Scientists have long believed that immunological memory--the record of infections past--is maintained by highly differentiated T cells and B cells that were generally thought to reside in the spleen and lymph nodes, the secondary lymphoid organs. Thus, the lymph nodes and blood (considered a surrogate for the spleen) are typically used to probe the long-term effects of immunological challenge. But as it turns out, these memory seekers may have been looking in all the wrong places.
In this issue's Hot Papers, two research teams, using different but complementary techniques, discovered that nonlymphoid tissues such as the lungs and fat pads also harbor memory T cells. These cells seem to respond to antigenic rechallenge differently than their counterparts in the spleen and lymph nodes.
"The magnitude of the populations of memory cells that you could find in these nonlymphoid tissues hadn't been appreciated," says Leo Lefrançois, of the University of Connecticut ...
