Adsorption of concanavalin A on human platelets.

A physiological cell surface adsorption system approach is investigated on human platelets utilizing mathematical modeling. Monodispersed washed platelets are freshly collected in an isotonic buffer as a suspension utilizing a gel filtration technique. Concanavalin A is used as a glycoprotein receptor adsorbate in the adsorption studies. Three mathematical models are proposed based on simple chemical equilibrium reactions between adsorbate and cell surface receptors in an effort to explain concanavalin A - platelet surface glycoprotein interaction. Model I assumes that all receptors are undergoing simultaneous surface reactions with the adsorbate and without correlation. Model II reflects a strong correlation between the receptors, when only one receptor is active and the second receptor(s) is nothing but the combination of first receptor-adsorbate complex. Model III assumes the presence of multiple receptors on the cell surface. Only when a specific fraction of the total number of one receptor have reacted, will the other receptor(s) initiate reaction with the adsorbate. The results suggest the existence of at least three major glycoprotein receptors interacting with the lectin, and having different equilibrium constants as indicated in the adsorption isotherm. Model III seems to support best the experimental data of concanavalin A interaction with platelet surface glycoproteins.