Homeostatic proliferation and survival of naive and memory T cells

O Boyman, S Létourneau, C Krieg… - European journal of …, 2009 - Wiley Online Library
O Boyman, S Létourneau, C Krieg, J Sprent
European journal of immunology, 2009Wiley Online Library
The immune system relies on homeostatic mechanisms in order to adapt to the changing
requirements encountered during steady‐state existence and activation by antigen. For T
cells, this involves maintenance of a diverse repertoire of naïve cells, rapid elimination of
effector cells after pathogen clearance, and long‐term survival of memory cells. The
reduction of T‐cell counts by either cytotoxic drugs, irradiation, or certain viruses is known to
lead to lymphopenia‐induced proliferation and restoration of normal T‐cell levels. Such …
Abstract
The immune system relies on homeostatic mechanisms in order to adapt to the changing requirements encountered during steady‐state existence and activation by antigen. For T cells, this involves maintenance of a diverse repertoire of naïve cells, rapid elimination of effector cells after pathogen clearance, and long‐term survival of memory cells. The reduction of T‐cell counts by either cytotoxic drugs, irradiation, or certain viruses is known to lead to lymphopenia‐induced proliferation and restoration of normal T‐cell levels. Such expansion is governed by the interaction of TCR with self‐peptide/MHC (p/MHC) molecules plus contact with cytokines, especially IL‐7. These same ligands, i.e. p/MHC molecules and IL‐7, maintain naïve T lymphocytes as resting cells under steady‐state T‐cell‐sufficient conditions. Unlike naïve cells, typical “central” memory T cells rely on a combination of IL‐7 and IL‐15 for their survival in interphase and for occasional cell division without requiring signals from p/MHC molecules. Other memory T‐cell subsets are less quiescent and include naturally occurring activated memory‐phenotype cells, memory cells generated during chronic viral infections, and effector memory cells. These subsets of activated memory cells differ from central memory T cells in their requirements for homeostatic proliferation and survival. Thus, the factors controlling T‐cell homeostasis can be seen to vary considerably from one subset to another as described in detail in this review.
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