Novel innate immune functions revealed by dynamic, real-time live imaging of bacterial infections.

A bacterial infection is accompanied by dynamic alterations in tissue homeostasis within the infected organ. What starts as a local bacterium-host cell interaction at the site of infection changes over time to include distant signaling and the engagement of multiple cell types in an effort to eradicate the bacteria. Recent advancements in imaging technologies, such as multiphoton microscopy, provide new tools to visualize the realtime dynamics of infection within the living host. The use of live animal models means that all of the interplaying factors, such as the immune, lymphatic, nervous, and vascular systems, are present and can be accounted for. This review describes novel insights of innate immune defense mechanisms obtained using real-time visualization of the infected tissue in a live animal model. This emerging field of "tissue microbiology" will provide data that, when combined with the massive knowledge base generated from research in "cellular microbiology," will provide a more complete picture of the complex infection process.