Imaging tolerance

The behavior of naive T cells in the lymph nodes does not betray their fate, according to new footage from live lymph nodes. On page 1815, Zinselmeyer and colleagues show that the movements of CD4⁺ T cells destined for tolerance differ only subtly from those destined for priming, suggesting that tolerance cannot be explained by an overt failure of the T cells to stop so that they can receive a priming signal.Intravital imaging technology has revealed that naive T cells dart rapidly around lymph nodes in search of their antigen, briefly contacting antigen presenting cells (APCs) as they go. An encounter with a cognate antigen delivers a stop signal that triggers stable T cell–APC interactions. When this encounter breaks up, the...