T cell homeostasis requires G protein-coupled receptor-mediated access to trophic signals that promote growth and inhibit chemotaxis

Eur J Immunol. 2005 Mar;35(3):786-95. doi: 10.1002/eji.200425729.

Abstract

Signals that regulate T cell homeostasis are not fully understood. G protein-coupled receptors (GPCR), such as the chemokine receptors, may affect homeostasis by direct signaling or by guiding T cell migration to distinct location-restricted signals. Here, we show that blockade of Galphai-associated GPCR signaling by treatment with pertussis toxin led to T cell atrophy and shortened life-span in T cell-replete hosts and prevented T cell homeostatic growth and proliferation in T cell-deficient hosts. In vitro, however, neither GPCR inhibition nor chemokine stimulation affected T cell atrophy, survival, or proliferation. These findings suggest that GPCR signals are not trophic stimuli, but instead may be required for migration to distinct trophic signals, such as IL-7 or self-peptide/MHC. Surprisingly, while chemokines did not affect atrophy, atrophic T cells displayed increased chemokine-induced chemotaxis that was prevented by IL-7 and submitogenic anti-CD3 antibody treatment. This increase in migration was associated with increased levels of GTP-bound Rac and the ability to remodel actin. These data suggest a novel mechanism of T cell homeostasis wherein GPCR may promote T cell migration to distinct location-restricted homeostatic trophic cues for T cell survival and growth. Homeostatic trophic signals, in turn, may suppress chemokine sensitivity and cytoskeletal remodeling, to inhibit further migration.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / immunology
  • Actins / metabolism
  • Adoptive Transfer
  • Animals
  • Atrophy / immunology
  • Blotting, Western
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Chemotaxis / immunology*
  • Cytoskeleton / immunology
  • Cytoskeleton / metabolism
  • Flow Cytometry
  • Growth Substances / immunology*
  • Homeostasis / immunology*
  • Interleukin-7 / immunology
  • Interleukin-7 / metabolism
  • Lymphoid Tissue / pathology
  • Mice
  • Pertussis Toxin / pharmacology
  • Receptors, Antigen, T-Cell / immunology
  • Receptors, Antigen, T-Cell / metabolism
  • Receptors, Cytokine / immunology
  • Receptors, G-Protein-Coupled / immunology*
  • T-Lymphocytes / drug effects
  • T-Lymphocytes / immunology*

Substances

  • Actins
  • Growth Substances
  • Interleukin-7
  • Receptors, Antigen, T-Cell
  • Receptors, Cytokine
  • Receptors, G-Protein-Coupled
  • Pertussis Toxin