QUANTIFYING PHAGOCYTOSIS OF MYCOBACTERIUM-AVIUM COMPLEX BY HUMAN MONOCYTES IN WHOLE-BLOOD

Studies of phagocytic efficiency in cells of the macrophage lineage ha ve assumed additional importance since the discovery that HIV infectio n of these cells impairs their immune function. A rapid method has bee n developed for measuring phagocytosis of the opportunistic pathogen M ycobacterium avium complex by human monocytes. Fluoresceinated M. aviu m complex (F-MAC) was incubated with whole blood at 37 degrees C and t he fluorescence of extracellular F-MAC was quenched using a vital blue stain. Monocytes were then stained with a monoclonal antibody (mAb) t o human CD14 conjugated to phycoerythrin (PE) red cells were lysed, an d the percentage of monocytes which had phagocytosed F-MAC was measure d by flow cytometry. The results were reproducible in samples of blood taken from individual donors over a period of 1 or 2 weeks, and optim um F-MAC concentrations and an optimum incubation time were determined by experiment. This method has the advantages of requiring only a sma ll volume of blood, not necessitating manipulation of cells before tes ting, and using a phagocytic target relevant to the pathogenesis of HI V infection.