Enhancement of neutrophil-mediated phagocytosis by human granulocyte-macrophage colony-stimulating factor demonstrated using a novel mathematical model.

A mathematical model is presented which may be applied to describe and analyse data from microscopic phagocytosis assays. The method has been used to investigate the phagocytosis of opsonized yeast by peripheral blood neutrophils treated with purified recombinant human granulocyte-macrophage colony-stimulating factor (rH GM-CSF) in vitro. Under limiting conditions of serum opsonization, rH GM-CSF decreased the proportion of non-phagocytic cells and increased the mean number of ingested yeast per cell. Stimulation of phagocytosis was dose-dependent and occurred with concentrations of rH GM-CSF in the range 10-320 units/ml. The effect was dependent on a heat-labile component in serum and was not attributable to endotoxin contamination of the preparation.