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The combined-immunotherapy of adoptive cell therapy (ACT) and cyclophosphamide (CTX) is one of the most efficient treatments for melanoma patients. However, no synergistic effects of CTX and ACT on the spatio-temporal dynamics of immunocytes in vivo have been described. Here, we visualized key cell events in immunotherapy-elicited immunoreactions in a multicolor-coded tumor microenvironment, and then established an optimal strategy of metronomic combined-immunotherapy to enhance anti-tumor efficacy. Intravital imaging data indicated that regulatory T cells formed an 'immunosuppressive ring' around a solid tumor. The CTX-ACT combined-treatment elicited synergistic immunoreactions in tumor areas, which included relieving the immune suppression, triggering the transient activation of endogenous tumor-infiltrating immunocytes, increasing the accumulation of adoptive cytotoxic T lymphocytes, and accelerating the infiltration of dendritic cells. These insights into the spatio-temporal dynamics of immunocytes are beneficial for optimizing immunotherapy and provide new approaches for elucidating the mechanisms underlying the involvement of immunocytes in cancer immunotherapy.DOI: http://dx.doi.org/10.7554/eLife.14756.001

Immune responses are based on the coordinated searching behaviors of immunocytes that are aimed at tracking down specific targets. The search efficiency of immunocytes significantly affects the speed of initiation and development of immune responses. Previous studies have shown that not only the intermittent walk but also the zigzag turning preference of immunocytes contributes to the search efficiency. However, among existing models describing immunocytes' search strategy, none has captured both features. Here we propose a zigzag generalized Lévy walk model to describe the search strategy of immunocytes more accurately and comprehensively by considering both the intermittent and the zigzag-turning walk features. Based on the analysis of the searching behaviors of typical immune cell types, dendritic cells and leukocytes, in their native physiological environment, we demonstrate that the model can describe the in vivo search strategy of immunocytes well. Furthermore, by analyzing the search efficiency, we find that this type of search strategy enables immunocytes to capture rare targets in approximately half the time than the previously proposed generalized Lévy walk. This study sheds new light on the fundamental mechanisms that drive the efficient initiation and development of immune responses and in turn may lead to the development of novel therapeutic approaches for diseases ranging from infection to cancer.

Layered metal hydroxides (LMHs) are promising catalysts for oxygen evolution reaction. However, the hydrogen evolution reaction (HER) activity of LMHs is unsatisfactory due to their poor conductivity and limited active sites. Herein, taking Ni(OH)2 as demonstration, a novel “one stone five birds” plasma activation strategy synergistic with Ru single atoms (Ru SAs) doping is developed to boost the HER activity of Ni(OH)2 by constructing heterostructured β‐Ni(OH)2/Ni‐Ru SAs nanosheet arrays (NSAs). Benefiting from the structural/compositional features and optimized electronic state, the as‐obtained β‐Ni(OH)2/Ni‐Ru SAs NSAs exhibit splendid HER activity with a low overpotential of 16 mV at 10 mA cm−2 and a small Tafel slope of 21 mV dec−1 in alkaline solution. Excellent HER performance in alkaline seawater and neutral solutions are also demonstrated by the β‐Ni(OH)2/Ni‐Ru SAs NSAs. The plasma activation and Ru SAs doping play important roles in enhancing water adsorption and accelerating the kinetics of water dissociation. Density functional theory (DFT) calculations reveal that the introduction of Ru SAs in the system facilitates the generation of surface OH vacancies for providing more active sites as well as decreases the antibonding state density of the generated mid‐gap state for enhancing H adsorption strength toward the optimal range.

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