Microrheological assessment of neutrophil mechanical properties in adhesion in a model capillary

There has been considerable debate on the relative importance of biochemical stimuli and mechanical deformation in neutrophil adhesion in lung capillaries, a process observed following bacterial infection in the body. Recently a micropipette assay has been developed to act as a flow chamber for the capillaries in the lung, so that the effect of adhesion molecules (such as ICAM‐1) on adhesion and cell mechanical properties can be observed. The microrheology technique that involves tracking and analysing the thermal motion of endogenous granules within neutrophils is used to extract non‐invasively the intracellular viscoelastic moduli. The data indicate that the central body region is significantly stiffer than the two end cap regions which do not differ significantly in stiffness from each other. All regions are stiffer in ICAM‐1‐coated micropipettes than in BSA‐coated micropipettes. These results provide insight into the regional rheological effects of deformation and adhesion molecules on neutrophils. This work is supported by an award from the American Heart Association, National Science Foundation CAREER grant BES‐0547165 (DFJT) and National Institutes of Health grant GM‐057640 (DJG).