Phagocytic ability is induced by ATRA differentiation.

Abstract

<p>A. Effect of opsonization on interaction. Differentiated HL-60 cells were allowed to interact at 37°C with Oregon Green-labeled BMJ71 bacteria, either IgG-opsonized (1 mg/ml) or not, at a bacteria/cell ratio of 10∶1. After a synchronized presentation, the samples were incubated at 37°C as indicated. Analysis was by flow cytometry. An interaction ratio was calculated by dividing the number of cells interacting with Oregon Green-labeled bacteria with the total number of cells. Error bars show SEM, based on a total of three experiments; *  = p<0.05. B–C. Interaction and internalization during differentiation. The ability of HL-60 cells to associate with and to internalize BMJ71 bacteria was measured. Oregon Green-labeled and IgG-opsonized bacteria were allowed to interact for 5 min with the cells at a bacteria/cell ratio of 2∶1. Analysis was by fluorescence microscopy. Error bars represent SEM of two separate experiments. D. Phagocytic ability induced by ATRA-treatment. Fold increase of phagocytic ability arrived at by normalizing the phagocytic ability of ATRA-treated cells to the corresponding control sample. E. Basis for calculations. The different formulas used for the analysis of data in the figures B–D are presented. Interaction is defined as the fraction of all cells that are associated with at least one bacterium. Interacting cells were further analyzed to determine how large a fraction of the associated bacteria was intracellular. The term phagocytic ability was constructed to take interaction as well as internalization into account.</p