First-order transition between adhesion states in a system mimicking cell-tissue interaction

We establish a model of cell-tissue interaction consisting of vesicles carrying lipopolymers (to mimic the glycocalix) and mobile specific ligands of the blood platelet integrin alpha (IIb)beta (3) coveringthe substrate. We find the phase diagram with a first-order transition between a gravity-controlled weak state of the vesicle-substrate adhesion and a strong-adhesion state governed by receptor-ligand interaction. Adhesion energy epsilon (adh) is measured as a function of ligand and repeller concentration by interferometric contour analysis on the basis of a new refined model of soft shell adhesion (accounting for the membrane bending and stretching at the adhesion rim of the ellipsoidal vesicle). At ligand densities comparable to integrin density, epsilon (adh) decreases sharply. Increasing the repeller content weakens the adhesion strength.