Flow cytometric studies on phagocyte function in bacterial infections.

Polymorphonuclear neutrophilic leukocyte (PMNL) phagocytosis of fluorescein-isothiocyanate labelled Staphylococcus aureus was studied by flow cytometry (FCM) in 41 patients with bacterial infections. Practically all phagocytic cells (granulocytes and monocytes) showed active uptake of fluorescent bacteria. However, the mean fluorescence of the phagocytes was about 15% lower than that of cells from healthy volunteers. This reduction was only seen in the male patients, not in the females. The fluorescence reduction was related neither to the type of infectious agent (Gram-positive versus Gram-negative) nor to the white blood cell count or percentage of immature leukocytes. Five patients with cured infections had phagocyte fluorescence similar to that of the controls. In two patients, phagocyte fluorescence was very low, indicating reduced phagocytosis. Phagocyte fluorescence was not related to patient survival.