TLR9 signaling in fibroblastic reticular cells regulates peritoneal immunity
Li Xu, … , Timothy R. Billiar, Meihong Deng
Li Xu, … , Timothy R. Billiar, Meihong Deng
Published August 5, 2019
Citation Information: J Clin Invest. 2019;129(9):3657-3669. https://doi.org/10.1172/JCI127542.
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TLR9 signaling in fibroblastic reticular cells regulates peritoneal immunity

Abstract

Fibroblastic reticular cells (FRCs), a subpopulation of stromal cells in lymphoid organs and fat-associated lymphoid clusters (FALCs) in adipose tissue, play immune-regulatory roles in the host response to infection and may be useful as a form of cell therapy in sepsis. Here, we found an unexpected major role of TLR9 in controlling peritoneal immune cell recruitment and FALC formation at baseline and after sepsis induced by cecal ligation and puncture (CLP). TLR9 regulated peritoneal immunity via suppression of chemokine production by FRCs. Adoptive transfer of TLR9-deficient FRCs more effectively decreased mortality, bacterial load, and systemic inflammation after CLP than WT FRCs. Importantly, we found that activation of TLR9 signaling suppressed chemokine production by human adipose tissue–derived FRCs. Together, our results indicate that TLR9 plays critical roles in regulating peritoneal immunity via suppression of chemokine production by FRCs. These data form a knowledge basis upon which to design new therapeutic strategies to improve the therapeutic efficacy of FRC-based treatments for sepsis and immune dysregulation diseases.

Authors

Li Xu, Yiming Li, Chenxuan Yang, Patricia Loughran, Hong Liao, Rosemary Hoffman, Timothy R. Billiar, Meihong Deng

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Figure 3

TLR9 inhibits peritoneal B cell recruitment via suppressing CXCL13 production.

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TLR9 inhibits peritoneal B cell recruitment via suppressing CXCL13 produ...
(A) WT and Tlr9–/– mice were subjected to CLP. PLF was collected at 18 hours after CLP. Peritoneal CXCL13 levels were assessed using ELISA. (B–F) WT and Tlr9–/– mice were treated with CXCL13 neutralizing antibodies (10 mg/mouse) or control IgG (10 mg/mouse) immediately after CLP. PLF and plasma were collected at 18 hours after CLP. (B) Peritoneal B-1 cell numbers. (C) Peritoneal IgM levels. (D) Bacterial load in PLF. (E) Plasma IL-6 levels. (F) Seven-day survival. For A–C and E, data are shown as mean ± SD. Symbols represent individual mice. *P < 0.05; **P < 0.01, unpaired, 2-tailed Student’s t tests. For D, symbols represent individual mice. *P < 0.05, nonparametric Mann-Whitney U test. For F, n = 13–19/group as indicated. *P < 0.05 versus Tlr9–/– IgG, log-rank test. (G–K) WT mice were treated with recombinant CXCL13 (10 mg/mouse) or PBS immediately after CLP. (G) Peritoneal B-1 cell number. (H) Peritoneal IgM levels. (I) Bacterial load in PLF. (J) Plasma IL-6 levels. (K) Seven-day survival. For G, H, and J, data are shown as mean ± SD. Symbols represent individual mice. *P < 0.05, unpaired, 2-tailed Student’s t test. For I, symbols represent individual mice. *P < 0.05, nonparametric Mann-Whitney U test. For K, n = 10/group. *P < 0.05, log-rank test.