Micropipette adhesion frequency assay
Measures adhesion frequency of single receptor-ligand interactions
The initial contact between membrane bound surface molecules govern interactions between cells. In the case of selectins and integrins on the endothelium, binding to carbohydrate ligands on flowing leukocytes initiates transmigration into underlying tissues. The micropipette adhesion frequency assay allows for control of the approach and retraction, as well as the duration of contact between a cell expressing a molecule of interest and a red blood cell coated with the ligand to that molecule. The microscopically visible frequency of adhesion events between these molecules is used to extract kinetic parameters such as the 2D affinity and the off-rate of the bond. These parameters characterize the interactions between surface molecules in a relevant biological setting.