The dynamics of immunological memory

Memory has long been thought of as a stable phenomenon within the immune system: once generated it lasts for a very long time. This static view of immunological memory predicts that an established population of memory cells is independent of outside influences. Recent findings, concerning the population kinetics of the peripheral pool of lymphocytes and, more directly, concerning the influence of antigen on memory cell survival, are forcing us to reassess this idea. I present here a dynamic view of immunological memory which takes into account an immune system that appears in continual flux and whose constituent cells may rely upon recurrent signals for their survival. This view of memory also makes certain predictions and these are considered.