Evaluation of Neutrophil’s Rotation on Transport Process of Membrane Concentration and its Underwater Propulsion by CFD Analysis

In the immunological systems, neutrophil propulsion is driven by the concentration gradient of cytokines. However, there is no quantitative relationship between concentration gradient and propulsion. In our previous study, assuming that neutrophil moves by the concentration Marangoni effect, the concentration gradient of cytokine on the neutrophil membrane was experimentally examined. The results showed that the cytokine concentration gradient on the neutrophil membrane changed periodically. It was suggested that neutrophils move while rotating under cytokine concentration gradient. However, observation of neutrophil rotation has been limited experimental validation due to the accuracy and sensitivity of current measurement systems. For these reasons, evidence of a relationship between neutrophil propulsion and rotation has not been found. In this study, assuming that the neutrophil is rotating, the simulation of concentration transport around neutrophils with and without half rotation is done. From these results, it was found that (1) without rotation, after cytokines adhesion to the front side of the neutrophil, the concentration distribution on the membrane does not change with time, (2) with rotation, cytokine concentration on the membrane periodically changes and (3) the concentration gradient on the membrane is affected by the rotation and adsorption/desorption function of neutrophils. From these findings, it was concluded that neutrophil rotation is an important role in neutrophil’s propulsion mechanism.