ReviewT cell responses in psoriasis and psoriatic arthritis
Section snippets
Psoriasis and psoriatic arthritis clinical features
Psoriasis is a chronic inflammatory skin disease affecting approximately 2%–4% of the population worldwide and is considered the most prevalent immune-mediated disease in humans. [1]. Plaque psoriasis, also known as psoriasis vulgaris, is the commonest form of the disease, representing almost 90% of psoriatic patients [2]. The lesions are characterized by erythematous dry, sharply demarcated plaques with loosely adherent silvery white scalest. The disease appears in other different clinical
Pathogenesis of psoriasis and psoriatic arthritis
An important distinction has been recently made in psoriasis natural history by identifying 2 phases: an initiation phase that starts inflammation and a maintenance phase that perpetuates the inflammatory state [23]. This conceptual distinction can help to divide the cellular and molecular events that determine triggering of the disease from those that are the results of the self-perpetuating cycle and represent downstream effector arms of the inflammatory process.
Psoriasis lesions are
Antigen-specific responses in psoriasis and psoriatic arthritis
The question of antigen specificity of T cell responses in psoriasis and psoriatic arthritis is still unanswered and is strongly linked the autoimmune nature of the disease [53].
An association between streptococcal throat infection and the acute guttate form of psoriasis (an early onset form) has been demonstrated in many studies, and the reported incidence of streptococcal infections preceding this type of psoriasis ranges between 56% and 97% [5].
Chronic plaque psoriasis is also exacerbated
Concluding remarks
The triggering event of the initial phase of the disease is unclear as the autoimmune etiology of psoriasis is unclear. By integrating information on recent advances on Th17/Th1 γδT cell contribution in determining inflammation on psoriatic skin together with early data on keratin cross-reactive CD8 T cells with specificity for streptococcal antigens, we have highlighted the role of the different subpopulations of T cells in psoriasis and psoriatic arthritis and hypothesized a hierarchical role
Take-home messages
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Keratin cross-reactive CD8 T cells with specificity for microbial antigens can represent the core autoimmune mechanism of psoriasis pathogenesis.
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Th17 T cells and γδ T cells act as downstream effectors stimulated by common-antigens or bystander activation
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Th17 driven inflammatory cycle can lead to the main clinical manifestations in the skin and extend inflammation to the joint.
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Dendritic cells in genetically predisposed individuals could cross-present self-epitopes leading to epitope spreading in
Acknowledgments
We thank Prof. Giuseppe Banfi, I.R.C.C.S. Istituto Ortopedico Galeazzi, Milan (Italy); Dr. Daniela Talarico, S. Raffaele Research Hospital, Milan (Italy) and Prof. Riccardo Gavioli, University of Ferrara, Ferrara (Italy) for critical reading of the manuscript. This work received support from National Psoriasis Foundation.
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