A modified micropipette aspiration technique and its application to tether formation from human neutrophils

Tether formation, which is mechanically characterized by its threshold force and effective viscosity, is involved in neutrophil emigration from blood circulation. Using the micropipette aspiration technique, which was improved by quantitative contact control and computerized data analysis, we extracted tethers from human neutrophils treated with IL-8, PMA, or cytochalasin D. We found that both IL-8 and PMA elevated the threshold force to about twice as large as the value for passive neutrophils. All these treatments decreased the effective viscosity dramatically (∼80%). With a novel method, the residual cortical tension of the cytochalasin-D-treated non-spherical neutrophils was measured to be ∼8.8 pN/μm.