title: T cell responses in psoriasis and psoriatic arthritis.
abstract: According to the current view the histological features of psoriasis arise as a consequence of the interplay between T cells, dendritic cells and keratinocytes giving rise to a self-perpetuating loop that amplifies and sustains inflammation in lesional skin. In particular, myeloid dendritic cell secretion of IL-23 and IL-12 activates IL-17-producing T cells, Th22 and Th1 cells, leading to the production of inflammatory cytokines such as IL-17, IFN-γ, TNF and IL-22. These cytokines mediate effects on keratinocytes thus establishing the inflammatory loop. Unlike psoriasis the immunopathogenic features of psoriatic arthritis are poorly characterized and there is a gap in the knowledge of the pathogenic link between inflammatory T cell responses arising in the skin and the development of joint inflammation. Here we review the knowledge accumulated over the years from the early evidence of autoreactive CD8 T cells that was studied mainly in the years 1990s and 2000s to the recent findings of the role of Th17, Tc17 cells and γδ T cells in psoriatic disease pathogenesis. The review will also focus on common and distinguishing features of T cell responses in psoriatic plaques and in synovial fluid of patients with psoriatic arthritis. The integration of this information could help to distinguish the role played by T cells in the initiation phase of the disease from the role of T cells as downstream effectors sustaining inflammation in psoriatic plaques and potentially leading to disease manifestation in distant joints.
authors.affiliation: I.R.C.C.S Istituto Ortopedico Galeazzi, Department of Dermatology and Venereology, Milan, Italy; University of Milan, Milan, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Diani
authors.affiliation: I.R.C.C.S Istituto Ortopedico Galeazzi, Department of Dermatology and Venereology, Milan, Italy; University of Milan, Milan, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Altomare
authors.affiliation: I.R.C.C.S Istituto Ortopedico Galeazzi, Laboratory of Translational Immunology, Milan, Italy. Electronic address: eva.reali@grupposandonato.it.
authors.forename: Eva
authors.initials: E
authors.lastname: Reali
mesh_terms: D015535:Arthritis, Psoriatic / Q000235:genetics / Q000276:immunology* / Q000473:pathology*; D015551:Autoimmunity; D018414:CD8-Positive T-Lymphocytes / Q000473:pathology; D016207:Cytokines / Q000276:immunology; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000473:pathology; D015603:Keratinocytes / Q000473:pathology; D011565:Psoriasis / Q000235:genetics / Q000276:immunology* / Q000473:pathology*; D012867:Skin / Q000473:pathology
chemical_list: D016207:Cytokines
keywords: Antigen-specific T cells; Psoriasis/psoriatic arthritis/genetics; Psoriasis/psoriatic arthritis/immunology/autoimmunity; Psoriasis/psoriatic arthritis/inflammation; Psoriasis/psoriatic arthritis/pathogenesis; Self-antigen cross-presentation