Organization and maintenance of immunological memory by stroma niches.

Immunological memory is still one of the enigmas of modern immunology. We poorly understand the generation of memory cells from their precursors, the lifestyle of memory cells or their maintenance, reactivation and termination. Here, we discuss the recent evidence suggesting that memory plasma cells, as defined in this review, and memory Th cells are maintained in the bone marrow, resting (in terms of proliferation) in survival niches organized by dedicated stroma cells, which control the homeostasis of immunological memory.