title: Foxp3+ regulatory T cells of psoriasis patients easily differentiate into IL-17A-producing cells and are found in lesional skin.
abstract: Psoriasis is an autoimmune-related chronic inflammatory skin disease that is strongly associated with IL-23 and T helper-17 (Th17) effector cytokines. In addition, CD4+CD25(high) regulatory T-cell (Treg) function appeared to be impaired in psoriasis. CD4+CD25(high)Foxp3+ Tregs are typically considered inhibitors of autoimmune responses. However, under proinflammatory conditions, Tregs can differentiate into inflammation-associated Th17 cells--a paradigm shift, with as yet largely unknown consequences for human disease initiation or progression. Th17 cells are highly proinflammatory T cells that are characterized by IL-17A and IL-22 production and expression of the transcription factor retinoic acid-related orphan receptor γt (RORγt). We here show that Tregs of patients with severe psoriasis, as compared with those of healthy controls, have an enhanced propensity to differentiate into IL-17A-producing cells on ex vivo stimulation. This enhanced Treg differentiation was linked to unexpectedly high RORγt levels and enhanced loss of Foxp3. Notably, IL-23 boosted this Treg differentiation process particularly in patients with psoriasis but less so in controls. IL-23 further reduced Foxp3 expression while leaving the high RORγt levels unaffected. The histone/protein deacetylase inhibitor, Trichostatin-A, prevented Th17 differentiation of Tregs in psoriasis patients. Importantly, IL-17A+/Foxp3+/CD4+ triple-positive cells were present in skin lesions of patients with severe psoriasis. These data stress the clinical relevance of Treg differentiation for the perpetuation of chronic inflammatory disease and may pave novel ways for immunotherapy.
authors.affiliation: Department of Dermatology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: H Jorn
authors.initials: HJ
authors.lastname: Bovenschen
authors.forename: Peter C
authors.initials: PC
authors.lastname: van de Kerkhof
authors.forename: Piet E
authors.initials: PE
authors.lastname: van Erp
authors.forename: Rob
authors.initials: R
authors.lastname: Woestenenk
authors.forename: Irma
authors.initials: I
authors.lastname: Joosten
authors.forename: Hans J P M
authors.initials: HJ
authors.lastname: Koenen
mesh_terms: D001706:Biopsy; D015704:CD4 Antigens / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D020405:Dermis / Q000276:immunology / Q000473:pathology; D005434:Flow Cytometry; D051858:Forkhead Transcription Factors / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D020381:Interleukin-17 / Q000276:immunology* / Q000378:metabolism; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D053759:Interleukin-23 / Q000378:metabolism / Q000494:pharmacology; D057132:Nuclear Receptor Subfamily 1, Group F, Member 3 / Q000378:metabolism; D011565:Psoriasis / Q000276:immunology* / Q000473:pathology*; D012720:Severity of Illness Index; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D058504:Th17 Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism
chemical_list: D015704:CD4 Antigens; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; C508717:IL17A protein, human; C508017:IL2RA protein, human; D020381:Interleukin-17; D053645:Interleukin-2 Receptor alpha Subunit; D053759:Interleukin-23; D057132:Nuclear Receptor Subfamily 1, Group F, Member 3; C539900:RORC protein, human