Reactivation of CTLA4-expressing T cells accelerates resolution of lung fibrosis in a humanized mouse model
Santosh Yadav, Muralidharan Anbalagan, Shamima Khatun, Devadharshini Prabhakaran, Yasuka Matsunaga, Justin Manges, James B. McLachlan, Joseph A. Lasky, Jay Kolls, Victor J. Thannickal
Santosh Yadav, Muralidharan Anbalagan, Shamima Khatun, Devadharshini Prabhakaran, Yasuka Matsunaga, Justin Manges, James B. McLachlan, Joseph A. Lasky, Jay Kolls, Victor J. Thannickal
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Research Article Immunology Pulmonology

Reactivation of CTLA4-expressing T cells accelerates resolution of lung fibrosis in a humanized mouse model

Abstract

Tissue regenerative responses involve complex interactions between resident structural and immune cells. Recent reports indicate that accumulation of senescent cells during injury repair contributes to pathological tissue fibrosis. Using tissue-based spatial transcriptomics and proteomics, we identified upregulation of the immune checkpoint protein, cytotoxic T lymphocyte–associated protein 4 (CTLA4), on CD8+ T cells adjacent to regions of active fibrogenesis in human idiopathic pulmonary fibrosis and in a repetitive bleomycin lung injury murine model of persistent fibrosis. In humanized CTLA4-knockin mice, treatment with ipilimumab, an FDA-approved drug that targets CTLA4, resulted in accelerated lung epithelial regeneration and diminished fibrosis from repetitive bleomycin injury. Ipilimumab treatment resulted in the expansion of Cd3e+ T cells, diminished accumulation of senescent cells, and robust expansion of type 2 alveolar epithelial cells, facultative progenitor cells of the alveolar epithelium. Ex vivo activation of isolated CTLA4-expressing CD8+ cells from mice with established fibrosis resulted in enhanced cytolysis of senescent cells, suggesting that impaired immune-mediated clearance of these cells contributes to persistence of lung fibrosis in this murine model. Our studies support the concept that endogenous immune surveillance of senescent cells may be essential in promoting tissue regenerative responses that facilitate the resolution of fibrosis.

Authors

Santosh Yadav, Muralidharan Anbalagan, Shamima Khatun, Devadharshini Prabhakaran, Yasuka Matsunaga, Justin Manges, James B. McLachlan, Joseph A. Lasky, Jay Kolls, Victor J. Thannickal

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Figure 5

Fibrosis resolution in mice with CTLA4 blockade is associated with activation of T cell subsets and expansion of alveolar type 2 cells.

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Fibrosis resolution in mice with CTLA4 blockade is associated with activ...
(A) Experimental outline of humanized CTLA4 mice subjected to repetitive bleomycin injury–induced pulmonary fibrosis via oropharyngeal administration of bleomycin (1.25 U per kg body weight) in 2 doses,14 days apart. On day 21 after the second dose, mice were treated intraperitoneally with either control IgG1 isotype or the anti-CTLA4 monoclonal antibody ipilimumab at doses of 5 mg per kg body weight twice per week for 4.5 weeks (total of 9 doses). (B and C) UMAP of whole-lung cells from the IgG1 isotype control and ipilimumab groups. Cell clusters identified by scRNA-Seq are colored by cell type. The UMAP indicating the sftpa1+ cell cluster is highlighted with a hexagon. (D) Volcano plot showing differential gene expression in T cell clusters of the scRNA-Seq IgG1 isotype control and ipilimumab dataset. A total of 99 differentially expressed genes were identified [log2(fold change) > 0.3 and FDR-adjusted P < 0.05]. (E) Violin plot showing gene expression of Icos in the Cd3δ+ and Cd3ε+ T cell clusters of the scRNA-Seq data for whole lung cells from the IgG1 isotype control or ipilimumab groups. (F) Volcano plot showing differential gene expression in the sftpa1+ cell cluster of the scRNA-Seq dataset for the IgG1 isotype control and ipilimumab groups. A total of 399 differentially expressed genes were identified [log2(fold change) > 0.3, FDR-adjusted P < 0.05]. (G–I) Violin plots showing AT2 cell expression of the marker genes sftpb, sftpc, and sftpd in the in sftpa1+ cell cluster.