REVIEWRegulatory T-cells in asthmaHarb, Hania; Chatila, Talal A.b Author Information aInstitute for Medical Microbiology and Virology, University Hospital Dresden, Technical University Dresden, Germany bDivision of Immunology, Boston Children's Hospital, Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA Correspondence to Hani Harb, Institute for Medical Microbiology and Virology, University Hospital Dresden, Technical University Dresden, Fiedlerstr. 47, 01307 Dresden, Germany. E-mail: [email protected] and Talal A. Chatila, Division of Immunology, Boston Children's Hospital, Department of Pediatrics, Harvard Medical School, I Blackfan Circle, Boston, MA 02115, USA. E-mail: [email protected] Current Opinion in Allergy and Clinical Immunology ():10.1097/ACI.0000000000000887, January 05, 2023. | DOI: 10.1097/ACI.0000000000000887 Buy PAP Metrics Abstract Purpose of the Review This review addresses recent progress in our understanding of the role of regulatory T (Treg) cells in enforcing immune tolerance and tissue homeostasis in the lung at steady state and in directing the immune response in asthmatic lung inflammation. Recent findings Regulatory T cells regulate the innate and adaptive immune responses at steady state to enforce immune tolerance in lung tissues at steady state and their control of the allergic inflammatory responses induced by allergens. This regulatory function can break down in the context of chronic asthmatic airway inflammation such that the lung tissue Treg cells become skewed towards a pathogenic phenotype that aggravates and perpetuates disease. Subversion of lung tissue Treg cell function involves their upregulation of Notch4 expression, which in turn acts to amplify T helper type 2 and type 17 and innate lymphoid cell type 2 responses in the airways. Summary A dual role for Treg cells has emerged both as immune regulators but also a potential disease effectors in asthma, with implications for disease therapy. Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.