T cell motility within lymph nodes fits a Levy signature (CAM1P.225)

Abstract

Abstract Naïve T cell motility within lymph nodes (LNs) is crucial for the initiation of the T cell response. Multiphoton imaging has allowed direct visualization of T cell movement in LNs, demonstrating T cell search as a random walk. Different types of random walks exist in biological systems, including Brownian and Levy walks. Levy walks differ from Brownian walks by the presence of large steps, and naïve T cell motility in LNs had been assumed to be a Brownian walk. Recent evidence suggests that the motility of T cells in the brain is characterized by a Levy signature, not a Brownian walk. However, detailed analysis naïve T cells search within LNs has not been done. Here we present evidence that naïve T cells use a Levy signature to search in LNs. Using multiphoton microscopy, we determined displacement and step size taken by naive T cells in LNs. We find that naïve T cell motility show a heavy-tailed distribution characteristic of a Levy signature. However, we do not observe a classical Levy walk as defined by a power-law fit. Instead, the best fit for T cell motility is a log-normal distribution. We then used computer modeling to assess the efficiency of T cell search parameters. We find that heavy-tailed distributions are as efficient as the classical Levy walk at target search. These findings shed new light on the fundamental mechanisms driving T cell search for antigen within lymph nodes.