In vivo imaging using bioluminescence: a tool for probing graft-versus-host disease.

Immunological reactions have a key role in health and disease and are complex events characterized by coordinated cell trafficking to specific locations throughout the body. Clarification of these cell-trafficking events is crucial for improving our understanding of how immune reactions are initiated, controlled and recalled. As we discuss here, an emerging modality for revealing cell trafficking is bioluminescence imaging, which harnesses the light-emitting properties of enzymes such as luciferase for quantification of cells and uses low-light imaging systems. This strategy could be useful for the study of a wide range of biological processes, such as the pathophysiology of graft-versus-host and graft-versus-leukaemia reactions.