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Mechanistic insights into impaired dendritic cell function by rapamycin: inhibition of Jak2/Stat4 signaling pathway

Po-Hui Chiang1, Lianfu Wang, C Andrew Bonham

  • 1Thomas E. Starzl Transplantation Institute and Department of Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA 15261, USA.

Journal of Immunology (Baltimore, Md. : 1950)
|January 22, 2004
PubMed

Insights

Rapamycin suppresses dendritic cell (DC) immunostimulatory activity by inhibiting IL-12 signaling via Stat4, leading to impaired T cell responses and prolonged allograft survival. This impacts understanding of rapamycin

Area of Science:

  • Immunology
  • Transplantation immunology

Background:

  • Rapamycin's effect on T cells is known, but its impact on antigen-presenting cells (APCs), specifically dendritic cells (DCs), remains less understood.
  • Dendritic cells are crucial for initiating immune responses, including T cell activation and allograft rejection.

Purpose of the Study:

  • To investigate the suppressive effects of rapamycin on the immunostimulatory function of dendritic cells.
  • To elucidate the molecular mechanisms underlying rapamycin-induced DC dysfunction.

Main Methods:

  • Treatment of B10 dendritic cells (DCs) with rapamycin (rapa-DC).
  • Assessment of rapa-DC allostimulatory activity using T cell proliferation and cytotoxic T lymphocyte (CTL) assays.
  • Analysis of DC expression of MHC class II, costimulatory molecules, IL-12, NF-kappaB pathway, IL-12R, IL-18Ralpha/beta, and signaling molecules JAK2/Stat4.
  • Evaluation of allograft survival in rapamycin-treated recipients.

Main Results:

  • Rapamycin-treated DCs (rapa-DC) exhibited suppressed immunostimulatory activity, leading to reduced T cell proliferation and CTL responses.
  • rapa-DC administration significantly prolonged cardiac allograft survival.
  • Rapamycin did not affect DC expression of MHC class II, costimulatory molecules, or IL-12 production, nor did it inhibit the NF-kappaB pathway.
  • IL-12 signaling through JAK2/Stat4 was markedly suppressed in rapa-DC, and Stat4-deficient DCs showed similar poor allostimulatory activity.
  • Rapamycin inhibited IFN-gamma production, but this was not the sole cause of DC dysfunction.
  • Rapamycin suppressed IL-18 receptor expression, potentially down-regulating DC IL-12 autocrine activation.

Conclusions:

  • Rapamycin suppresses dendritic cell immunostimulatory function, primarily by inhibiting IL-12 signaling via the Stat4 pathway.
  • This suppression of DC function contributes to impaired T cell responses and prolonged allograft survival.
  • The findings highlight a novel mechanism of rapamycin action impacting innate immune cells and transplantation outcomes.

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