Clinical trials successfully using antibodies targeting IL-17 in psoriasis support the importance of IL-17 in the pathophysiology of this disease. However, there is a debate concerning the source and dynamics of IL-17 production in inflamed skin. Here we characterized IL-17-producing immune cells over time, using two established in vivo models of human skin inflammation that share many histological features with psoriasis, i.e., leukotriene B4 application and tape-stripping. Both treatments revealed a clear influx of neutrophils and T cells. Staining for IL-17 revealed that the majority of IL-17 was expressed by neutrophils and mast cells, in both models. Neutrophils, but not mast cells, coexpressed the IL-17-associated transcription factor RORγt and were able to form extracellular traps. While the presence of mast cells remained steady during the skin inflammatory process, the presence of neutrophils was clearly dynamic in time. Therefore, it is attractive to hypothesize that IL-17+/RORγt+ neutrophils contribute to human skin inflammation in vivo and possibly to the pathogenesis of skin diseases such as psoriasis. Surprisingly, T cells represented a minority of the IL-17-expressing cell population. These observations challenge the classical opinion that IL-17 is predominantly associated with T cells in skin inflammation.

The TOPCam is the first noninvasive technique to visualize the microcirculation of psoriatic lesions in a whole field, to correct images for the heartbeat, and to reveal heterogeneity in perfusion intensity.

Background: In healthy skin, tape stripping induces a transient wave of histological changes resembling immune-mediated skin diseases, such as psoriasis. The response to surface trauma may harbor mechanisms which are also relevant to the development of Koebner-positive skin disorders. However, studies on newly discovered drivers of inflammation in regenerative skin are lacking. Methods: The course of epidermal proliferation and keratinization as well as key representatives of innate and acquired immunity were studied during the first 72 h after tape stripping. Results: Epidermal rupture rapidly activates various epidermal processes, which remain upregulated for 72 h. Elastase+ and IL-17+ cells dominate the acute phase and their numbers decrease rapidly thereafter. The number of T-Bet+ cells increases more gradually, reaching maximum levels several hours later when the other cell types decrease. Conclusions: This model permits investigations on the sequence of crucial inflammatory processes set off by cutaneous injury, which are presumed to play a role within the pathogenesis of immune-mediated skin diseases exhibiting the Koebner phenomenon.

The Ehlers-Danlos syndrome (EDS) is a clinically and genetically heterogeneous group of inherited connective tissue disorders. The six major, well-defined, subtypes are classified according to diagnostic criteria, formalized in the Villefranche revised nosology. Shortly after the publication of these criteria in 1998, a further distinct type of EDS, the tenascin-X (TNX)-deficient type EDS, was reported. The phenotype of this largely unknown type of EDS resembles the phenotype of the classical type of EDS, but its inheritance is autosomal recessive and wound healing is normal; hence, no atrophic scars are present. The clinical diagnosis can be confirmed by the absence of TNX in the serum and by mutation analysis of the TNXB gene. Because the TNX-deficient type EDS is rare and not included in the current diagnostic criteria, this diagnosis is often delayed or even overlooked. Here, we describe four cases which improve the clinical recognition of this type of EDS.

Summary Background The use of recently introduced biologics targeting specific immune mechanisms has identified crucial steps in the pathogenesis of psoriasis. Studying the dynamics of changes of these target mechanisms in sequential skin biopsies during treatment with biologics may reveal potential biomarkers. Correlation between clinical parameters and the expression of specific genes during treatments may identify markers indicative of treatment response. Objectives This observational open‐label study aimed to provide an overview of important cell biological changes in lesional skin during treatment with adalimumab, and their relationship to clinical improvement. Methods Ten patients with moderate‐to‐severe plaque psoriasis were included and treated with adalimumab for 16 weeks. At baseline, and after 10 days and 16 weeks of treatment clinical scores were assessed and biopsies were taken to examine gene expression at the mRNA and protein level. Results The expression of marker genes for innate immunity, and epidermal differentiation and proliferation was rapidly restored to normal levels, whereas genes of the adaptive immune system showed a delayed decrease. The static and dynamic course of CD1a+ Langerhans cells and Ki67+ nuclei showed a significant strong correlation to the Psoriasis Area and Severity Index score. No correlation between interleukin‐17 expression and clinical scores was found. Conclusions The innate immune system is affected during adalimumab treatment well before the changes in the adaptive immune system become apparent. We may speculate that the addition of a treatment with an early effect on adaptive immunity to adalimumab may result in superior effectiveness compared with monotherapies.

Background: Research has revealed new insights into the pathogenesis of psoriasis, leading to new therapeutic options. So far the order of changes in the pathogenesis of psoriasis is unclear. The responses to cutaneous leukotriene B₄ (LTB₄) application have been studied in the past as an in vivo model for inflammation. The aim of the present study is to find out the order of changes of key steps in inflammation, which all have been shown to be involved in mature psoriatic lesions. Objective: To study the dynamics of the consecutive stages of inflammation in challenged skin as a reflection of a psoriasis-like inflammatory response. Methods: We examined the dynamics of epidermal growth control and the key representatives of the innate and acquired immune system during the first 72 h after challenging the skin by LTB₄ application. Results: Interleukin 17-positive (IL-17+) cells dominate the acute phase of inflammation, whereas T-Bet+ cells seem to increase gradually during the entire observation period. This indicates a more important role for IL-17 in the unstable phase of inflammation and a more prominent role for T-Bet+ cells within the chronic phase. Conclusion: The present model is highly reproducible and is useful in studying the dynamics of a psoriasis-like inflammation with respect to key components of immunity. It could provide a useful tool to study the immediate biological effects of new therapies like anti-IL-17 drugs on IL-17 production and effects on cutaneous inflammation and epidermal proliferation in vivo.

In the skin of good-responders the expression of dermal CD31(+) endothelium remains significantly elevated within the treated lesions compared with the distant uninvolved skin, whereas a marked reduction in the perfusion intensity and SUM score was found. This indicates that clinical improvement might outrun endothelial changes.

Diminished suppressive capacity of regulatory T cells (Treg) has been demonstrated in blood and in lesional skin of psoriatic patients. Treatment with anti-TNFa restored the number and function of circulating Treg in psoriasis. We aimed to study Treg in the skin of psoriatic patients undergoing topical treatment with calcipotriol-betamethasone dipropionate (CBD) ointment (n = 12) or systemic treatment with anti-TNFa agent adalimumab (n = 10). Skin biopsies were collected from patients with chronic plaque psoriasis who responded to the above-mentioned treatments with a SUM-score improvement of at least 50% (at the end of treatment). Biopsies were processed for immunohistochemistry. As Treg function is associated with a numerical balance between Treg and effector T cells, Foxp3/CD4 ratios were calculated. It appeared that both treatments cause a significant decrease in the presence of Foxp3+ cells. However, in patients that were treated with CBD ointment, we observed lower Foxp3/CD4 ratios after 8 weeks of treatment compared to baseline (t = 0: 0.41 AE 0.08; t = 8: 0.22 AE 0.04, P = 0.033), whereas in patients who were treated with adalimumab we observed an increase of the Foxp3/CD4 ratios after 1.5 and 16 weeks of treatment compared to baseline (t = 0: 0.25 AE 0.04; t = 1.5: 0.32 AE 0.06; t = 16: 0.49 AE 0.10, P = 0.15). Based on Foxp3/CD4 ratios, we can conclude that adalimumab treated skin differs from CBD treated skin with regard to the anti-inflammatory/ inflammatory balance. We suggest that, in contrast to CBD ointment, adalimumab favours local Treg function in the skin.