Quantitative Image Analysis in the Study of Neutrophil and Neutrophil-Like HL-60 Chemotaxis




Zhang-Velten, Elizabeth Ren

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Neutrophils are fast-moving first responders of the innate immune system. External chemoattractant signals result in neutrophil polarization: the neutrophil forms a leading edge (front) which constantly protrudes and retracts actin-rich pseudopods, and a contractile myosin-enriched trailing edge (back) which is insensitive and directionally persistent. Previous work has suggested that polymerized actin and contractile actomyosin segregate to the neutrophil's morphological front and back, respectively, due to mutual inhibition. Beyond this initial establishment of spatially segregated domains, however, many questions remain unclear. In this work, I address two questions: (i) first, how do the front and back of the neutrophil demonstrate seemingly uncoupled behaviors despite these inhibitory links? (ii) and, second, at what fMLP concentration does neutrophil chemotaxis saturate, and how is this maximal concentration determined? With quantitative analysis of immunofluorescent fixed-cell images and live-cell migration videos, I demonstrate the role of microtubules in insulating the front and back modules of chemotactic neutrophils, and the role of ERK in driving neutrophil migration into maximal fMLP concentrations.

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