CD4+CD25+Foxp3+ Tregs resolve experimental lung injury in mice and are present in humans with acute lung injury
Franco R. D’Alessio, Kenji Tsushima, Neil R. Aggarwal, Erin E. West, Matthew H. Willett, Martin F. Britos, Matthew R. Pipeling, Roy G. Brower, Rubin M. Tuder, John F. McDyer, Landon S. King
Franco R. D’Alessio, Kenji Tsushima, Neil R. Aggarwal, Erin E. West, Matthew H. Willett, Martin F. Britos, Matthew R. Pipeling, Roy G. Brower, Rubin M. Tuder, John F. McDyer, Landon S. King
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Research Article

CD4+CD25+Foxp3+ Tregs resolve experimental lung injury in mice and are present in humans with acute lung injury

Abstract

Acute lung injury (ALI) is characterized by rapid alveolar injury, inflammation, cytokine induction, and neutrophil accumulation. Although early events in the pathogenesis of ALI have been defined, the mechanisms underlying resolution are unknown. As a model of ALI, we administered intratracheal (i.t.) LPS to mice and observed peak lung injury 4 days after the challenge, with resolution by day 10. Numbers of alveolar lymphocytes increased as injury resolved. To examine the role of lymphocytes in this response, lymphocyte-deficient Rag-1–/– and C57BL/6 WT mice were exposed to i.t. LPS. The extent of injury was similar between the groups of mice through day 4, but recovery was markedly impaired in the Rag-1–/– mice. Adoptive transfer studies revealed that infusion of CD4+CD25+Foxp3+ Tregs as late as 24 hours after i.t. LPS normalized resolution in Rag-1–/– mice. Similarly, Treg depletion in WT mice delayed recovery. Treg transfer into i.t. LPS–exposed Rag-1–/– mice also corrected the elevated levels of alveolar proinflammatory cytokines and increased the diminished levels of alveolar TGF-β and neutrophil apoptosis. Mechanistically, Treg-mediated resolution of lung injury was abrogated by TGF-β inhibition. Moreover, BAL of patients with ALI revealed dynamic changes in CD3+CD4+CD25hiCD127loFoxp3+ cells. These results indicate that Tregs modify innate immune responses during resolution of lung injury and suggest potential targets for treating ALI, for which there are no specific therapies currently available.

Authors

Franco R. D’Alessio, Kenji Tsushima, Neil R. Aggarwal, Erin E. West, Matthew H. Willett, Martin F. Britos, Matthew R. Pipeling, Roy G. Brower, Rubin M. Tuder, John F. McDyer, Landon S. King

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Figure 7

Tregs facilitate alveolar neutrophil clearance in vivo and in vitro.

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Tregs facilitate alveolar neutrophil clearance in vivo and in vitro. (A)...
(A) After administration of i.t. LPS and AT of PBS sham treatment or the indicated lymphocyte subtypes, the percentage of neutrophils in the BAL on day 10 was assessed. †P < 0.05 vs. sham. (B) Percent neutrophils in the alveolar compartment of WT mice after receiving isotype or Treg-depleting Abs. †P < 0.05 versus isotype Ab. (C) Percent BAL neutrophils undergoing apoptosis, as assessed by dual labeling with Annexin V and 7-AAD on day 4 after i.t. LPS in WT or Rag-1–/– mice receiving PBS or AT of Tregs or CD4+CD25– cells. (D) WT and Rag-1–/– mice were exposed to i.t. LPS, and on day 1 or day 4, both BAL and ex vivo BAL mixed cultures were performed. Neutrophils and macrophages were cultured in vitro for 6 hours, then media or the indicated lymphocyte subset was added in a 1:10 lymphocyte/macrophage ratio. (E) Neutrophil apoptosis or macrophage phagocytosis was assessed 24 hours after addition of the indicated cells in vitro. *P < 0.05 vs. day-1 Rag-1–/– and media only.