Visualization and dynamic analysis of host–pathogen interactions

• The dynamic spatial behavior of T cells is essential to their protective function.
• Novel imaging techniques enable visualization of T cell migration and cellular interactions in situ.
• Positioning within and recirculation between lymphoid organs impacts surveillance.
• Pathogens have general and specific effects on T cell migration and recirculation.
• Migratory patterns and effector delivery are linked in effective pathogen clearance.

To contain invading microbes, the immune system must efficiently recognize the presence of the invader, mobilize cells to the site of infection, and deploy effector function. Rare antigen-specific T cells must find small numbers of antigen-presenting cells, proliferate and differentiate in secondary lymphoid tissues, then traffic to the infected site and be activated by antigen again to contribute to host defense. Our understanding of the dynamic processes involved has benefited enormously from tools that enable the visualization of cell location and behavior in complex tissue environments. Here we summarize recent insights into T cell trafficking and migration through secondary lymphoid organs and at peripheral infection sites, highlighting cell-intrinsic and extrinsic factors optimizing antigen surveillance at steady-state and delivery of an effector response during infection.