Increased expression of IL‐33 in rosacea skin and UVB‐irradiated and LL‐37‐treated HaCaT cells

Rosacea is one of the most common dermatoses of adults. Although the detailed pathophysiology remains unknown, it is thought that rosacea is caused by a consistently aberrant, innate immune response, and that LL‐37 plays an important role. However, involvement of the inflammatory cytokine IL‐33 has not yet been studied. We explored the role played by IL‐33 in the pathophysiology of rosacea. First, we immunohistochemically evaluated the expression of IL‐33 and its receptor (ST2) in rosacea skin. Second, we exposed HaCaT cells to ultraviolet B (UVB) irradiation in the presence or absence of LL‐37 and measured the expression of proinflammatory cytokines including IL‐33. We also analysed VEGF (vascular endothelial growth factor) mRNA expression and protein release after costimulation of HaCaT cells by LL‐37 and IL‐33. Immunohistochemically, IL‐33 expression was enhanced in the skin of rosacea patients, especially with erythematotelangiectatic subtype. In vitro, UVB and LL‐37 synergistically increased mRNAs expression of proinflammatory cytokines, especially IL‐33 and IL‐1β. IL‐33 protein release was also synergistically increased by LL‐37 and UVB treatment. LL‐37 and IL‐33 stimulated VEGF mRNA expression and VEGF release from HaCaT cells. Our findings suggest that rosacea skin with abundant LL‐37 may robustly produce and release IL‐33 when exposed to UV radiation. IL‐33 may participate in the angiogenesis and vasodilation of rosacea skin by enhancing VEGF release.     

Immunohistological pointers to a possible role for excessive cathelicidin (LL-37) expression by apocrine sweat glands in the pathogenesis of hidradenitis suppurativa/acne inversa

Summary Background The cause of follicular occlusion, a key early event in the pathogenesis of hidradenitis suppurativa (HS), also known as acne inversa, remains unknown. Objectives To identify changes, if any, in the antimicrobial peptide (AMP) and cytokine expression profile of HS affected human skin. Methods Quantitative immunohistomorphometry was used to compare the in situ protein expression of selected AMPs and cytokines in lesional HS skin from 18 patients with that in healthy skin (n = 12). The lesional skin from patients with HS was histologically subclassified based on the predominance of inflammation vs. scarring. Results Compared with healthy controls, significantly increased immunoreactivity for cathelicidin (LL‐37) was noted in the apocrine sweat gland and distal outer root sheath (ORS) of the hair follicle (HF) epithelium in lesional HS skin. Immunoreactivity for LL‐37, psoriasin, human β‐defensin 3 (hBD3), α‐melanocyte stimulating hormone (α‐MSH), macrophage migration inhibitory factor (MIF), tumour necrosis factor (TNF)‐α and interleukin (IL)‐8 was significantly increased in HS epidermis. LL‐37 and TNF‐α immunoreactivity was also increased in the dermis of lesional HS skin. In contrast, lysozyme expression was decreased in the epidermis of lesional HS skin, while that of TNF‐α and IL‐8 was decreased in the proximal ORS of HFs in HS lesions. These differences were most pronounced in HS with predominant inflammation. Conclusions Our observations raise the question as to whether excessive secretion of AMPs by the skin, in particular by the apocrine sweat glands, distal HF epithelium, and epidermis, may attract inflammation and thus facilitate or promote HS development.     

Mild electrical stimulation with heat shock reduces inflammatory symptoms in the imiquimod‐induced psoriasis mouse model

Psoriasis is a chronic skin disease caused by immune disorder. The chronic skin inflammation involves inflammatory molecules that are released from T lymphocytes and keratinocytes. Therefore, developing an anti‐inflammatory therapy that is suitable for long‐term treatment is needed. Electrical stimulation induces biological responses by modulating intracellular signaling pathways. Our previous studies showed that the optimized combination treatment of mild electrical stimulation (MES, 0.1‐millisecond; ms, 55‐pulses per second; pps) and heat shock (HS, 42°C) modulates inflammatory symptoms of metabolic disorders and chronic kidney disease in mice models and clinical trials. Here, we investigated the effect of MES+HS treatment on imiquimod‐induced psoriasis mouse model. Topical application of imiquimod cream (15 mg) to mice ear induced keratinocyte hyperproliferation and psoriasis‐like inflammation. In MES+HS‐treated mice, imiquimod‐induced skin hyperplasia was significantly decreased. MES+HS treatment reduced the protein expression of IL‐17A and the infiltration of CD3‐positive cells in lesioned skin. In addition, MES+HS‐treated mice had decreased mRNA expression level of antimicrobial molecules (S100A8 and Reg3γ) which aggravate psoriasis. In IL‐17A‐stimulated HaCaT cells, MES+HS treatment significantly lowered the mRNA expression of aggravation markers (S100A8, S100A9 and β‐defensin2). Taken together, our study suggested that MES+HS treatment improves the pathology of psoriasis via decreasing the expression of inflammatory molecules.     

Th17 cytokines interleukin (IL)-17 and IL-22 modulate distinct inflammatory and keratinocyte-response pathways

Background Psoriasis vulgaris is an inflammatory skin disease mediated by Th1 and Th17 cytokines, yet the relative contribution of interferon (IFN)‐γ, interleukin (IL)‐17 and IL‐22 on disease pathogenesis is still unknown. Objectives In this study, we sought to identify the cytokines produced by skin‐resident T cells in normal skin, localize the receptors for these cytokines, and examine how these cytokines alter gene expression profiles of the cells bearing cognate receptors. Methods We used intracellular cytokine staining and flow cytometry to evaluate T cell cytokine production, and immunohistochemistry and double‐label immunofluorescence to localize cytokine receptors in skin. Gene array analysis of cytokine‐treated keratinocytes was performed using moderated paired t‐test controlling for false discovery rate using the Benjamini–Hochberg procedure. Results We demonstrate that T‐helper cells producing IL‐17, IL‐22 and/or IFN‐γ, as well as the cells bearing cognate cytokine receptors, are present in normal human skin. Keratinocytes stimulated with IL‐17 expressed chemokines that were different from those induced by IFN‐γ, probably contributing to the influx of neutrophils, dendritic cells and memory T cells into the psoriatic lesion. In contrast, IL‐22 downregulated genes associated with keratinocyte differentiation and caused epidermal alterations in an organotypic skin model. Conclusions Our results suggest that the Th17 cytokines IL‐17 and IL‐22 mediate distinct downstream pathways that contribute to the psoriatic phenotype: IL‐17 is more proinflammatory, while IL‐22 retards keratinocyte differentiation.     

Serum Th1/Th2 and macrophage lineage cytokines in leprosy; correlation with circulating CD4+ CD25highFoxP3+ T‐regs cells

Not only macrophages, T‐helper (Th)1 and Th2, but also CD4⁺ CD25^highFoxP3⁺ regulatory T cells (T‐regs) are involved in immune response to Mycobacterium leprae. We aimed to evaluate serum interleukin (IL)‐1β and IL‐12p70 (macrophage cytokines), interferon‐γ (IFN‐γ) (Th1 cytokine), IL‐4 (Th2 cytokine) and circulating CD4⁺ CD25^highFoxP3⁺ T‐regs, in untreated leprosy patients. Forty three patients and 40 controls were assessed for the mentioned cytokines using ELISA. Patients were assessed for circulating T‐regs using flow cytometry. Patients were subgrouped into tuberculoid (TT), pure neural leprosy (PNL), borderline cases, lepromatous (LL), type 1 reactional leprosy (RL1) and erythema nodosum leprosum (ENL). Serum IL‐12p70, IFN‐γ and IL‐4 were significantly higher in patients versus controls (P < 0.05). Serum IL‐4 was highest in LL and lowest in RL1 (P = 0.003). Serum IL‐1β levels was significantly higher in multibacillary versus paucibacillary patients (P = 0.006). Significantly higher T‐regs levels was detected in TT, RL1 and PNL, while the lowest levels in ENL(P < 0.001), with significant differences versus controls (P < 0.05). FoxP3 expression% was significantly lower in PNL than other patients and controls (P < 0.05). T‐regs/T‐effs was lowest in ENL(P < 0.05). IFN‐γ correlated positively with T‐regs but negatively with IL‐1β (P = 0.041&0.046 respectively), which correlated positively with T‐effs%( P = 0.05). IL‐4 correlated positively with T‐regs FoxP3 expression% (P = 0.009). We concluded that: Circulating T‐regs were increased in TT, RL1 and PNL patients, known of relatively high cell‐mediated immunity. This finding was supported by low FoxP3 expression (in PNL) and correlation between T‐regs count and IFN‐γ level. Overproduction of IL‐4 in LL may infer liability to develop ENL, with disease progression and immune hyperactivation, marked by deficient T‐regs and increased T‐regs FoxP3 expression%. IL‐1β probably has a pro‐inflammatory role in multibacillary patients as correlated with T‐effs%.     

Lipocalin‐2 exacerbates psoriasiform skin inflammation by augmenting T‐helper 17 response

Lipocalin‐2 (LCN2) is an antimicrobial protein and adipokine associated with insulin resistance, obesity and atherosclerotic disease. Psoriasis is a T‐helper (Th)1/Th17‐mediated, chronic inflammatory dermatosis related to metabolic syndromes and serum LCN2 levels are elevated in psoriatic patients. We examined the in vivo effects of LCN2 on topical imiquimod (IMQ)‐induced psoriasiform skin in BALB/c mice and in vitro on human keratinocytes (KC). Clinically, i.p. injected LCN2 exacerbated erythema and scaling in IMQ‐treated murine skin compared with phosphate‐buffered saline injection alone, and it augmented interleukin (IL)‐17A, IL‐17F, IL‐22, IL‐23p19, IL‐12p40, CCL20, tumor necrosis factor‐α, chemokine (C‐X‐C motif) ligand (CXCL)1, CXCL2, DEFB4, DEFB14, LCN2 and S100A7 mRNA levels of IMQ‐treated murine skin while it did not increase the mRNA levels of interferon‐γ, IL‐12p35 or CXCL10. LCN2 in synergy with IL‐17 increased mRNA levels of CCL20, LCN2 and DEFB4A but not of CXCL10 in human KC in vitro. These results suggest that LCN2 enhances the expression of Th17 cytokines/chemokines and antimicrobial peptides in murine IMQ‐treated psoriatic skin and KC. LCN2 may potentiate the development of psoriasis via the enhancement of Th17‐ and antimicrobial peptide‐mediated inflammation.     

Adalimumab (antitumour necrosis factor-α) treatment of hidradenitis suppurativa ameliorates skin inflammation: an in situ and ex vivo study

Background Hidradenitis suppurativa (HS) is a difficult‐to‐manage disease. Randomized controlled trials with antitumour necrosis factor (TNF)‐α biologics have been conducted and in most studies disease activity was reduced. However, the mechanism of action in HS skin is so far unknown. Objectives To assess whether anti‐TNF‐α treatment affects in situ cytokine production and frequency of inflammatory cell populations in HS lesional skin. Methods Nine patients with HS, participating in a larger placebo‐controlled, double‐blind phase IIb clinical trial on the efficacy and safety of adalimumab in patients with moderate to severe HS (M10‐467), were randomized and treated for 16 weeks. In a mechanism‐of‐action substudy, biopsies were obtained at fixed time points pre‐ and post‐treatment. One part of the biopsy was cultured for 24 h for cytokine release in the culture medium, while another part was used for in situ analysis. Results Secretion of cytokines, including interleukin (IL)‐1β, CXCL9 [monokine induced by interferon‐γ (MIG)], IL‐10, IL‐11, B‐lymphocyte chemoattractant (BLC) and IL‐17A, was significantly elevated in HS. Adalimumab treatment was associated with decreased production of cytokines in HS skin, especially IL‐1β, CXCL9 (MIG) and BLC. Treatment significantly reduced the number of CD11c+, CD14+ and CD68+ cells in HS lesional skin. The numbers of CD3+ and CD4+ T cells, and CD20+ and CD138+ B cells were also reduced by adalimumab treatment. Conclusions Adalimumab treatment inhibits important cytokines and inflammatory cell numbers in lesional HS skin, especially levels of IL‐1β and numbers of inflammatory CD11c+ dendritic cells.     

Interleukin‐36 in hidradenitis suppurativa: evidence for a distinctive proinflammatory role and a key factor in the development of an inflammatory loop

Scientists from Germany investigated whether a cytokine called interleukin‐36 (IL‐36) might be important in hidradenitis suppurativa (HS), a chronic, painful, disfiguring and offensive‐smelling pustular skin disease that affects the armpits, groins, buttocks and breasts. A cytokine is a molecule produced by one cell that switches on other cells in some way ‐ for example, activating immune system cells to home in on sites of damage, including damage from infection. This is a complex chain reaction or loop. If cytokines are produced when they should not be produced, instead of the immune system repairing damage or combating infection as it should, inappropriate inflammation such as that seen in HS can result. This study of skin samples from 15 patients with moderately severe or severe HS found elevated levels of all three subtypes of IL‐36, mainly in the cells called keratinocytes: subtype IL‐36α particularly in affected skin, IL‐36β in skin around affected skin, and IL‐36γ in both. It also demonstrated an imbalance of cytokines IL‐37 and ‐38, which oppose the action of IL‐36. These findings suggest that the immune system plays an important role in the development of HS. They fit the theory that high IL‐36 levels kick off a chain reaction (which includes other interleukins and a particular type of white blood cell called a T‐helper cell) that results in inflammation and sufficient white blood cells to produce the pus that is a major feature of the condition.     

Human antimicrobial peptides LL-37 and human β-defensin-2 reduce viral replication in keratinocytes infected with varicella zoster virus

Background. There is mounting evidence that antimicrobial peptides have an important role in cutaneous defence, but the expression of these antimicrobial peptides in atopic eczema (AE) is still unclear. There are several families of antimicrobial peptides, including cathelicidins and human β‐defensins. Patients with AE are more susceptible to severe cutaneous viral infections, including varicella zoster virus (VZV). Aim. To characterize the functional activity of the antimicrobial peptides LL‐37 (human cathelicidin) and human β‐defensin (hBD)‐2 keratinocytes were infected with VZV, in a skin‐infection model. Methods. Flow‐cytometry analysis was used to investigate LL‐37 expression in normal human keratinocytes, and quantitative PCR was used to determine viral loads in infected HaCaT keratinocytes and B cells, with and without exogenous LL‐37 and hBD‐2. Results. LL‐37 expression was present in keratinocytes, and both exogenous LL‐37 and hBD‐2 significantly reduced VZV load in infected keratinocytes and B cells. Specific antibodies blocked the antiviral action exhibited by these antimicrobial peptides. Pre‐incubation of VZV with LL‐37, but not hBD‐2, further reduced VZV load. Conclusions. Both LL‐37 and hBD‐2 have an antiviral effect on VZV replication in the keratinocyte HaCaT cell line and in B cells, but their mechanism of action is different. Evidence of the relationship between antimicrobial peptide expression and higher susceptibility to infections in AE skin is still emerging. Developing novel antiviral therapies based on antimicrobial peptides may provide improved treatment options for patients with AE.     

Elevated levels of tumour necrosis factor (TNF)-α, interleukin (IL)-1β and IL-10 in hidradenitis suppurativa skin: a rationale for targeting TNF-α and IL-1β

Background The pathogenesis of hidradenitis suppurativa (HS) is largely unknown and the disease is difficult to treat. Patients are in high need of an effective treatment. Although it is not known whether the levels of tumour necrosis factor (TNF)‐α are aberrant in HS skin, anti‐TNF‐α biologics are used, with variable clinical efficacy. Objectives To determine the cytokine profile in lesional and perilesional HS skin. Methods We cultured 20 lesional and 10 normal‐appearing perilesional HS skin samples, seven psoriasis and six healthy control skin samples in a transwell culture system. Two distinct cytokine bead arrays were used to measure the spectrum of inflammatory cytokines in the culture supernatant. Results from HS skin samples were compared with those of healthy and psoriasis skin. Results The proinflammatory cytokines interleukin (IL)‐1β and TNF‐α as well as the anti‐inflammatory cytokine IL‐10 were significantly elevated in HS skin. Elevated levels of these cytokines were also found in perilesional HS skin. Fold increases relative to control skin of IL‐1β, TNF‐α and IL‐10 in HS were 31, 5 and 34, compared with psoriasis: 4, 1 and 2, respectively. Levels of all three cytokines showed a trend towards a positive correlation with disease severity. IL‐2, IL‐4, IL‐5 and interferon‐γ were hardly detectable in HS or healthy control skin. Conclusions This study shows for the first time that IL‐1β, TNF‐α and IL‐10 levels are elevated in HS skin. These data provide a rationale for therapies with biologics targeting cytokines such as TNF‐α and IL‐1.     

Autoantigens ADAMTSL5 and LL37 are significantly upregulated in active Psoriasis and localized with keratinocytes,dendritic cells and other leukocytes

Psoriasis is a common immune‐mediated disease that affects 2%‐4% of individuals in North America and Europe. In the past decade, advances in research have led to an improved understanding of immune pathways involved in the pathogenesis of psoriasis and has spurred the development of targeted therapeutics. Recently, three psoriasis autoantigens have been described: cathelicidin (LL37), a disintegrin and metalloprotease domain containing thrombospondin type 1 motif‐like 5 (ADAMTSL5), and lipid antigens generated by phospholipase A2 (PLA2) group IVD (PLA2G4D). It is important to establish the expression, regulation and therapeutic modulation of these psoriasis autoantigens. In this study, we performed immunohistochemistry and two‐colour immunofluorescence on non‐lesional and lesional psoriasis skin to characterize ADAMTSL5 and LL37, and their co‐expression with T cells, dendritic cells, neutrophils and macrophages, which are the main immune cells that drive this disease. Our results showed that ADAMTSL5 and LL37 are significantly (P<.05) increased in lesional skin and are co‐expressed by many dendritic cells, macrophages and some T cells in the dermis. Gene expression analysis showed significant (P<.05) upregulation of LL37 in lesional skin and significant downregulation following treatment with etanercept. ADAMTSL5 and LL37 are also significantly decreased by IL‐17 or TNF‐α blockade, suggesting feed‐forward induction of psoriasis autoantigens by disease‐related cytokines.     

Expression of Antimicrobial Peptides Such as LL‐37 and hBD‐2 in Nonlesional Skin of Atopic Individuals

Abstract: Recurrent skin infection is one of the major complications of atopic dermatitis and can be partly explained by decreased expression of antimicrobial peptides such as human β‐defensin‐2 and cathelicidin (LL‐37). In the human epidermis, human β‐defensin‐2 is packed in the lamellar body and LL‐37 is co‐localized with intercellular lipid lamellae of the stratum corneum; together, these antimicrobial peptides constitute the primary defense system. IL‐1α, a potent inducer of LL‐37 and human β‐defensin‐2, is also secreted from the disrupted epidermis for barrier homeostasis. In this study, we investigated whether expression of human β‐defensin‐2 and LL‐37 is constitutively decreased in the skin of atopic individuals. Nonlesional foreskins from atopic (n = 7) and nonatopic (n = 7) individuals were analyzed. The expression of LL‐37, human β‐defensin‐2 and IL‐1α was analyzed using immunohistochemical staining, Western blot, and real‐time polymerase chain reaction. Lamellar body density and secretion were evaluated by electron microscope. Quantitative analysis showed that the expression of each parameter was not significantly different between groups. Thus, basal expression of LL‐37 and human β‐defensin‐2 was not changed in atopic individuals. These results indicate that the expression of antimicrobial peptides at baseline was not different between nonlesional skin of atopic individuals and normal skin of nonatopic individuals.     

Interleukin‐21 receptor signalling is not critically required for imiquimod‐induced psoriasiform dermatitis in mice

Psoriasis is largely mediated by interleukin (IL)‐23/T helper (Th) 17 axis, and IL‐21 is a pleiotropic cytokine expressed by Th17 cells. Despite previously reported possible pathogenic roles of IL‐21 in human psoriasis, we found that IL‐21 receptor (IL‐21R) signalling was not crucial for imiquimod‐induced psoriatic inflammation, using IL‐21R^?/? mice. The severity of imiquimod‐induced psoriatic manifestation and pro‐inflammatory Th17 cytokine levels, IL‐17A‐producing γδ T cells and CD4+ T cells, and in vitro IL‐17A production by γδ T cells after IL‐23 stimulation was comparable between wild‐type and IL‐21R^?/? mice. Collectively, IL‐21R signalling was not critically involved in IMQ‐induced psoriatic inflammation despite an increased IL‐21 expression in the IMQ‐treated mouse skin. Our data may represent the significant differences between human psoriasis and murine psoriasis model, and further studies using other models will be required to elucidate the role of IL‐21 in psoriasis pathogenesis.     

Recombinant erythroid differentiation regulator 1 inhibits both inflammation and angiogenesis in a mouse model of rosacea

The erythroid differentiation regulator 1 (Erdr1), which is a novel and highly conserved factor, was recently reported to be negatively regulated by IL‐18 and to play a crucial role as an antimetastatic factor. IL‐18 is a proinflammatory cytokine that functions as an angiogenic mediator in inflammation. Rosacea is a chronic inflammatory skin disorder that is characterized by abnormal inflammation and vascular hyperactivity of the facial skin. To determine whether Erdr1 contributes to the regulation of the chronic inflammatory process in the development of rosacea, an immunohistochemical analysis was performed in healthy donors and patients with rosacea. In this study, we showed that Erdr1 was downregulated, whereas IL‐18 was upregulated, in patients with rosacea, which led us to question the role of Erdr1 in this disorder. Moreover, a rosacea‐like BALB/c mouse model was used to determine the role of Erdr1 in rosacea in vivo. LL‐37 injection induced typical rosacea features, including erythema, telangiectasia and inflammation. Treatment with recombinant Erdr1 (rErdr1) resulted in a significant reduction of erythema, inflammatory cell infiltration (including CD4⁺ and CD8⁺ T cells), and microvessel density with vascular endothelial growth factor (VEGF). Taken together, our findings suggest that rErdr1 may be involved in attenuating the inflammation and angiogenesis associated with the pathogenesis of rosacea. Thus, these results provide new insight into the mechanism involved in this condition and indicate that rErdr1 could be a potential target for therapeutic intervention of rosacea.     

Immunoglobulin G4‐related disease presenting with prurigo: Circulating T‐helper 2 cells may be involved in the pathogenesis

We report a case of immunoglobulin G4‐related disease (IgG4‐RD) which presented with prurigo on the trunk and extremities. A 66‐year‐old man had a 2‐month history of itchy erythematous papules on his trunk and extremities. Bilateral eyelid swelling and enlargement of the submandibular and parotid glands were also observed. Computed tomography revealed pleural thickening and diffuse pancreatic enlargement. Serum levels of IgG4 were markedly increased. A biopsy specimen obtained from an erythematous papule showed a perivascular inflammatory infiltrate of lymphocytes with eosinophils in the dermis, whereas a parotid gland biopsy revealed an infiltrate of abundant IgG4‐positive plasma cells. Treatment with prednisolone resulted in improvement of the skin and other lesions along with a decrease in IgG4 serum levels. A flow cytometric assay revealed that percentages of interleukin (IL)‐4‐ and IL‐13‐producing CD4⁺ T cells were markedly higher in the circulation of the IgG4‐RD patient than in that of healthy subjects. Moreover, those populations dramatically decreased after treatment. Thus, prurigo may be a skin manifestation of IgG4‐RD and T‐helper 2 cells may contribute to the pathogenesis.     

Dermatologic toxicity from novel therapy using antimicrobial peptide LL‐37 in melanoma: A detailed examination of the clinicopathologic features

LL‐37 is a naturally occurring 37‐amino‐acid peptide that is part of the innate immune system in human skin. Preclinical studies have showed that intra‐tumoral injections of LL‐37 stimulate the innate immune system by activation of plasmacytoid dendritic cells, which mediate tumor destruction. LL‐37 intra‐tumoral injections have been utilized in a phase 1 clinical trial for melanoma patients with cutaneous metastases. We report dermatologic toxicity in a 63‐year‐old woman with stage IIIC melanoma of the right calf and inguinal lymph nodes. She was previously treated with nivolumab and combination chemotherapy (cisplatin, vinblastine and dacarbazine) and subsequently treated with LL‐37 injections upon progression of both prior regimens. She received a total of 8 weekly LL‐37 injections, with interval clinical shrinkage of injected lesions. However, approximately 45 days after initiation of this therapy, she presented with multiple verrucous papules and a vesiculo‐bullous lesion on the trunk and extremities. Clinically, most of these lesions were thought to be either squamous cell carcinoma or inflamed seborrheic keratosis. Histologically, 11 of the total 12 skin biopsies showed similar histopathologic features, with a prominent lichenoid inflammatory infiltrate admixed with eosinophils and an overlying atypical squamous epithelial proliferation with verrucous and keratoacanthoma‐like features and varying degrees of keratinocytic atypia. Interestingly, a majority of the lesions did not show spongiosis (11/12). All lesions resolved within 2 months of cessation of LL‐37 injection therapy. This case highlights adverse dermatological manifestations of LL‐37 therapy, similar to the consequences of other novel therapies.     

IL‐1 signalling determines the fate of skin grafts expressing non‐self protein in keratinocytes

Please cite this paper as: IL‐1 signalling determines the fate of skin grafts expressing non‐self protein in keratinocytes. Experimental Dermatology 2010; 19 : 723–729. Abstract: Although IL‐1 is a known inflammatory cytokine during pathogen infection, the role of IL‐1 in skin graft rejection, particularly where foreign antigen is expressed exclusively in keratinocytes, is less understood. Here, we use a syngeneic skin graft system, where antigens are expressed in epithelial cells via either a keratin 14 or keratin 5 promoter, to explore the role of IL‐1 in graft rejection and induction of epithelial antigen‐specific effector CD8⁺ T‐cell function. Keratin 5 ovalbumin (K5mOVA) transgenic skin grafts destined for rejection demonstrated increased expression of IL‐1β and its receptors compared to K14 HPV16 E7 transgenic grafts that do not reject spontaneously. Rejection of OVA grafts lacking the IL‐1 receptor (IL‐1R1) was delayed and associated with decreased numbers of antigen‐specific CD8 T cells. In contrast, K14E7 grafts survived on immunocompetent, syngeneic recipients with decreased graft levels of IL‐1β and IL‐1R1 and 2. However, in the absence of the IL‐1 receptor antagonist, IL‐1Ra, skin grafts were spontaneously rejected and an E7‐specific CD8 T‐cell response was primed. Thus, expression of the HPV16E7 oncoprotein in epithelial cells prevents IL‐1β‐associated skin graft rejection and induction of antigen‐specific CD8 T‐cell responses. Enhancing IL‐1β signalling, via blocking of the IL‐1 receptor antagonist, may represent an alternative strategy for treatment of HPV16E7‐associated cancers.     

Interleukin‐1 from epithelial cells fosters T cell‐dependent skin inflammation

Background Chronic inflammatory skin diseases such as atopic dermatitis and psoriasis are characterized by the infiltration of lymphocytes into the epidermal compartment. Several studies point to an active role of skin epithelial cells in the pathophysiology of such diseases. Objectives In this study we addressed the regulatory function of primary human keratinocytes in the interaction with autologous T cells and monocytes. Methods We used a human coculture model with keratinocytes grown from epidermal stem cells of the outer root sheath of human hair follicles and autologous T cells. Results In our coculture system we observed a high production of interferon (IFN)‐γ, but not Th2 cytokines, in the presence of superantigen or antigen‐pulsed autologous monocytes. Critical parameters for this effect were: (i) T‐cell receptor activation, (ii) an intercellular adhesion molecule‐1/lymphocyte function‐associated antigen (LFA)‐1‐dependent interaction between keratinocytes and T cells, and (iii) secretion of interleukin (IL)‐1β. Remarkably, in the presence of activated T cells, epithelial cells seemed to be a more significant source of IL‐1β than monocytes. Application of the LFA‐1 blocker efalizumab or IL‐1 receptor antagonist anakinra enabled us to suppress completely the production of IFN‐γ by T cells in the coculture. Conclusions IL‐1 secretion and the physical contact between keratinocytes and activated, infiltrating T cells may be central for the development of chronic inflammatory skin conditions.     

Matrix remodelling and MMP expression/activation are associated with hidradenitis suppurativa skin inflammation

Hidradenitis suppurativa/acne inversa (HS) is a chronic, inflammatory, recurrent, debilitating skin disease of the hair follicle, associated with considerable tissue remodelling. Although abnormal cytokine expression was detected both in perilesional and in uninvolved skin, up to now there is no model allowing a better understanding of the implicit inflammatory mechanisms in HS. The aim of this study was to investigate the inflammatory response in HS skin by mean of an ex vivo model culture. To that purpose, nine skin biopsy specimens from patients suffering from HS and controls were cultured up to 4 days. Microscopy imaging investigations showed variations of collagen I and III organization, and an increase in elastin fibres fragmentation in HS skin after 4 days of culture. The HS matrix structure remodelling was associated with high level of MMP‐2 and MMP‐9 in HS lesional skin. After 4 days of culture, the MMP expression in HS perilesional skin reached the level observed in HS lesional skin. Concomitantly, an increase in IL‐1β concentration was observed in all skin samples after 4 days of culture, although IL‐1β concentrations remained significantly higher in HS lesional skin as compared with control skin. Meanwhile, neither IL‐17 concentrations nor the inflammasome components NLRP3 and caspase‐1 varied. Thus, our HS skin model culture showed that MMP‐induced matrix alteration could participate in HS inflammation by releasing biological active peptides and inflammatory factors from the extracellular matrix (ECM), and open new opportunities to investigate the regulation of the inflammatory mechanism associated with HS.