In vivo imaging of lymphocyte trafficking.

Over the past decades, intravital microscopy (IVM), the imaging of cells in living organisms, has become a valuable tool for studying the molecular determinants of lymphocyte trafficking. Recent advances in microscopy now make it possible to image cell migration and cell-cell interactions in vivo deep within intact tissues. Here, we summarize the principal techniques that are currently used in IVM, discuss options and tools for fluorescence-based visualization of lymphocytes in microvessels and tissues, and describe IVM models used to explore lymphoid and non-lymphoid organs. The latter will be introduced according to the physiologic itinerary of developing and differentiating T and B lymphocytes as they traffic through the body, beginning with their development in bone marrow and thymus and continuing with their migration to secondary lymphoid organs and peripheral tissues.