Table 3.

Cupping Is Not Inhibited by Cytochalasin D in COS Cells

COS transfectant		Cytochalasin D +/−		Distribution of beads by location: % of total						Total No. of beads associated with cells
				Surface		Cupped		Sealed
FcγRIA		−		36		63		1.5		80
FcγRIA		+		46		54		0		95
FcγRIA + γ chain		−		11		59		30		148
FcγRIA + γ chain		+		35		62		3		107
FcγRIIA		−		76		4		20		25
FcγRIIA		+		83		17		0		53

COS transfectants were incubated with IgG-coated latex beads with or without 1 μg/ml Cytochalasin D at 37°C for 1 h. Cells were processed as described in Materials and Methods, and were viewed by electron microscopy. The data sort into three categories, described in the legend to Table 2, that define the position of the bead relative to the COS cell membrane.