ITK Deficiency Attenuates Alveolar Hemorrhage by Enhancing Regulatory T Cell-Mediated Tissue Resilience
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eLife Assessment
This study investigates the role of Interleukin-2-inducible T cell kinase (ITK) deficiency in autoimmune lung injury using a pristane-induced pulmonary hemorrhage (PH) model, suggesting that ITK-deficient regulatory T cells (Tregs) restrict severe tissue pathology. The work represents a valuable addition to the fields of autoimmunity, inflammation, and T-cell biology in the lung. However, the experimental evidence supporting the underlying cellular and molecular mechanisms and the integration of foundational background literature to provide the necessary context are incomplete.
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Abstract
Pulmonary hemorrhage (PH) is a life-threatening manifestation of systemic autoimmunity characterized by immune-mediated disruption of the alveolar-capillary barrier. Despite mortality rates exceeding 50%, the molecular checkpoints that govern the transition from destructive inflammation to protective immune regulation remain poorly defined. Building on our discovery that interleukin-2-inducible T cell kinase (ITK) uncouples pathogenic inflammation from protective immunity, we investigated ITK as a central regulator of autoimmune lung injury. Using the pristane-induced PH model, we show that ITK deficiency confers near-complete protection against PH and associated multi-organ injury. This protection is accompanied by marked remodeling of the T cell compartment, including expansion of CD44⁺CD122⁺Eomes⁺T-bet⁺ memory-like subsets and significant enrichment of Foxp3⁺ regulatory T cells (Tregs). Notably, adoptive transfer of ITK-deficient Tregs was sufficient to rescue PH and suppress systemic proinflammatory cytokine production in wild-type recipients, identifying these cells as key mediators of tissue protection. Transcriptomic profiling further revealed that loss of ITK signaling reprograms Tregs toward a metabolically and functionally enhanced state, with enrichment of oxidative phosphorylation (OXPHOS), mTORC1, STAT5 signaling, and tissue-repair-associated programs. Together, these findings identify ITK as a critical regulator of the balance between pulmonary injury and reparative immunity and provide a mechanistic rationale for targeting the ITK axis in severe inflammatory lung disease.
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eLife Assessment
This study investigates the role of Interleukin-2-inducible T cell kinase (ITK) deficiency in autoimmune lung injury using a pristane-induced pulmonary hemorrhage (PH) model, suggesting that ITK-deficient regulatory T cells (Tregs) restrict severe tissue pathology. The work represents a valuable addition to the fields of autoimmunity, inflammation, and T-cell biology in the lung. However, the experimental evidence supporting the underlying cellular and molecular mechanisms and the integration of foundational background literature to provide the necessary context are incomplete.
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Reviewer #1 (Public review):
In this study, Hossain et al. investigated the role of Interleukin-2-inducible T cell kinase (ITK) in autoimmune lung injury, demonstrating that ITK-deficient (Itk-/-) mice are protected against pristane-induced pulmonary hemorrhage (PH). The authors suggest that this protection correlates with a significant remodeling of the T cell compartment in Itk-/- mice, including increased frequency of memory-like CD4+ and CD8+ T cells (CD44⁺CD62L⁺) as well as higher frequency of Treg populations. Furthermore, adoptive transfer of ITK-deficient Treg isolated from injured ITK-deficient mice confers protection against pulmonary hemorrhage in WT recipients.
Strengths:
The adoptive transfer of wild-type and Itk-/- Treg populations demonstrates that ITK-deficient Treg can actively rescue pre-existing lung injury and …
Reviewer #1 (Public review):
In this study, Hossain et al. investigated the role of Interleukin-2-inducible T cell kinase (ITK) in autoimmune lung injury, demonstrating that ITK-deficient (Itk-/-) mice are protected against pristane-induced pulmonary hemorrhage (PH). The authors suggest that this protection correlates with a significant remodeling of the T cell compartment in Itk-/- mice, including increased frequency of memory-like CD4+ and CD8+ T cells (CD44⁺CD62L⁺) as well as higher frequency of Treg populations. Furthermore, adoptive transfer of ITK-deficient Treg isolated from injured ITK-deficient mice confers protection against pulmonary hemorrhage in WT recipients.
Strengths:
The adoptive transfer of wild-type and Itk-/- Treg populations demonstrates that ITK-deficient Treg can actively rescue pre-existing lung injury and reverse systemic secondary metrics like proteinuria in wild-type recipients, providing proof-of-concept validation for the therapeutic utility of the ITK-Treg axis.
Weaknesses:
A primary limitation of this manuscript is its omission of foundational literature from the Schwartzberg and Littman laboratories, which originally established the indispensable role of IL-2-inducible T-cell kinase (ITK) in proximal T-cell receptor (TCR) signaling dynamics and thymic lineage commitment. Because classic studies demonstrate that ITK is a critical regulator of thymic T cell development and cellular proliferation (PMID: 8777721, 10213685), the authors' claim that "these findings indicate that ITK deficiency skews the T cell compartment toward a memory-like state, establishing a distinct immune baseline that may favor protective and regulatory responses over pathogenic inflammation" is not substantiated by evidence and requires more robust validation.
The exclusive reliance on splenic immunophenotyping is a major limitation, as it fails to capture the local cellular dynamics within the primary organs of injury (the lung and kidney). Evaluating canonical and non-canonical Treg expansion solely in the spleen overlooks the distinct functional programming of tissue-resident subsets. The authors should extend their characterization of regulatory T cell compartments directly to the lungs and draining lymphoid structures.
More importantly, the authors overlook key historical publications that explicitly established ITK as a negative "rheostat" or gatekeeper for regulatory T cell (Treg) differentiation. Specifically, Huang et al. (PMID: 25063868) previously demonstrated that Treg abundance is inversely correlated with ITK expression, and that ITK activity serves as a vital negative tuner of IL-2-driven Foxp3⁺ Treg expansion. Since it is already well-established that suppressing or deleting ITK promotes Treg accumulation and function, and that these cells are intrinsically vital to suppressing systemic autoimmunity, it is unclear how these findings expand upon our existing mechanistic understanding of ITK regulatory biology.
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Reviewer #2 (Public review):
Summary:
In this manuscript, Hossaim and colleagues investigate the role of the ITK kinase in modulating inflammation in a pristane-induced lung hemorrhage model. Using a germline ITK KO mouse, they report that loss of ITK skews the T cell compartment toward a memory-like state, expanding Tregs, and conferring protection against alveolar hemorrhage, inflammatory monocyte recruitment, proteinuria, and systemic cytokine elevation. They further show that transfer of ITK-deficient Tregs into wild-type hosts with established disease attenuates injury and shifts the cytokine balance toward resolution, and that ITK-deficient Tregs carry a transcriptional signature enriched for OXPHOS, mTORC1, MYC, and cell-cycle programs. While these observations are interesting for the development of potential immunotherapies, …
Reviewer #2 (Public review):
Summary:
In this manuscript, Hossaim and colleagues investigate the role of the ITK kinase in modulating inflammation in a pristane-induced lung hemorrhage model. Using a germline ITK KO mouse, they report that loss of ITK skews the T cell compartment toward a memory-like state, expanding Tregs, and conferring protection against alveolar hemorrhage, inflammatory monocyte recruitment, proteinuria, and systemic cytokine elevation. They further show that transfer of ITK-deficient Tregs into wild-type hosts with established disease attenuates injury and shifts the cytokine balance toward resolution, and that ITK-deficient Tregs carry a transcriptional signature enriched for OXPHOS, mTORC1, MYC, and cell-cycle programs. While these observations are interesting for the development of potential immunotherapies, there are several issues with the methodological approach that support the authors' claims, tempering my enthusiasm for this manuscript.
Strengths:
(1) The clinical motivation and potential targeted therapies are relevant.
(2) The murine phenotype seems robust.
Weaknesses:
(1) All loss-of-function experiments are from a global ITK knockout. This is a major limitation and weakness of this study. The protection observed in the intact knockout, therefore, cannot be attributed to Tregs specifically. The Treg-intrinsic claim rests almost entirely on a single adoptive-transfer experiment. In order to show that this effect is Treg-specific, the authors would need to generate a Treg-specific ITK-deficient mouse
(2) In their sufficiency experiment (adoptive Treg cell transfer), donor and/or host cells are not congenically marked, so persistence, lung trafficking, and in vivo expansion of transferred Tregs are not demonstrated.
(3) The authors claim that ITK-deficient Tregs possess enhanced metabolic fitness. This conclusion is based on transcriptional profiling of isolated splenic Tregs from unchallenged mice, yet it concerns lung protection during active disease. A disease-state and ideally lung-relevant transcriptome would more directly support the mechanistic narrative. Additional functional validation would be needed (Seahorse assay, mitochondrial mass/potential, etc). Some of these GSEA programs enriched in ITK-deficient Tregs could reflect a more general proliferative signature.
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Reviewer #3 (Public review):
Summary:
Hossain et al. investigate the role of ITK as a central regulator of autoimmune lung injury. They used ITK-deficient mice and the pristane-induced pulmonary hemorrhage (PH) model to show that ITK deficiency confers protection against PH. The adoptive cell transfer experiment suggests a possible role for altered Treg cells in ITK-deficient mice in regulating the inflammatory response in the lungs of pristane-injected mice. This study shows that targeting the ITK axis may be beneficial by reducing systemic inflammatory injury that contributes to poor outcomes in PH.
Strengths:
This study highlights the importance of ITK in regulating pulmonary hemorrhage. The enrichment of Treg cells is known to confer protection in autoimmunity-mediated alveolar damage. However, ITK's involvement in regulating Treg …
Reviewer #3 (Public review):
Summary:
Hossain et al. investigate the role of ITK as a central regulator of autoimmune lung injury. They used ITK-deficient mice and the pristane-induced pulmonary hemorrhage (PH) model to show that ITK deficiency confers protection against PH. The adoptive cell transfer experiment suggests a possible role for altered Treg cells in ITK-deficient mice in regulating the inflammatory response in the lungs of pristane-injected mice. This study shows that targeting the ITK axis may be beneficial by reducing systemic inflammatory injury that contributes to poor outcomes in PH.
Strengths:
This study highlights the importance of ITK in regulating pulmonary hemorrhage. The enrichment of Treg cells is known to confer protection in autoimmunity-mediated alveolar damage. However, ITK's involvement in regulating Treg cell function is interesting and could be explored as a novel therapeutic approach for chronic inflammation.
Weaknesses:
The novelty of this study lies in the association between ITK-deficient Tregs and pulmonary hemorrhage in autoimmunity. The weakness of the manuscript is the lack of sufficient experiments to support the claim that ITK-deficient mice show protection specifically mediated by Treg cells, and to demonstrate that ITK-deficient Treg cells are more efficient than WT Treg cells in regulating other immune cells that drive pulmonary damage. The authors performed all the experiments in ITK global knockout mice, in which not only T cells but all other cell types are deficient in ITK. Furthermore, they have not performed any functional analysis to demonstrate the functional differences between WT Treg and ITK-deficient Treg cells, undermining the novelty of this study.
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