{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n Interleukin‑19 (IL‑19) is a member of the IL‑10 cytokine family that plays multifaceted roles in immune regulation and inflammation. It is produced by activated monocytes and by tissue‐resident cells such as keratinocytes, and its expression is induced in response to proinflammatory stimuli. In vitro, IL‑19 has been shown to promote the production of key inflammatory mediators (for example, IL‑6 and TNF‑α) while also modulating T‐cell responses by favoring Th2‐type cytokine production (increased IL‑4 and IL‑5), suggesting that IL‑19 can skew the balance of adaptive immunity ["}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": "]. In the respiratory tract, IL‑19 is up‐regulated in bronchial epithelial cells – a response that can be triggered by adenosine receptor activation – and its increased release has been linked to further activation of innate immune cells via TNF‑α production ["}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": "]. In skin, IL‑19 is highly expressed in psoriatic lesions, where it not only marks disease activity but also amplifies IL‑17–driven signals in keratinocytes, leading to enhanced production of antimicrobial peptides and chemokines that contribute to the chronic inflammatory milieu ["}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": "]. In contrast, animal models of inflammatory bowel disease and chronic recurrent multifocal osteomyelitis have revealed a protective, anti‐inflammatory facet of IL‑19; deficiency in IL‑19 is associated with increased production of proinflammatory cytokines and enhanced inflammasome activation ["}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": "]. Moreover, genetic studies have implicated IL‑19 as a candidate gene in type 1 diabetes, underscoring its potential relevance in systemic autoimmune conditions ["}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": "]. Collectively, these findings highlight IL‑19 as a key immunomodulatory cytokine with diverse roles that include both the amplification of local inflammatory responses (in skin and lung) and the limitation of excessive inflammation in other tissues, making it a promising biomarker and potential therapeutic target in a range of inflammatory diseases.\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Yuan-Chun Liao, Wei-Guang Liang, Feng-Wei Chen, et al. 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