Abstract

Currently, around 120 therapeutic antibodies have obtained market approval and around 1,000 are in various stages of clinical development [1]. The interactions between antibodies and cells are playing a central role in their efficacy. These interactions are governed by the avidity of cells and antibodies. In recent studies, more and more emphasis is laid on the avidity aspects of cells versus antibodies [2]. The optimal accuracy of the avidity in terms of equilibrium constants is obtained under low densities of ligands present on a sensor surface.

Recently, a novel Surface Plasmon Resonance imaging technique has been applied that employs a gradient of ligand density [3]. In this brief paper, we show an additional way of exploiting the ligand density gradient, namely for cell avidity measurement. As an example, we measured the specific binding of the LNCaP cell line using their EpCAM (Epithelial Cell Adhesion Molecule) receptor on a gradient of anti-EpCAM antibodies. One can observe the location where cells are still captured at a so-called tipping point. The functional ligand density at the tipping point after cell binding and controlled shear conditions are typical for a certain combination of anti-cell receptor antibodies with a certain cell line.

Keywords:EpCAM; Anti-cell receptor; CellVysion SPR imager