[CITATION][C] Viruses and T cell turnover: evidence for bystander proliferation

DF TOUGH, J SPRENT - Immunological reviews, 1996 - Wiley Online Library
Immunological reviews, 1996Wiley Online Library
Most T cells activated during typical immune responses differentiate to become short-lived
effector cells which disappear after clearance of antigen (Sprent 1993). However, priming
with antigen generally causes antigen-specific T cells to persist at greater than pre-
immunization levels for long periods of time, thus leading to immunological memory. To
understand the cellular basis for immune memory it is of key importance to determine the
factors which regulate the generation and persistence of memory cells. Two basic …
Most T cells activated during typical immune responses differentiate to become short-lived effector cells which disappear after clearance of antigen (Sprent 1993). However, priming with antigen generally causes antigen-specific T cells to persist at greater than pre-immunization levels for long periods of time, thus leading to immunological memory. To understand the cellular basis for immune memory it is of key importance to determine the factors which regulate the generation and persistence of memory cells.
Two basic mechanisms have been proposed to explain the persistence of memory cells. The first is that memory cells are intrinsically long-lived and require no stimulu. s for their continued survival (Gowans & Uhr 1966). The opposing view Is that, rather than existing autonomously, memory cells require periodic stimulation through their antigen receptors (Gray 1992); this could be mediated by encounter with the original priming antigen, which may persist or be re-introduced to the host, or by cross-reactive environmental antigens. For viruses and CD8* cells, a strict requirement for specific antigen in maintaining memory has been ruled out by the finding that virus-specific CDS" cells persist indefinitely, at least at a population level, after adoptive transfer to virus-free hosts (Lau et al. 1994, Hou et al. 1994). However, as ackowledged by the authors of these studies, the data do not rule out the possibility that memory T cells may persist through low affinity interactions
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