Alteration of mammalian cells by interaction with artificial lipid vesicles

Artificial lipid vesicles interact with a variety of mammalian cells, including blood cells, spleen cells, and tumor cells, and during this interaction components can be transferred from the vesicle to the cell and from the cell to the vesicle. Transfer of intravesicular material is observed when artificial lipid vesicles carrying an intravesicular marker, 99mTc (as TcO4- ion), are incubated with mammalian cells. When vesicles prepared with [14C] phospholipid are incubated with mammalian cells, the labeled lipid is also transferable to mammalian cells. Conversely, if the mammalian cell surface is radiolabeled (with 125I), the cell marker is in part transferable to the vesicles. Thus, interaction of mammalian cells with vesicles alters the characteristics of the cell in several ways. There is a loss of some cell surface components, a gain of vesicle lipid components, and an acquisition of intravesicular contents. Such alteration may affect the biological behavior of the cell in vivo. Thus, the in vivo distribution in the mouse of isologous red blood cells is altered after interaction with vesicles; the liver and spleen remove large proportions of such cells in comparison to control erythrocytes labeled with 51Cr. The behavior of vesicle survivors from a cell interaction is also altered. Upon reexposure of such vesicles to a fresh population of cells, the intravesicular marker is no longer transferable to cells; and upon injection of such vesicles into mice, the liver accumulation of vesicular label is reduced as compared with that of nonincubated vesicles.