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 7

CTLA4 blockade decreases the accumulation of p16INK4a-expressing cells in vivo and mediates killing of senescent cells ex vivo.

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CTLA4 blockade decreases the accumulation of p16INK4a-expressing cells i...
(A and B) Immunohistochemistry staining of p16INK4a in lung tissue sections from the 2 groups receiving either IgG1 isotype control or ipilimumab. Scale bar: 800 μm (left); 30 μm (right). (C) Quantitation of p16INK4a+ cells observed in high-power field (hpf) images of the IgG1 isotype control and ipilimumab (n = 4 in each group). (D) Schematic representation of ex vivo studies of CD8+ T cell–mediated killing. (E) Lung cells isolated from bleomycin-injured mice were stained with SPiDER-β-GAL and cocultured with CD8+ T cells (2:1 ratio) isolated from the same mice for 12 hours with or without ipilimumab (0.05 μg/mL). Real-time detection of fluorescent area of β-GAL+ cells/image (n = 16 images per condition at each time point indicated). (F) Images of CD8+ T cell–mediated killing of β-GAL+ lung cells. Images were taken using live-cell imaging with the IncuCyte system. The CD8+ T cells were labeled with Cellbright 640 (Biotium) (red) to visualize their interaction with β-GAL+ (green) lung cells. Data are shown as mean ± SEM. Statistical differences in C were tested using a paired 2-tailed Student’s t test.