ITK deficiency protects against autoimmune pulmonary hemorrhage by promoting Amphiregulin-producing regulatory T cells

Pulmonary hemorrhage (PH) is a life-threatening manifestation of systemic autoimmunity caused by immune-mediated disruption of the alveolar capillary barrier. Despite high mortality, the molecular checkpoints that shift destructive inflammation toward protective immune regulation remain poorly defined. Here, using the pristane-induced PH model, we identify interleukin-2-inducible T cell kinase (ITK) as a critical regulator of autoimmune lung injury. ITK deficiency (Itk⁻/⁻) conferred near-complete protection from PH and associated multiorgan injury, accompanied by reduced proinflammatory monocytes and neutrophils and increased Foxp3⁺ regulatory T cells (Tregs). Adoptive transfer of Itk⁻/⁻ Tregs protected wild-type recipients from PH and suppressed systemic proinflammatory cytokines, identifying Tregs as key mediators of tissue protection. Mechanistically, lung Itk⁻/⁻Tregs exhibited increased amphiregulin, a mediator of tissue repair. Transcriptomic profiling further showed that ITK loss reprogrammed Tregs toward a metabolically and functionally enhanced state, with enrichment of oxidative phosphorylation, mTORC1 and STAT5 signaling, and tissue-repair programs. These findings establish ITK as a regulator of the balance between pulmonary injury and reparative immunity and support targeting the ITK axis in severe inflammatory lung disease.