Morphological studies of peripheral monocytes during in vitro maturation by scanning electron microscopy

Human peripheral monocytes were cultured in autologous serum over a period of 14 days. Morphological changes were observed in both light and scanning electron microscopy. Nonspecific esterase, Fc receptor, and phagocytic activities were studied using antibody-coated sheep erythrocytes. Though the spreading of cytoplasm was observable in a light microscope, scanning electron microscopic pictures revealed several interesting changes during the culture period. The number of filopodia and microvilli increased as the duration in cultured increased. At the end of 7 days, almost pure monocytes remained in culture. These cells were characteristically 98-100% nonspecific-esterase positive, Fc-receptor positive, and highly phagocytic. This technique may be of value in understanding changes due to various specific and nonspecific immune stimulators.