Membrane model of endothelial cells and leukocytes. A proposal for the origin of a cortical stress.

Previous models of the erythrocyte membrane have been based on the assumption that the resting curvature of the membrane is either flat or has a small curvature relative to the overall cell dimension. In contrast, several recent experimental observations, both in leukocytes and in endothelial cells, suggest that local regions of the membrane may have high membrane curvature in the resting state. The resting curvature may be of the order of plasmalemmal vesicles in endothelial cells or surface membrane folds on leukocytes. A tension is required to unfold the membrane with strain energy which depends largely on mean curvature. It is proposed that the tendency of endothelial or leukocyte membranes to wrinkle in the unstressed state may provide a restoring force, i.e. a cortical tension.