T cell pathology in skin inflammation

Abstract

Forming the outer body barrier, our skin is permanently exposed to pathogens and environmental hazards. Therefore, skin diseases are among the most common disorders. In many of them, the immune system plays a crucial pathogenetic role. For didactic and therapeutic reasons, classification of such immune-mediated skin diseases according to the underlying dominant immune mechanism rather than to their clinical manifestation appears to be reasonable. Immune-mediated skin diseases may be mediated mainly by T cells, by the humoral immune system, or by uncontrolled unspecific inflammation. According to the involved T cell subpopulation, T cell–mediated diseases may be further subdivided into T1 cell–dominated (e.g., vitiligo), T2 cell–dominated (e.g., acute atopic dermatitis), T17/T22 cell–dominated (e.g., psoriasis), and Treg cell–dominated (e.g., melanoma) responses. Moreover, T cell–dependent and -independent responses may occur simultaneously in selected diseases (e.g., hidradenitis suppurativa). The effector mechanisms of the respective T cell subpopulations determine the molecular changes in the local tissue cells, leading to specific microscopic and macroscopic skin alterations. In this article, we show how the increasing knowledge of the T cell biology has been comprehensively translated into the pathogenetic understanding of respective model skin diseases and, based thereon, has revolutionized their daily clinical management.

Advances in phototherapy for psoriasis and atopic dermatitis

“…Although psoriasis and atopic dermatitis are clinically, histologically, and immunologically distinct diseases, both are characterized by activated T-cell infiltration in the skin that is followed by increased proliferation of keratinocytes resulting in the thickening of the skin. These T-cell mediated diseases differ in skin-infiltrating T-cell subpopulations [4]. In psoriasis, Th17, Th22 cells and type 3 innate lymphoid cells play a crucial role in producing IL-17 and IL-22 and TNFα, whereas IL-23 is the key cytokine responsible for Th17 activation.…”

“…In contrast, atopic dermatitis is characterized by the accumulation of Th2 cells, and their respective cytokine milieu IL-4, IL-13, and IL-31. In chronic atopic dermatitis lesions, Th1 cells-derived IFN-γ and Th22 cells-produced IL-22 might also have relevance [4].…”

Medical Management of Chronic Plaque Psoriasis in the Modern Age

“…Ultraviolets either from the sun or artificial light play a significant role in treating psoriasis mainly by supressing activated T cells, independently on the cell subpopulation involved in the disease [25]. It has been shown that NB-UVB is the most utilized phototherapeutical approach, inducing clinical and histopathological resolution of moderate-to-severe plaque psoriasis by exerting a cytotoxic effect on epidermal T cells [35,36]. This apoptotic effect on T cells depends mostly on the penetration of the NB-UVB within the lesion, penetration that on the one hand depends on the wavelength and on the other the depth of the skin lesion [37].…”

Impact of Avène Thermal Spring Water on immune cells

“…16 These instructive signals shape the Th cell response allowing the generation of effector Th cells adapted to the pathophysiological situation. 17,18 This complex mediator network is fine-tuned, and any dysfunction or impairment can lead to inappropriate or heightened responses resulting in the development of pathologies. Moreover, in addition to infiltrating lymphocytes, the skin houses a large pool of resident and recirculating memory T cells that can be locally reactivated by local APCs (antigen-presenting cells) in the inflamed tissues.…”