Flow cytometric analysis of the functional ability of neutrophils from patients with autoimmune neutropenia

Flow cytometry has been used to evaluate the functional ability of neutrophils and the expression of IgG Fc receptors (FcRII and FcRIII) in autoimmune neutropenia. Quantification of the neutrophil oxidative burst was made by assaying the production of 2'7'-dichlorofluorescein (DCF) from non-fluorescent 2'7'-dichlorofluorescein trapped within the cell, by flow cytometric analysis of cellular fluorescence. In the present study the DCF assay was used to examine the response of neutrophils to stimulation by opsonized and non-opsonized Staphylococcus aureus. In addition, the rate of uptake of S. aureus labelled with the red nuclear dye propidium iodide was determined. The presence of surface-bound immunoglobulin, which may affect the phagocytic capacity of the neutrophil, was also measured. No correlation between the neutrophil count and level of membrane-bound IgG or the rate of bacterial uptake was found. The studies were performed on twenty patients with autoimmune neutropenia, twelve with other autoimmune disorders and fourteen normal controls. The rate of uptake of bacteria was considered in relation to the expression of FcRII and FcRIII. Good correlation was found with the level of expression of FcRII, the major receptor for neutrophil activation, and the rate of uptake of bacteria (r = 0.64).