Locally produced C5a binds to T cell expressed C5aR to enhance effector T-cell expansion by limiting antigen-induced apoptosis

  • Lalli P
  • Strainic M
  • Yang M
 et al. 
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Our recent studies have shown that immune cell-produced complement provides costimulatory and survival signals to naive CD4(+) T cells. Whether these signals are similarly required during effector cell expansion and what molecular pathways link locally produced complement to T-cell survival were not clarified. To address this, we stimulated monoclonal and polyclonal T cells in vitro and in vivo with antigen-presenting cells (APCs) deficient in the complement regulatory protein, decay accelerating factor (DAF), and/or the complement component C3. We found that T-cell expansion induced by DAF-deficient APCs was augmented with diminished T-cell apoptosis, whereas T-cell expansion induced by C3(-/-) APCs was reduced because of enhanced T-cell apoptosis. These effects were traced to locally produced C5a, which through binding to T cell-expressed C5aR, enhanced expression of Bcl-2 and prevented Fas up-regulation. The results show that C5aR signal transduction in T cells is important to allow optimal T-cell expansion, as well as to maintain naive cell viability, and does so by suppressing programmed cell death.

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  • Peter N. Lalli

  • Michael G. Strainic

  • Min Yang

  • Feng Lin

  • M. Edward Medof

  • Peter S. Heeger

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