The Rheological Impact of Cell Activation on the Flow Behavior of Neutrophils

OF THESIS THE RHEOLOGICAL IMPACT OF ACTIVATION ON THE FLOW BEHAVIOR OF NEUTROPHILS Previously, it was reported that the morphological changes (pseudopod projection) that circulating neutrophils adopt due to cell activation raises peripheral vascular resistance by disrupting microvascular rheology. Studies utilized murine muscle preparations to link neutrophil pseudopod formation to cell activation and a viscous impact on hemodynamic resistance. But because of the complexity associated with the organization of the vasculature and microvasculature in tissues, it was unclear whether the effects of neutrophil activation on hemodynamic resistance were associated with the macro-/microcirculation. This research describes an in vitro analysis using viscometry and microvascular network mimics (microporous membranes) to assess the rheological impact of pseudopods on capillary-like flow. Suspensions of neutrophil-like HL-60 promyelocytes (dHL60’s) and human neutrophils, stimulated with 10 nM fMLP were used, with/without hematocrit. Stimulation of dHL60s or human neutrophils with fMLP altered their flow behavior, which was detected as an increase in solution viscosity. Addition of hematocrit negated the effect of neutrophil activation on suspension viscosity. Moreover, cell activation increased the resistance of microporous membranes to flow of neutrophil suspensions with addition of hematocrit exacerbating this effect. Combined, the results of this study provided evidence that activated neutrophils influence microscale flow resistance via a rheological impact.