Preface

Researchers have used a variety of techniques over the past century to gain fundamental insights in the field of immunology and, as technology has advanced, so too has the ability of researchers to delve deeper into the biological mechanics of immunity. The immune system is exceedingly complex and must patrol the entire body to protect us from foreign invaders. This requires the immune system to be highly mobile and adaptable able to respond to diverse microbial challenges while maintaining the ability to distinguish self from a foreign invader. This latter feature is of great importance because the immune system is equipped with toxic mediators, and a failure in self/non-self discrimination can result in serious diseases. Fortunately, in most cases, the immune system operates within the framework of its elegant design and protects us from diverse microbial challenges without initiating disease. Because the immune system is not confined to a single tissue, a comprehensive understanding of immunity requires that research be conducted at the molecular, cellular, and systems level. Immune cells often find customized solutions to handling microbial insults that depend on the tissue(s) in which the pathogen is found. Removal of immune cells from their natural environment is one common means by which immunity is studied; however, this approach comes with the caveat that immune cells interact uniquely with the microenvironments and tissue architecture they encounter. Because no two tissues are alike, immune cells will often adapt and respond based on the unique microenvironment in which they reside. Given this fact, it is of great importance to consider cellular context when deciphering the mysteries of the immune system. Lessons learned in one tissue may not necessarily apply to the entire body. Understanding the contextual side of immunity necessitates study of immune cells in vivo. However, those that pursue in vivo research immediately encounter the obstacle of how best to study immune cells in their natural environments. This obstacle is not a trivial one, as it is far easier to remove cells from their natural environments and study them ex vivo or in vitro. Fortunately, scientists in other disciplines have come to the rescue with exciting advances in imaging techniques. These advances have enabled immunologists to quite literally “see” how immune cells respond to diverse challenges. Using static imaging approaches, researchers have captured snapshots in time, which are then pieced together with