Migration of immune cells is believed to be optimized in the course of evolution to reduce their search time. Nevertheless, so far the optimality of the search for pathogens and other targets by immune cells has not been verified. In a combined theoretical and experimental approach, projects A7 (Shaebani), A8 (Santen), and A10 (Lautenschläger) verified that the coupling between directional persistence and migration speed enables dendritic cells to search for pathogens more efficiently. Mediated by retrograde actin flows, the speed of migrating cells is coupled to their directional persistence (i.e. the straightness of trajectories) in such a way that they decelerate to change the direction of motion. Shaebani et al. have shown that such a correlated dynamic enables immune cells to reduce their search time. A new class of optimal search strategies is introduced based on tuning the strength of coupling between factors influencing the search efficiency and it is shown that the correlated motion is advantageous for optimizing search efficiency when the persistence length of the searcher is much smaller than the size of the environment in which they search. Understanding the mechanisms of adaptive search and clearance in the immune system opens the way toward more effective cancer immunotherapies and vaccine design. These findings also may open new possibilities to design artificial intelligent searchers. The study has been published in Physical Review Letters.

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