Chemical synthesis of a two-photon-activatable chemokine and photon-guided lymphocyte migration in vivo

Chemokine-guided lymphocyte positioning in tissues is crucial for normal operation of the immune system. Direct, real-time manipulation and measurement of single-cell responses to chemokines is highly desired for investigating the cell biology of lymphocyte migration in vivo . Here we report the development of the first two-photon-activatable chemokine CCL5 through efficient one-pot total chemical synthesis in milligram scale. By spatiotemporally controlled photoactivation, we show at the single-cell level that T cells perceive the directional cue without relying on PI3K activities, which are nonetheless required for persistent migration over an extended period of time. By intravital imaging, we demonstrate artificial T-cell positioning in cutaneous tissues and lymph nodes. This work establishes a general strategy to develop high-quality photo-activatable protein agents through tailor-designed caging of multiple residues and highlights the potential of photo-activatable chemokines for understanding and potential therapeutic manipulation of cell positioning and position-controlled cell behaviours in vivo . The precise spatiotemporal control of chemokine exposure would be an advantageous tool for immune cell research. Here, Chen et al. develop a two-photon-activatable chemokine CCL5 and use it to direct lymphocyte migration in vivo and to show that PI3-kinase is not required to sense a gradient in vitro .