Effects of Neutrophil Pseudopods Generation on the Propulsion Mechanism

Abstract

In vivo, neutrophil motion is known to be propelled by concentration gradient of cytokine. However, the mechanism of propulsion has not been elucidated yet in the previous research. Based on the assumption that neutrophil is propelled by the concentration Marangoni effect, concentration gradient of cytokine on the neutrophil membrane and the neutrophil motion is investigated experimentally. In our previous investigations, it was found that neutrophil generate pseudopods for infiltration of organs near the wall. In this study, to investigate the phenomenon that neutrophil pseudopods generation near the wall, a microscopy-based observation experiment is conducted. The distance between the neutrophils and the wall and geometrical characteristics of the neutrophils are measured. From the results, the following three findings were obtained. First, arithmetic mean roughness and root mean square roughness are higher at distances of 2 and 4 μm from the wall surface. Second, skewness and kurtosis are highest value at distances of 2 μm from the wall surface. Third, neutrophil generates pseudopods at 4 μm from the wall surface and completely change shape at 2 μm. These findings suggest that near-wall interactions promote pseudopod-induced roughening that is likely to influence transport on the neutrophil membrane and, consequently, propulsion in cytokine gradients.