Membrane expression of Fc-receptors in cultured leukemic cell lines. I. Induction of Fc-receptor in undifferentiated types of cells after passive modulation of lipid viscosity.

The role of lipid environment of plasma membrane for the expression of Fc receptor (gamma) (FcR gamma) were studied by physicochemical modification of the membranes of myeloid leukemia cell line cells, M1. Sterol binding polyene antibiotics such as amphotericine B or filipin inhibit the expression of FcR gamma during the differentiation of M1- cells by the CM obtained from the culture of mouse embryonic fibroblasts, suggesting the possible involvement of cholesterol molecules in the induction mechanism of FcR gamma. Low-temperature incubation at either 20 degrees C or 4 degrees C results in the increment of their membrane microviscosity, when tested by the fluorescence depolarization method, in company with the appearance of FcR gamma on approximately 60% of M1 cells when assayed by the EA-rosetting method. FcR gamma is also induced on approximately 40% of M1- cells by incubating cells with cholesterol-phosphatidyl-choline liposomes with the concomitant increase of their membrane microviscosity. Nevertheless, no phagocytosis of EA is observed in these cells treated with such physicochemical procedures. These findings imply that FcR gamma is embedded in the membrane of M1- cells and that physicochemical modification of the membrane lipid bilayers can induce the FcR gamma independent on their functional differentiation marked by the expression of phagocytic activity.