CellVysion Detection Principle

Avidity

Avidity is measured when bound cells are exposed to a shear force for releasing from a surface. It refers to the total binding strength between a cell and a surface when multiple receptor ligand pairs engage simultaneously. 

Affinity

Affinity of antibodies to opsonized cells AND number of recepters per cell determines avidity. It is characterized by the concentraction at 50% coverage of an opsonized cell, KD. In this way an efficacious concentration of a therapeutic antibody candidate can be measured.

Using a novel continuous gradient technique, CellVysion can measure this concentration of 50% coverage (KD).

  • In the CellVysion high quality streptavidin coated sensor chips (SAHC200M, Xantec Bioanalytics GmbH) are applied to generate a continuous ligand density gradient.
  • Patented gradient technology ensures the most accurate real-time data, setting a new standard in antibody and cellular analysis.
  • The unique CellVysion SPR- imager of Vysens determines the cell-avidity and affinity between a ligand-cell receptor in a single experiment!

Continuous gradient generation

  • When the flow is stopped, the cells begin to sediment.
  • Once the flow resumes, two forces act on the cells: the adhesive forces of ligand-cell binding and the opposing loosening forces generated by the flow.
  • Due to the gradient, a point will be reached where binding and loosening are balanced—this is the tipping point expressed as ligand density.
  • The tipping point effectively defines the avidity between antibodies and cells.

A) Continuous antibody gradient (blue to black) on sensor surface

B) The tipping point is generated after sedimentation of cells and a wash

C) A different tipping point is generated with another ligand (red) and cell combination

Actual Avidity

The CellVysion analysis software can now calculate the actual avidity in pg/mm2 from the tipping point.