Bestatin-induced enhancement of in vivo phagocytosis determined by a new simple assay.

Pretreatment of mice by the immunostimulator bestatin resulted after four days in a significant enhancement of the phagocytic activity of peritoneal cells. For quantification of the phagocytic process of murine peritoneal phagocytes a new in vivo assay is proposed. Fluorescein isothiocyanate (FITC)-labeled Escherichia coli bacteria were i.p. injected. After ten minutes peritoneal cells were harvested and the phagocytic index of peritoneal phagocytes was fluorescence-photometrically assessed. The frequency distribution of phagocytized bacteria per cell found by the this assay corresponded to Poisson distribution. This coincidence allowed estimation of the minimum number of cells needed for detecting a significant difference of phagocytosis indices, resulting in an enhancement of test efficiency.