title: TH9 cells in skin disorders.
abstract: Interleukin 9 secreting TH9 cells have been proposed as the latest addition to the family of T helper cell subsets. While a growing body of evidence from animal models points to important roles for these cells in allergic inflammation of the lung, autoinflammation of the gastrointestinal tract, and tumor immunity, their role in skin immunity and skin immunopathology remains poorly defined. Interestingly, studies of T helper cells from healthy humans suggest that TH9 cells are predominantly skin-homing and skin-resident and that they are involved in protection against extracellular pathogens. Thus, TH9 cells have entered the stage as potential mediators of cutaneous pathology. However, under which conditions and by which mechanisms these cells contribute to skin immunity and disease still has to be investigated. Here, we review our current understanding of TH9 cells as skin-tropic T helper cells and their involvement in skin pathology. Further, we discuss open questions with regard to the intricate nature of interleukin 9 producing T helper cells.
authors.affiliation: Department of Dermatology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Rachael A
authors.initials: RA
authors.lastname: Clark
authors.affiliation: Department of Dermatology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland. Christoph.Schlapbach@insel.ch.
authors.forename: Christoph
authors.initials: C
authors.lastname: Schlapbach
mesh_terms: D056704:Adaptive Immunity; D000485:Allergens / Q000276:immunology; D000818:Animals; D005786:Gene Expression Regulation; D006801:Humans; D007113:Immunity, Innate; D007167:Immunotherapy; D016906:Interleukin-9 / Q000235:genetics / Q000378:metabolism*; D008213:Lymphocyte Activation; D015398:Signal Transduction; D012871:Skin Diseases / Q000209:etiology* / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000378:metabolism*
chemical_list: D000485:Allergens; D016906:Interleukin-9
keywords: Allergic contact dermatitis; Atopic dermatitis; Candida albicans; Cutaneous; Cutaneous T cell lymphoma; IL-9; Inflammation; Interleukin 9; Psoriasis; Skin; Skin homing; Skin resident; T helper cell subsets; T helper cells; T helper type 9 cells; Th9 cells