morphological features of metamyelocytes. Compared with a major (CD35+/CD49d−) neutrophil subpopulation, CD35−/CD49d+ neutrophils demonstrated significantly diminished functional capacities (both phagocytosis and respiratory burst). Thus, CD35−/CD49d+ neutrophils represent a phenotypically and functionally distinct subpopulation of the cells and can potentially be used to quantify immature neutrophil release in inflammation.