Persistence-Speed Coupling Enhances the Search Efficiency of Migrating Immune Cells

TL;DR

This paper demonstrates that coupling between persistence and speed in migrating immune cells enhances their search efficiency, supported by experimental data and theoretical modeling of mean first-passage time in confined spaces.

Contribution

It introduces a new theoretical framework for optimizing search strategies by coupling persistence and speed, validated through experiments and analytical calculations.

Findings

Persistence-speed coupling reduces search time in immune cells.

Correlated motion improves search efficiency when persistence length is short.

Positive persistence-speed correlation can increase search time at high persistence lengths.

Abstract

Migration of immune cells within the human body allows them to fulfill their main function of detecting pathogens. Adopting an optimal navigation and search strategy by these cells is of crucial importance to achieve an efficient immune response. Analyzing the dynamics of dendritic cells in our in vitro experiments reveals that the directional persistence of these cells is highly correlated with their migration speed, and that the persistence-speed coupling enables the migrating cells to reduce their search time. We introduce theoretically a new class of random search optimization problems by minimizing the mean first-passage time (MFPT) with respect to the strength of the coupling between influential parameters such as speed and persistence length. We derive an analytical expression for the MFPT in a confined geometry and verify that the correlated motion improves the search efficiency if the mean persistence length is sufficiently shorter than the confinement size. In contrast, a positive persistence-speed correlation even increases the MFPT at long persistence length regime, thus, such a strategy is disadvantageous for highly persistent active agents.