Lateral phase separation of lipids in plasma membranes: effect of temperature on the mobility of membrane antigens.

Cooling populations of newly formed mouse human heterokaryons has effects on the intermixing of mouse and human surface antigens which indicate the occurrence of phase separations in membrane lipids. Antigen mixing, previously shown to be due to diffusion in the plane of the membrane, is retarded when cells are cooled from 37 degrees to 21 degrees C, but is then speeded by further cooling to 15 degrees C. This result is in accord with observations on phase separations of lipids in artificial and bacterial membranes.