The fundamental motor of the human neutrophil is not random: evidence for local non-Markov movement in neutrophils.

The search for a fundamental mechano-chemical process that results in net cell motion has led investigators to fit neutrophil tracking data to well described physical models in hopes of understanding the functional form of the driving force. The Ornstein-Uhlenbeck (OU) equation for mean square displacement describes a locally persistent and globally random process and is often used as a starting point for analysis of neutrophil displacements. Based upon the apparently close fit of neutrophil tracking data to this equation and the nature of its derivation, biologists have inferred that the motor of the neutrophil is best represented as a random process. However, 24 of 37 neutrophil paths that we investigated preferentially display programmatic rather than Markov short term correlations between displacements or turn angles. These correlations reflect a bimodal rather than a uniform distribution of subpath correlations in the two variables, and are strongly sampling rate-dependent. Significant periodic components of neutrophil shape change are also detected at the same time scale using either Fourier or elliptical Fourier transform-based descriptors of the neutrophil perimeter. Oscillations in neutrophil velocity have the same period. Taken together, these data suggest a nonstochastic, and perhaps periodic, component to the process driving neutrophil movement.

Development of a shape vector that identifies critical forms assumed by human polymorphonuclear neutrophils during chemotaxis.

Human polymorphonuclear neutrophils undergo characteristic shape changes that are critical to their ability to move and ingest their targets. We present here the construction of a simple shape vector, calculated from the coordinates of the cell perimeter, that can identify critical forms that a neutrophil assumes during the course of ameboid movement. The vector can be used to find neutrophils of a specific shape from the image analyzer data produced during a typical neutrophil tracking experiment.