Some physical chemical aspects of receptor-ligand interactions.

Quantitative evaluations of a variety of binding reactions of interest to immunologists have usually assumed that the reactants are homogenously dispersed in solution for purposes of calculation. In fact, many of these reactions involve cell-bound "receptors" which are present at exceedingly high local concentrations on discrete particles. We describe how such a distribution can influence the experimentally measured binding constants. We also briefly consider the additional complexities introduced when multipoint attachment between the ligand and cell-bound receptors is possible, and discuss the possible biological implications.