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IL-2– and IL-7–induced phosphorylation of FOXO3a (top) may promote survival of TCM.

T cells that remember a previously encountered virus are essential in establishing protective immunity. But some T cells have a longer lifetime, and thus effectively a longer immunological memory, than others. Work by Riou et al. (page 79) might explain why effector memory T cells (T_EM) are short lived, whereas central memory T cells (T_CM) are maintained in the body long-term.

The longer-lived T_CM mainly reside in secondary lymphoid organs such as the lymph nodes, whereas the T_EM are found in the peripheral tissues and sites of infection. The exact ontogeny of the two cell types is unknown, but it's thought that T_CM might give rise to the more transient T_EM fighters. Regardless of origin, the biological basis for their different life spans was unknown.

Dendritic cells (DCs) were a good starting point, as they are known to produce the T cell survival factor IL-7. The team added dendritic cells to the two memory cell populations and found that the T_CM proliferation response was more vigorous, perhaps because IL-7 (and IL-2) more efficiently activated the pro-survival factor STAT5 in T_CM.

Even without DCs, T_CM were less susceptible to apoptosis. These cells had less active pro-apoptotic transcription factor FOXO3a and lower transcription of its targets. FOXO3a activity is inhibited by phosphorylation, and adding IL-7 or IL-2 to the T_CM increased FOXO3a phosphorylation at a particular residue, suggesting these cytokines might promote the long-term survival of T_CM by both increasing proliferation and decreasing death.

ruth.williams{at}rockefeller.edu

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Convergence of TCR and cytokine signaling leads to FOXO3a phosphorylation and drives the survival of CD4⁺ central memory T cells

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J. Exp. Med. 2007 204: 79-91. [Abstract] [Full Text] [PDF]

This Article Full Text (PDF, 641K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JEM Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Williams, R. Search for Related Content PubMed Articles by Williams, R. Related Collections Related Article Social Bookmarking                            What's this?