A method for simultaneous determination of rosette formation and phagocytosis by cells.

A fluorescent agent insoluble in water was readily phagocytosed by 5-20% of human blood mononuclear cells, mainly monocytes. These cells were easily detected even amidst abundant rosetting erythrocytes. When rosette assays for the detection of complement or SRBC receptors on the surface of the cells were performed, only phagocytic cells exhibited the complement receptor with the method used in the study, whereas mainly nonphagocytic cells formed SRBC rosettes. The effect on the calculation of the percentage of T lymphocytes (SRBC receptor lymphocytes) of varying amounts of monocytes present in mononuclear cell population is demonstrated. The method presented here might prove useful particularly in studies on Fc or complement receptors on white blood cells.