Whole-body analysis of T cell responses.

In vivo methods to detect antigen-specific T cell responses at the single-cell level have greatly increased our knowledge of how the immune system works. However, most of these approaches have been confined to analysis of lymphoid tissues. Recently, the development of imaging techniques capable of simultaneously monitoring all the tissues of the body has led to the realization that antigen-experienced T cells reside in non-lymphoid tissues and may play a vital role in protecting the host against pathogens. Therefore, single-cell imaging at the level of the whole organism is needed to fully understand the dynamics of protective immunity.