Neutrophilic granulocyte-derived B-cell activating factor supports B cells in skin lesions in hidradenitis suppurativa.

BACKGROUND: Hidradenitis suppurativa (HS) is a chronic inflammatory disease characterized by painful inflamed nodules, abscesses, and pus-draining tunnels appearing in axillary, inguinal, and perianal skin areas. HS lesions contain various types of immigrated immune cells. OBJECTIVE: This study aimed to characterize mediators that support lesional B/plasma cell persistence in HS. METHODS: Skin samples from several cohorts of HS patients and control cohorts were assessed by mRNA sequencing, quantitative PCR on reverse-transcribed RNA, flow cytometry, and immunohistofluorescence. Blood plasma and cultured skin biopsy samples, keratinocytes, dermal fibroblasts, neutrophilic granulocytes (neutrophils), monocytes, and B cells were analyzed. Complex systems biology approaches were used to evaluate bulk and single-cell RNA sequencing data. RESULTS: Proportions of B/plasma cells, neutrophils, CD8+ T cells, and M0 and M1 macrophages were elevated in HS lesions compared to skin of healthy and perilesional intertriginous areas. There was an association between B/plasma cells, neutrophils, and B-cell activating factor (BAFF, aka TNFSF13B). BAFF was abundant in HS lesions, particularly in nodules and abscesses. Among the cell types present in HS lesions, myeloid cells were the main BAFF producers. Mechanistically, granulocyte colony-stimulating factor in the presence of bacterial products was the major stimulus for neutrophils' BAFF secretion. Lesional upregulation of BAFF receptors was attributed to B cells (TNFRSF13C/BAFFR and TNFRSF13B/TACI) and plasma cells (TNFRSF17/BCMA). Characterization of the lesional BAFF pathway revealed molecules involved in migration/adhesion (eg, CXCR4, CD37, CD53, SELL), proliferation/survival (eg, BST2), activation (eg, KLF2, PRKCB), and reactive oxygen species production (eg, NCF1, CYBC1) of B/plasma cells. CONCLUSION: Neutrophil-derived BAFF supports B/plasma cell persistence and function in HS lesions.

Blood T Helper Memory Cells: A Tool for Studying Skin Inflammation in HS?

Hidradenitis suppurativa (HS) is an inflammatory skin disease characterized by painful lesions on intertriginous body areas such as the axillary, inguinal, and perianal sites. Given the limited treatment options for HS, expanding our knowledge of its pathogenetic mechanisms is a prerequisite for novel therapeutic developments. T cells are assumed to play a crucial role in HS pathogenesis. However, it is currently unknown whether blood T cells show specific molecular alterations in HS. To address this, we studied the molecular profile of CD4+ memory T (Thmem) cells purified from the blood of patients with HS and matched healthy participants. About 2.0% and 1.9% of protein-coding transcripts were found to be up- and down-regulated in blood HS Thmem cells, respectively. These differentially expressed transcripts (DETs) are known to be involved in nucleoside triphosphate/nucleotide metabolic processes, mitochondrion organization, and oxidative phosphorylation. The detected down-regulation of transcripts involved in oxidative phosphorylation suggest a metabolic shift of HS Thmem cells towards glycolysis. The inclusion of transcriptome data from skin from HS patients and healthy participants in the analyses revealed that in HS skin lesions, the expression pattern of transcripts identified as DETs in blood HS Thmem cells was very similar to the expression pattern of the totality of protein-coding transcripts. Furthermore, there was no significant association between the extent of the expressional changes in the DETs of blood HS Thmem cells and the extent of the expressional changes in these transcripts in HS skin lesions compared to healthy donor skin. Additionally, a gene ontology enrichment analysis did not demonstrate any association of the DETs of blood HS Thmem cells with skin disorders. Instead, there were associations with different neurological diseases, non-alcoholic fatty liver disease, and thermogenesis. The levels of most DETs linked to neurological diseases showed a positive correlation to each other, suggesting common regulatory mechanisms. In summary, the transcriptomic changes in blood Thmem cells observed in patients with manifest cutaneous HS lesions do not appear to be characteristic of the molecular changes in the skin. Instead, they could be useful for studying comorbidities and identifying corresponding blood biomarkers in these patients.

Interleukin-19 Levels Are Increased in Palmoplantar Pustulosis and Reduced following Apremilast Treatment.

Palmoplantar pustulosis (PPP) is a chronic inflammatory skin disease characterised by neutrophilic granulocyte (neutrophil)-filled pustules on the palms and soles. The pathogenesis of PPP is poorly understood. This study conducted an identification of the immune mediators associated with PPP and an exploration of apremilast treatment effects on them. We screened for immune mediators elevated in blood taken from 68 patients with PPP versus control participants and included the most promising parameters in the protocol of phase the 2, multicentre study of apremilast (PDE4 inhibitor) in 21 patients with moderate-to-severe PPP (APLANTUS; EudraCT 2016-005122-11) for respective analysis of blood and skin samples of study patients. We investigated stimulated neutrophils and three-dimensional reconstituted epidermis cultures. Interleukin (IL)-19 was found to be the most upregulated immune mediator in the blood of PPP patients. IL-19 serum levels were independent of patients' age, gender, and BMI but were associated with strongly upregulated cutaneous IL-19 expression and correlated with the number of palmoplantar pustules. In patients participating in the APLANTUS study, apremilast reduced pustules more effectively than erythema and scaling. Moreover, this treatment significantly reduced IL-19 blood and skin levels. The reduction in IL-19 blood levels at week 4 correlated with the reduction in pustule counts at week 20 (end of treatment). IL-19 was expressed by neutrophils activated in vitro and induced CXCL6, a neutrophil-attracting chemokine, in epidermis models. This work demonstrates elevated IL-19 levels in the blood and skin of PPP patients and suggests a relevant role of this cytokine in the appearance of pustules in this disorder. It also suggests the suitability of IL-19 blood levels as a predictive biomarker for the treatment response of PPP patients, which should be validated in further studies.

Phytotherapeuthics Affecting the IL-1/IL-17/G-CSF Axis: A Complementary Treatment Option for Hidradenitis Suppurativa?

Hidradenitis suppurativa (HS; also designated as acne inversa) is a chronic inflammatory disease characterized by painful skin lesions that occur in the axillary, inguinal, gluteal and perianal areas of the body. These lesions contain recurring deep-seated, inflamed nodules and pus-discharging abscesses and fistulas. Affecting about 1% of the population, this common disease has gained appropriate clinical attention in the last years. Associated with numerous comorbidities including metabolic syndrome, HS is considered a systemic disease that severely impairs the quality of life and shortens life expectancy. Therapeutic options for HS are limited, comprising long-term antibiotic treatment, the surgical removal of affected skin areas, and neutralization of TNF-α, the only approved systemic treatment. Novel treatment options are needed to close the therapeutic gap. HS pathogenesis is increasingly better understood. In fact, neutrophilic granulocytes (neutrophils) seem to be decisive for the development of the purulent destructive skin inflammation in HS. Recent findings suggest a key role of the immune mediators IL-1ß, IL-17A and G-CSF in the migration into and activation of neutrophils in the skin. Although phytomedical drugs display potent immunoregulatory properties and have been suggested as complementary therapy in several chronic disorders, their application in HS has not been considered so far. In this review, we describe the IL-1/IL-17/G-CSF axis and evaluate it as potential target for an integrated phytomedical treatment of HS.

MMP8 Is Increased in Lesions and Blood of Acne Inversa Patients: A Potential Link to Skin Destruction and Metabolic Alterations.

Acne inversa (AI; also designated as hidradenitis suppurativa) is a chronic inflammatory disease with still unknown pathogenesis that affects the intertriginous skin of perianal, inguinal, and axillary sites. It leads to painful nodules, abscesses, and fistulas with malodorous secretion and is frequently associated with metabolic alterations. Here, we demonstrate that one of the most highly upregulated molecules in AI lesions is matrix metalloproteinase 8 (MMP8), an enzyme specialized in the degradation of extracellular matrix components and the HDL component apolipoprotein A-I. Granulocytes, which were present in AI lesions, secreted high amounts of MMP8 especially after TNF-α stimulation. Furthermore, activated fibroblasts but not keratinocytes were found to express MMP8. The high lesional MMP8 levels were accompanied by elevated blood levels that positively correlated with TNF-α blood levels and disease severity assessed by Sartorius score, especially with the number of regions with inflammatory nodules/abscesses and fistulas. Additionally, we found a negative correlation between blood MMP8 and HDL-cholesterol levels, suggesting a contributory role of MMP8 in metabolic alterations in AI. In summary, we demonstrate elevated MMP8 levels in AI lesions, suggest their role in skin destruction and metabolic alterations, and recommend the use of MMP8 as blood biomarker for AI disease activity assessment.

Deficiency of IL-22 contributes to a chronic inflammatory disease: pathogenetic mechanisms in acne inversa.

Overexpression of the T cell cytokine IL-22 is linked to the development of some chronic diseases, but little is known about IL-22 deficiency in humans. As demonstrated in this study, acne inversa (AI; also designated as Hidradenitis suppurativa) lesions show a relative deficiency of IL-22 and IL-20, but not of IL-17A, IL-26, IFN-γ, IL-24, or IL-1ß. Moreover, AI lesions had reduced expression of membranous IL-22 and IL-20 receptors and increased expression of the natural IL-22 inhibitor, IL-22 binding protein. AI is a chronic inflammatory skin disease with prevalence up to 4% of the population and in which cutaneous bacterial persistence represents an important pathogenetic factor. Accordingly, we also found a relative deficiency of antimicrobial proteins (AMPs) in AI lesions and a positive correlation between lesional IL-22 and IL-20 versus AMP levels. IL-22, like its tissue cell downstream mediator IL-20, upregulated AMPs in reconstituted human epidermis and was critical for increased AMP levels under inflammatory conditions. The relative IL-22 deficiency in AI was not linked to lesional T cell numbers or Th22/Th1/Th17 subset markers and -inducing cytokines. However, IL-10 was highly expressed in AI lesions and correlated negatively with IL-22 expression. Moreover, IL-10 inhibited IL-22 but not IL-17 production in vitro. The IL-10 overexpression, in turn, was not associated with an elevated presence of regulatory T cells but with the enhanced presence of an IL-10-inducing cytokine. We conclude that IL-22 deficiency may contribute to the pathogenesis of certain chronic disorders as postulated in this paper for AI.

Molecular and functional changes in neutrophilic granulocytes induced by nicotine: a systematic review and critical evaluation.

Background: Over 1.1 billion people smoke worldwide. The alkaloid nicotine is a prominent and addictive component of tobacco. In addition to tumors and cardiovascular disorders, tobacco consumption is associated with a variety of chronic-inflammatory diseases. Although neutrophilic granulocytes (neutrophils) play a role in the pathogenesis of many of these diseases, the impact of nicotine on neutrophils has not been systematically reviewed so far. Objectives: The aim of this systematic review was to evaluate the direct influence of nicotine on human neutrophil functions, specifically on cell death/damage, apoptosis, chemotaxis, general motility, adhesion molecule expression, eicosanoid synthesis, cytokine/chemokine expression, formation of neutrophil extracellular traps (NETs), phagocytosis, generation of reactive oxygen species (ROS), net antimicrobial activity, and enzyme release. Material and methods: This review was conducted according to the PRISMA guidelines. A literature search was performed in the databases NCBI Pubmed® and Web of Science™ in February 2023. Inclusion criteria comprised English written research articles, showing in vitro studies on the direct impact of nicotine on specified human neutrophil functions. Results: Of the 532 originally identified articles, data from 34 articles were finally compiled after several evaluation steps. The considered studies highly varied in methodological aspects. While at high concentrations (>3 mmol/l) nicotine started to be cytotoxic to neutrophils, concentrations typically achieved in blood of smokers (in the nmol/l range) applied for long exposure times (24-72h) supported the survival of neutrophils. Smoking-relevant nicotine concentrations also increased the chemotaxis of neutrophils towards several chemoattractants, elevated their production of elastase, lipocalin-2, CXCL8, leukotriene B4 and prostaglandin E2, and reduced their integrin expression. Moreover, while nicotine impaired the neutrophil phagocytotic and anti-microbial activity, a range of studies demonstrated increased NET formation. However, conflicting effects were found on ROS generation, selectin expression and release of ß-glucuronidase and myeloperoxidase. Conclusion: Nicotine seems to support the presence in the tissue and the inflammatory and selected tissue-damaging activity of neutrophils and reduces their antimicrobial functions, suggesting a direct contribution of nicotine to the pathogenesis of chronic-inflammatory diseases via influencing the neutrophil biology.

Targeting Metabolic Syndrome in Hidradenitis Suppurativa by Phytochemicals as a Potential Complementary Therapeutic Strategy.

Hidradenitis suppurativa (HS) is a chronic inflammatory disease characterized by the appearance of painful inflamed nodules, abscesses, and pus-draining sinus tracts in the intertriginous skin of the groins, buttocks, and perianal and axillary regions. Despite its high prevalence of ~0.4-1%, therapeutic options for HS are still limited. Over the past 10 years, it has become clear that HS is a systemic disease, associated with various comorbidities, including metabolic syndrome (MetS) and its sequelae. Accordingly, the life expectancy of HS patients is significantly reduced. MetS, in particular, obesity, can support sustained inflammation and thereby exacerbate skin manifestations and the chronification of HS. However, MetS actually lacks necessary attention in HS therapy, underlining the high medical need for novel therapeutic options. This review directs attention towards the relevance of MetS in HS and evaluates the potential of phytomedical drug candidates to alleviate its components. It starts by describing key facts about HS, the specifics of metabolic alterations in HS patients, and mechanisms by which obesity may exacerbate HS skin alterations. Then, the results from the preclinical studies with phytochemicals on MetS parameters are evaluated and the outcomes of respective randomized controlled clinical trials in healthy people and patients without HS are presented.

Features Associated With Quality of Life Impairment in Hidradenitis Suppurativa Patients.

Background: Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease with an adverse impact on patients' quality of life (QoL). Objectives: To quantify QoL impairment in patients in Germany suffering from HS and to identify the parameters associated with QoL impairment. Methods: A non-interventional, cross-sectional, mono-centric study with 500 HS patients. QoL data (measured using the Dermatology Life Quality Index; DLQI) and demographic, anamnestic, clinical, and blood parameters were collected. All patients were examined by dermatologists that documented the skin alterations. QoL data from 462 HS patients were available and evaluated. Results: The mean (± standard deviation) DLQI score of HS patients was 13.18 ± 7.99. Approximately 40% and 20% of HS patients declared very large and extremely large QoL impairment, respectively. The degree of QoL disturbance correlated with the severity of skin alterations, blood leucocyte count and, in particular, with anogenital localization and the presence of nodules and fistulas. Furthermore, QoL impairment was associated with specific comorbidities, such as adiposity and back pain, but not with HS family history. QoL impairment was not influenced by whether or not the patients had undergone resection surgery or antibiotic treatment but was more severe in HS patients that had undergone abscess lancing compared to patients without such treatment in the past. Limitations: It was a mono-centric study and most data were obtained from self-administered patient questionnaires. The association of QoL with type of treatment was analyzed for abscess lancing, resection surgery, and antibiotic treatment. Further therapeutic modalities recommended in the guidelines were not investigated. Conclusion: A profound impairment in QoL was present in patients with HS, and this was higher than that observed in other studied dermatoses. The degree of impairment correlated with the extent of cutaneous and some extra-cutaneous alterations. Surgical and conventional medicamentous therapies of HS were not associated with long-lasting reduction of QoL impairment. Our data support the implementation of patient-reported outcome measures for the assessment of therapy responses.

The Th17 cytokine IL-22 induces IL-20 production in keratinocytes: a novel immunological cascade with potential relevance in psoriasis.

Psoriasis is a common chronic skin disease. Recent studies demonstrated that IL-20 and IL-22, cytokines produced by keratinocytes and T cells, respectively, both inhibit keratinocyte terminal differentiation and induce psoriasis-like epidermis alterations. Here, we investigated the relationship between these mediators. Although IL-20 was not able to regulate IL-22 production, IL-22 induced IL-20 mRNA and protein in human keratinocytes. However, IL-22 had only a minimal effect, if any, on IL-19 and IL-26. Cutaneous IL-20 was also elevated in mice following IL-22 application. Accordingly, some of IL-22's effects on differentiation-regulating genes were partially mediated by an endogenous, secreted protein and attenuated by anti-IL-20 Ab. Like IL-22, IL-17A and TNF-alpha induced IL-20 in keratinocytes, whereas IFN-gamma and IL-20 itself did not. Furthermore, IL-17A and TNF-alpha individually strengthened the IL-22-induced IL-20 production. In lesional skin of psoriasis patients, highly elevated IL-20 levels strongly correlated with IL-22, and to a lesser extent, with IL-17A and TNF-alpha. As previously shown for IL-22, IL-20 blood levels correlated with the disease severity, although with a lower significance. This study demonstrates that a T-cell mediator induces a tissue cell mediator with similar effects to its own and therefore suggests the existence of a novel type of pathogenetic cascade.

The herbal extract EPs® 7630 increases the antimicrobial airway defense through monocyte-dependent induction of IL-22 in T cells.

The phytotherapeutic compound EPs® 7630, an extract manufactured from Pelargonium sidoides roots, is frequently used for the treatment of airway infections. Nevertheless, the knowledge of the mode of action of EPs® 7630 is still sparse. Our study aimed at further elucidating the underlying pharmacological mechanisms by focusing on antimicrobial defense mechanisms of EPs® 7630. While investigating the influence of EPs® 7630 on lymphokine production by PBMCs, we found that EPs® 7630 is a novel inducer of IL-22 and IL-17. This cytokine-inducing effect was most pronounced for IL-22 and clearly dose-dependent starting from 1 µg/ml of the extract. Furthermore, EPs® 7630 pretreatment selectively enhanced the IL-22 and IL-17 production capacity of CD3/28-activated PBMCs while strongly limiting the IFN-γ production capacity of innate lymphoid cells. The relevance of EPs® 7630-induced IL-22 production was proven in vitro and in vivo, where IL-22 provoked a strong increase of the antimicrobial protein S100A9 in lung epithelial cells and pulmonary tissue, respectively. A detailed analysis of IL-22 induction modi revealed no direct influence of EPs® 7630 on the basal or anti-CD3/CD28 antibody-induced IL-22 production by CD4+ memory T cells. In fact, EPs® 7630-induced IL-22 production by CD4+ memory T cells was found to be essentially dependent on soluble mediators (IL-1/IL-23) as well as on direct cellular contact with monocytes. In summary, our study reveals a new immune-modulating function of EPs® 7630 that might confer IL-22 and IL-17-induced protection from bacterial airway infection. KEY MESSAGES: EPs® 7630 selectively strengthens IL-22 and IL-17 production of memory T cells. EPs® 7630 limits the IFN-y production capacity of innate lymphoid cells. EPs® 7630-caused IL-22 production by T cells is essentially dependent on monocytes. IL-22 increase antimicrobial proteins (AMPs) in airway epithelium. EPs® 7630 might protect against airway infection by induction of AMP-inducers.

Increased presence and differential molecular imprinting of transit amplifying cells in psoriasis.

Psoriasis is a very common chronic inflammatory skin disease characterized by epidermal thickening and scaling resulting from keratinocyte hyperproliferation and impaired differentiation. Pathomechanistic studies in psoriasis are often limited by using whole skin tissue biopsies, neglecting their stratification and cellular diversity. This study aimed at characterizing epidermal alterations in psoriasis at the level of keratinocyte populations. Epidermal cell populations were purified from skin biopsies of psoriasis patients and healthy donors using a novel cell type-specific approach. Molecular characterization of the transit-amplifying cells (TAC), the key players of epidermal renewal, was performed using immunocytofluorescence-technique and integrated multiscale-omics analyses. Already TAC from non-lesional psoriatic skin showed altered methylation and differential expression in 1.7% and 1.0% of all protein-coding genes, respectively. In psoriatic lesions, TAC were strongly expanded showing further increased differentially methylated (10-fold) and expressed (22-fold) genes numbers. Importantly, 17.2% of differentially expressed genes were associated with respective gene methylations. Compared with non-lesional TAC, pathway analyses revealed metabolic alterations as one feature predominantly changed in TAC derived from active psoriatic lesions. Overall, our study showed stage-specific molecular alterations, allows new insights into the pathogenesis, and implies the involvement of epigenetic mechanisms in lesion development in psoriasis. KEY MESSAGES: Transit amplifying cell (TAC) numbers are highly increased in psoriatic lesions Psoriatic TAC show profound molecular alterations & stage-specific identity TAC from unaffected areas already show first signs of molecular alterations Lesional TAC show a preference in metabolic-related alterations.

Maturing dendritic cells are an important source of IL-29 and IL-20 that may cooperatively increase the innate immunity of keratinocytes.

IL-19, IL-20, IL-22, IL-24, IL-26, IL-28, and IL-29 are new members of the IL-10 interferon family. Monocytes are well-known sources of IL-19, IL-20, and IL-24. We demonstrated here that monocytes also expressed IL-29, and monocyte differentiation into macrophages (Mphi) or dendritic cells (DCs) strongly changed their production capacity of these cytokines. Maturation of DCs with bacterial stimuli induced high expression of IL-28/IL-29 and IL-20. Simulated T cell interaction and inflammatory cytokines induced IL-29 and IL-20 in maturing DCs, respectively. Compared with monocytes, DCs expressed only minimal IL-19 levels and no IL-24. The differentiation of monocytes into Mphi reduced their IL-19 and terminated their IL-20, IL-24, and IL-29 production capacity. Like monocytes, neither Mphi nor DCs expressed IL-22 or IL-26. The importance of maturing DCs as a source of IL-28/IL-29 was supported by the much higher mRNA levels of these mediators in maturing DCs compared with those in CMV-infected fibroblasts, and the presence of IL-28 in lymph nodes but not in liver of lipopolysaccharide-injected mice. IL-19, IL-20, IL-22, IL-24, and IL-26 do not seem to affect Mphi or DCs as deduced from the lack of corresponding receptor chains. The significance of IL-20 and IL-28/IL-29 coexpression in maturing DCs may lie in the broadly amplified innate immunity in neighboring tissue cells like keratinocytes. In fact, IL-20 induced the expression of antimicrobial proteins, whereas IL-28/IL-29 enhanced the expression of toll-like receptors (TLRs) and the response to TLR ligands. However, the strongest response to TLR2 and TLR3 activation showed keratinocytes in the simultaneous presence of IL-20 and IL-29.

The IL-1 Pathway Is Hyperactive in Hidradenitis Suppurativa and Contributes to Skin Infiltration and Destruction.

Hidradenitis suppurativa (HS) (also designated acne inversa) is a chronic inflammatory disease characterized by painful purulent skin lesions and progressive destruction of skin architecture. Despite the high burden for the patients, pathogenetic pathways underlying HS alterations remain obscure. When we examined the HS cytokine pattern, IL-1ß turned out to be a highly prominent cytokine, overexpressed even compared with psoriatic lesions. Analyses of IL-1ß-induced transcriptome in various cell types showed overlapping profiles, with upregulations of molecules causing immune cell infiltration and extracellular matrix degradation, and of specific cytokines including IL-6, IL-32, and IL-36. Matching cellular IL-1 receptor levels, dermal fibroblasts showed both the strongest and broadest IL-1ß response, which was not clearly shared or strengthened by other cytokines. The IL-1ß signature was specifically present in HS lesions and could be reversed by application of IL-1 receptor antagonist. Search for blood parameters associated with IL-1ß pathway activity in HS identified serum amyloid A, which was synergistically induced by IL-1ß and IL-6 in hepatocytes. Consequently, strongly elevated blood serum amyloid A levels in HS correlated positively with the extent of inflammatory skin alterations. In summary, the IL-1ß pathway represents a pathogenetic cascade, whose activity may be therapeutically targeted and monitored by blood SAA levels.

Interleukin-29 induces epithelial production of CXCR3A ligands and T-cell infiltration.

UNLABELLED: Psoriasis is considered as a model for chronic immune-mediated disorders. Th17-cells are pivotal players in those diseases. Recently, we demonstrated that Th17-cells produce interleukin (IL)-29 and that IL-29 is highly present in psoriatic lesions. Whether IL-29, with its action on epithelial cells and melanocytes, contributes to psoriasis pathogenesis, was unknown so far. Analysis of IL-29-treated human keratinocytes revealed induction of the chemokines CXCL10, CXCL11, and, to a much lesser extent, CXCL9. Unlike these CXCR3A ligands, known to attract Th1-, CD8(+), NK-, and Th1/Th17 transient cells, no influence was found on chemokines attracting other immune cell populations or on molecules modulating the CXCR3A/CXCR3A ligand interaction. CXCR3A ligand expression was also induced by IL-29 in melanocytes and in epidermis models and explanted skin. Regarding other psoriasis-relevant cytokines, interferon-γ and, less potently, tumor necrosis factor-α and IL-1ß shared and strengthened IL-29's capacity. Murine IL-29 counterpart injected into mouse skin provoked local CXCL10 and CXCL11 expression, T-cell infiltration, and, in consequence, skin swelling. The elevated IL-29 expression in psoriatic lesions was associated with upregulation of CXCR3A ligands compared to non-lesional skin of these patients and to the skin of healthy donors and atopic dermatitis patients, which lack IL-29 production. Importantly, neutralization of IL-29 reduced CXCR3A ligand levels in explant cultures of psoriatic lesions. Finally, elevated blood CXCL11 levels were found in psoriasis that might be useful for monitoring lesional activity of the IL-29 axis. In summary, the Th17-cytokine IL-29 induces specific chemokines and, in consequence, provokes skin infiltration of potentially pathogenic T-cells. KEY MESSAGES: IL-29 selectively induces CXCR3A-binding chemokines (CXCL9, CXCL10, CXCL11) in skin cells. Murine IL-29 counterpart induces skin T-cell infiltration and inflammation in mice. CXCR3A ligands are IL-29-dependently increased in lesional skin of psoriasis patients. CXCR3A ligand levels in psoriatic skin correlate with epidermal T-cell numbers. Increased blood CXCL11 levels in psoriasis may be a biomarker for local IL-29 action.

The Pelargonium sidoides Extract EPs 7630 Drives the Innate Immune Defense by Activating Selected MAP Kinase Pathways in Human Monocytes.

Pelargonium sidoides is a medical herb and respective extracts are used very frequently for the treatment of respiratory tract infections. However, the effects of Pelargonium sidoides and a special extract prepared from its roots (EPs 7630) on human immune cells are not fully understood. Here we demonstrate that EPs 7630 induced a rapid and dose-dependent production of TNF-α, IL-6, and IL-10 by human blood immune cells. This EPs 7630-induced cytokine profile was more pro-inflammatory in comparison with the profile induced by viral or bacterial infection-mimicking agents. The search for EPs 7630 target cells revealed that T-cells did not respond to EPs 7630 stimulation by production of TNF-α, IL-6, or IL-10. Furthermore, pretreatment of T-cells with EPs 7630 did not modulate their TNF-α, IL-6, and IL-10 secretion during subsequent activation. In contrast to lymphocytes, monocytes showed clear intracellular TNF-α staining after EPs 7630 treatment. Accordingly, EPs 7630 predominantly provoked activation of MAP kinases and inhibition of p38 strongly reduced the monocyte TNF-α production. The pretreatment of blood immune cells with EPs 7630 lowered their secretion of TNF-α and IL-10 and caused an IL-6 dominant response during second stimulation with viral or bacterial infection-mimicking agents. In summary, we demonstrate that EPs 7630 activates human monocytes, induces MAP kinase-dependent pro-inflammatory cytokines in these cells, and specifically modulates their production capacity of mediators known to lead to an increase of acute phase protein production in the liver, neutrophil generation in the bone marrow, and the generation of adaptive Th17 and Th22 cells.

Deficient cutaneous antibacterial competence in cutaneous T-cell lymphomas: role of Th2-mediated biased Th17 function.

PURPOSE: Primary cutaneous T-cell lymphomas (CTCL) are neoplastic disorders of skin-homing T cells. Affected skin areas show morphologic similarities with alterations in other T-cell-mediated dermatoses. Furthermore, as in atopic dermatitis but in contrast with psoriasis, patients with CTCL are frequently afflicted by cutaneous bacterial infections that support the survival of lymphoma cells. Our aim was to investigate the mechanisms of elevated susceptibility to cutaneous infections in patients with CTCL. EXPERIMENTAL DESIGN: Skin samples from CTCL, psoriasis, and atopic dermatitis patients were used to illuminate the antibacterial competence status and the presence of its modulating cytokines. For substantiation of findings, 3-dimensional epidermis models, isolated and in vitro generated Th-subpopulations, were applied. Parameters were analyzed via qPCR and IHC. RESULTS: CTCL lesions compared with psoriatic lesions presented an impaired upregulation of antibacterial proteins (ABPs), with levels even below those in atopic dermatitis. This was associated with a relative deficiency of the ABP-inducing cytokine IL-17 and a strong presence of the ABP-downregulating cytokine IL-13. The simultaneous presence of the Th17-cell cytokine IL-26 indicated that IL-17 deficiency in CTCL lesions results from functional deviation of Th17 cells. Accordingly, IL-17 but not IL-26 production by Th17 cells in vitro was inhibited by IL-4Rα ligand. Levels of other ABP inducers were comparable between CTCL and psoriasis lesions. The same was true about IL-22/TNF-α targets, including the keratinocyte hyper-regeneration marker K16 and the matrix-degrading enzyme MMP1. CONCLUSION: Our results suggest that the cutaneous bacterial infections in CTCL are caused by impaired ABP induction as consequence of Th2-mediated biased Th17-cell function.

IL-19 is a component of the pathogenetic IL-23/IL-17 cascade in psoriasis.

Psoriasis is a common chronic inflammatory disease with characteristic skin alterations and functions as a model of immune-mediated disorders. Cytokines have a key role in psoriasis pathogenesis. Here, we demonstrated that out of 30 individually quantified cytokines, IL-19 showed the strongest differential expression between psoriatic lesions and healthy skin. Cutaneous IL-19 overproduction was reflected by elevated IL-19 blood levels that correlated with psoriasis severity. Accordingly, anti-psoriatic therapies substantially reduced both cutaneous and systemic IL-19 levels. IL-19 production was induced in keratinocytes by IL-17A and was further amplified by tumor necrosis factor-α and IL-22. Among skin cells, keratinocytes were found to be important targets of IL-19. IL-19 alone, however, regulated only a few keratinocyte functions. While increasing the production of S100A7/8/9 and, to a moderate extent, also IL-1ß, IL-20, chemokine C-X-C motif ligand 8, and matrix metalloproteinase 1, IL-19 had no clear influence on the differentiation, proliferation, or migration of these cells. Importantly, IL-19 amplified many IL-17A effects on keratinocytes, including the induction of ß-defensins, IL-19, IL-23p19, and T helper type 17-cell- and neutrophil-attracting chemokines. In summary, IL-19 as a component of the IL-23/IL-17 axis strengthens the IL-17A action and might be a biomarker for the activity of this axis in chronic inflammatory disorders.

Immunological changes in psoriasis patients under long-term treatment with fumaric acid esters: risk of Kaposi sarcoma occurrence?

BACKGROUND: Psoriasis is a chronic skin disorder. The most frequently used systemic anti-psoriatic therapy in Germany is fumaric acid esters (FAE). OBJECTIVES: We aimed to characterize immunological changes in psoriasis patients under FAE treatment. METHODS AND MATERIALS: Over 200 flow-cytometry analyses of blood from 27 psoriasis patients and histological, molecular, and serological analyses of samples from a patient who developed Kaposi sarcoma (KS) during FAE therapy were performed. RESULTS: The patients receiving FAE showed decreased CD8+ T cell counts, in particular during the first six months. The CD4+ T cell decline was less pronounced and delayed in time. In a patient with KS, we found a profound CD4 and CD8 lymphocytopenia, as well as a NK cell number reduction, although leukocyte and lymphocyte counts were within the recommended limits. The patient was HIV negative, but positive for HHV8. After cessation of FAE therapy, KS regressed. DISCUSSION: HHV8 infection and iatrogenic T cell reduction, prominently of CD8+ T cells, could have contributed to KS development in this patient. Therefore, we suggest a control of CD4+ and CD8+ T cell counts in addition to the commonly-used differential blood counts in patients with a higher HHV8 prevalence or at high risk of other latent viral infections.

IL-29 is produced by T(H)17 cells and mediates the cutaneous antiviral competence in psoriasis.

Psoriasis and atopic dermatitis (AD) are the most common chronic inflammatory skin diseases. Although both patient groups show strongly impaired skin barrier function, only AD patients frequently suffer from cutaneous viral infections. The mechanisms underlying the distinct susceptibilities to these pathogenetic and often life-threatening infections are unknown. We show that antiviral proteins (AVPs) such as MX1, BST2, ISG15, and OAS2 were strongly elevated in psoriatic compared to AD lesions and healthy skin. Of 30 individually quantified cytokines in psoriatic lesions, interleukin-29 (IL-29) was the only mediator whose expression correlated with the AVP levels. IL-29 was absent in AD lesions, and neutralization of IL-29 in psoriatic skin reduced AVP expression. Accordingly, IL-29 raised AVP levels in isolated keratinocytes, epidermis models, and human skin explants, but did not influence antibacterial protein production. AVP induction correlated with increased antiviral defense of IL-29-treated keratinocytes. Furthermore, IL-29 elevated the expression of signaling elements, resulting in increased sensitivity of keratinocytes toward its own action. We identified T helper 17 (T(H)17) cells as IL-29 producers and demonstrated their ability to increase the antiviral competence of keratinocytes in an IL-29-dependent manner. Transforming growth factor-ß and the activity of RORγt/RORα were most critical for the development of IL-29-producing T(H)17 cells. IL-29 secretion by these cells was dependent on NFAT and c-Jun N-terminal kinase and was inhibited by IL-4. These data suggest that T(H)17 cell-derived IL-29, which is absent in AD, mediates the robust antiviral state on psoriatic skin, and demonstrate a new function of T(H)17 cells.