Cutaneous Immunity Research Articles

Acquired resistance against skin penetration by Strongylodies rattiis dependent on IL-33 expressing APCs

Abstract Interleukin 33 (IL-33) is an alarmin cytokine released from damaged epithelia that is essential for protection against gastrointestinal (GI) helminth (worm) infection, but whether IL-33 serves any role in cutaneous immunity against parasites remains unclear. While epithelial cells are considered the predominant source of IL-33, our recent work demonstrates that CD11c+ myeloid antigen presenting cells can express IL-33 to shape Type 2 immunity. We developed a percutaneous infection model using Strongylodies ratti, a rodent-specific GI helminth, to better understand mechanisms of host protection and the potential role for IL-33. Data show that C57BL/6 mice develop resistance to percutaneous infection upon secondary challenge, but IL-33 deficient mice lack this capacity. Surprisingly, mice with a selective IL-33 deficiency only in myeloid APC (CD11c Cre) also failed to develop secondary resistance to S. ratti, suggesting myeloid-derived IL-33 is essential for cutaneous immunity. Mechanistically, we find that loss of myeloid IL-33 impairs recruitment of gd T cells that express the IL-33 receptor ST2 and gene deficient mice that lack all gd T cells show defective protective immunity against S. ratti. Moreover, we propose that IL-33 drives a noncanonical Type 2 immunity, because mice lacking the Type 2 transcription factor STAT6 (Signal transducer and activator of transcription 6), have no defects in primary or secondary cutaneous immunity. Our work implies that myeloid APCs are a necessary source of IL-33 that drives acquired immunity against helminths, potentially through regulating gd T cell effector function(s). Ongoing studies seek to understand how myeloid APC derived IL-33 controls gd T cells to promote cutaneous immunity. NIH (R01 AI095289 and R01 GM083204) NSF GFRP

Host colonization with cutaneous commensal induces humoral immunity via formation of dermal tertiary lymphoid organs

Abstract The skin is one of the largest barrier sites which harbors a plethora of microorganisms. Whether skin microbiota promotes humoral responses remains unknown. Here we show that colonization with common skin commensal Staphylococcus epidermidis profoundly modulates cutaneous immunity that results in serum responsiveness with antigen-specific IgG antibodies. Such response is uncoupled from inflammatory signals and is associated with the induction of dermal tertiary lymphoid organs that closely resemble classical germinal centers. Of note, such responses occur in a tissue autonomous manner as evidenced by the preserved antibody repertoire in mice deficient in professional lymphoid organs. Our data also uncover a non-redundant role for Langerhan’s cells for the generation of commensal specific antibodies. Further, our work proposes a model by which commensal specific antigens are collected in the hair follicle leading to the generation of T follicular helper cells that further expand the local B cell pool in an IL-21-dependent manner. We also found that commensal induced antibodies can protect the host against subsequent infection with the same microbe demonstrating the importance of this line of defense in maintaining barrier protection. Collectively, our observations highlight the autonomous potential of skin organizational flexibility and for the first time demonstrate that B cells represent an indispensable local cutaneous compartment that actively maintains skin immunity.

Deciphering the crosstalk between skin commensals and the immune system.

Abstract The mechanisms underlying the crosstalk between the microbiota and the immune system remains largely unknown. We previously established that skin colonization with Staphylococcus epidermidisresults in the induction of T cell responses that control tissue function in a way that both enhances cutaneous immunity and promotes tissue repair. To uncover the molecular determinants of S. epidermidisthat stimulate T cells, we engineered a library of S. epidermidismutants with defined cell envelope alterations. Under physiological cutaneous colonization, we found that S. epidermidiscell envelope mutants elicit marked changes in the composition and function of the T cell populations in the skin. The removal of cell envelope lipoproteins and D-alanylation of teichoic acids almost completely abolished CD8 +T cell induction without significant effect on CD4 +T cell stimulation. Deletion of Tlr2gene also strongly reduced the CD8 +T cell response after S. epidermidiscolonization, while the CD4 +T cell response remained unchanged, a phenotype similar to the elimination of cell envelope lipoproteins and D-alanylation of teichoic acid in S. epidermidis. Furthermore, suprabasal keratinocytes express the highest level of TLR2 among keratinocyte subsets. Together, these results support the notion that the ability of S. epidermidisto induce CD8 +T cells is partially dependent on the host sensing of S. epidermidiswall teichoic acids and lipoprotein through TLR2. Using complementary strategies including novel mice models and imaging, current studies are focusing on deciphering on which cell population(s) TLR2 sensing of S. epidermidismolecular determinants is required for the induction of CD8 +T cell responses.

TP53 and its Regulatory Genes as Prognosis of Cutaneous Melanoma.

The present study was the first comprehensive investigation of genetic mutation and expression levels of the p53 signaling genes in cutaneous melanoma through various genetic databases providing large datasets. The mutational landscape of p53 and its signaling genes was higher than expected, with TP53 followed by CDKN2A being the most mutated gene in cutaneous melanoma. Furthermore, the expression analysis showed that TP53, MDM2, CDKN2A, and TP53BP1 were overexpressed, while MDM4 and CDKN2B were under-expressed in cutaneous melanoma. Overall, TCGA data revealed that among all the other p53 signaling proteins, CDKN2A was significantly higher in both sun and non-sun-exposed healthy tissues than in melanoma. Likewise, MDM4 and TP53BP1 expressions were markedly greater in non-sun-exposed healthy tissues compared to other groups. However, CDKN2B expression was higher in the sun-exposed healthy tissues than in other tissues. In addition, various genes were expressed significantly differently among males and females. In addition, CDKN2A was highly expressed in the SK-MEL-30 skin cancer cell line, whereas, Immune cell type expression analysis revealed that the MDM4 was highly expressed in naïve B-cells. Furthermore, all six genes were significantly overexpressed in extraordinarily overweight or obese tumor tissues compared to healthy tissues. MDM2 expression and tumor stage were closely related. There were differences in gene expression across patient age groups and positive nodal status. TP53 showed a positive correlation with B cells, MDM2 with CD8+T cells, macrophages and neutrophils, and MDM4 with neutrophils. CDKN2A/B had a non-significant correlation with all six types of immune cells. However, TP53BP1 was positively correlated with all five types of immune cells except B cells. Only TP53, MDM2, and CDKN2A had a role in cutaneous melanoma-specific tumor immunity. All TP53 and its regulating genes may be predictive for prognosis. The results of the present study need to be validated through future screening, in vivo, and in vitro studies.

005 IL-9 promotes a pathogenic phenotype and enhances proliferation in skin-tropic TH cells

IL-9 is a pleiotropic cytokine, for which an overarching role in humans remains elusive. Recent research shows that Interleukin 9 (IL-9) and its receptor, IL-9R, are predominantly expressed by skin-tropic T helper 2 (TH2) cells. This hence suggests that autocrine or paracrine IL-9 signals play an important role in cutaneous immunity and allergy. Yet, the mechanism of action remains incompletely understood. Here, we aimed at deciphering the effect of IL-9 on TH cells in allergic skin inflammation.

558 An aging-susceptible circadian rhythm controls cutaneous antiviral immunity

Aged skin is prone to viral infections, but the mechanisms responsible for this are unclear. We hypothesize that an aging circadian rhythm compromises cutaneous innate antiviral immunity. In support of this hypothesis, we observed that aged mammalian skin exhibits significant reduction in transcriptional levels of antiviral proteins (AVPs) and circadian transcriptional regulators including BMAL1 and CLOCK, in vivo and in vitro. Using BMAL1 and CLOCK knockout mouse models, we found that loss of circadian factors significantly reduces AVP expression in the skin.

Sprouty1 exerts a preventive effect on the initiation of psoriasis by inhibiting innate immune antimicrobial peptide cathelicidin and immunocytes

ObjectivesPsoriasis is an immune‐mediated skin disease dominated by the cutaneous immune system. Keratinocytes have been considered important triggers that initiate psoriasis. The key molecules and events of keratinocytes that link the innate immune system in psoriasis must be investigated in more detail. Human psoriasis skin and primary human keratinocyte were detected in vitro. Epidermis specific transgenic mouse strain (Krt14‐Sprouty1 tg) was used to further investigate psoriasis‐like skin inflammation in vivo.Materials and MethodsBulk RNA sequencing of primary human keratinocyte screened differentially expressed genes, which was confirmed by quantitative real time PCR and Western Blot (WB). Moreover, we concomitantly reviewed open‐accessed published RNAseq datasets of human psoriatic skin from GEO database. Immunohistochemical staining and immunofluorescence were used to detect Sprouty1 (SPRY1) expression in human psoriatic skin with and without anti‐psoriasis treatments. Krt14‐Sprouty1 tg was used to further investigate psoriasis‐like skin inflammation, and followed by Hematoxylin and Eosin (HE) Staining, enzyme linked immunosorbent assay (ELISA), Western Blot and flow cytometry.ResultsOur data showed that Sprouty1 was decreased in psoriatic skin and keratinocytes. In imiquimod‐induced psoriasis‐like skin inflammation, the production of cathelicidin (camp/LL37) was inhibited by suppressing signal transducer and activator of transcription3 (Stat3) activation when Sprouty1 overexpressed in mouse epidermal keratinocytes. Moreover, CD11b+CCR2+ dendritic cells, IL‐17A+ γδT cells, and Ly6C+ CD11c+ monocyte‐derived dendritic cells were decreased in Krt14‐Sprouty1 tg (STG) imiquimod‐induced cutaneous inflammation.ConclusionsThese findings indicate that Sprouty1 expressed in keratinocytes has a suppressive role in imiquimod‐induced skin inflammation mediated by inhibiting the production of cathelicidin. Collectively, Sprouty1 plays a preventive role in psoriatic skin. Our data provide new evidence for the pathogenesis of psoriatic keratinocytes, and the link cutaneous innate immunity, that indicated Sprouty1 is a potential novel therapeutic target.

Systemic lupus erythematosus patient on steroid therapy that develop to a Stevens-Johnson syndrome: a case report

Stevens-Johnson syndrome (SJS) is a cutaneous immunity reaction involving the skin and mucosa and is an emergency condition that can be fatal. The incidence of this disease is relatively rare in the range of 1-2 per 1.000.000 population. The pathogenesis of SJS involves the immune system response of antigenic drug to body tissues but it still cannot be fully explained to date. We reported a woman, 35 years old with systemic lupus erythematosus (SLE) who had been on steroid therapy and in the course of treatment developed into SJS after administration of anti-epileptic drug. Steroids have anti-inflammatory effects mainly due to decreased syntheses or suppression of inflammatory mediators. SJS still can develop in patient with SLE who had been on steroid therapy. Giving steroid that indicated for the treatment of a disease including SLE, cannot prevent the occurrence of an allergic event including SJS. The presence of steroid can extend the duration of starting the drug with the occurrence of SJS and reduce the severity of the disease. Steroid still have a role in treatment that can be used both in SJS and SLE.

Early age–related atrophy of cutaneous lymph nodes precipitates an early functional decline in skin immunity in mice with aging

Secondary lymphoid organs (SLOs) (including the spleen and lymph nodes [LNs]) are critical both for the maintenance of naive T (TN) lymphocytes and for the initiation and coordination of immune responses. How they age, including the exact timing, extent, physiological relevance, and the nature of age-related changes, remains incompletely understood. We used “time stamping” to indelibly mark newly generated naive T cells (also known as recent thymic emigrants) (RTEs) in mice, and followed their presence, phenotype, and retention in SLOs. We found that SLOs involute asynchronously. Skin-draining LNs atrophied by 6 to 9 mo in life, whereas deeper tissue-draining LNs atrophied by 18 to 20 mo, as measured by the loss of both TN numbers and the fibroblastic reticular cell (FRC) network. Time-stamped RTEs at all ages entered SLOs and successfully completed postthymic differentiation, but the capacity of older SLOs to maintain TN numbers was reduced with aging, and that trait did not depend on the age of TNs. However, in SLOs of older mice, these cells exhibited an emigration phenotype (CCR7loS1P1hi), which correlated with an increase of the cells of the same phenotype in the blood. Finally, upon intradermal immunization, RTEs generated in mice barely participated in de novo immune responses and failed to produce well-armed effector cells detectable in blood as early as by 7 to 8 mo of age. These results highlight changes in structure and function of superficial secondary lymphoid organs in laboratory mice that are earlier than expected and are consistent with the long-appreciated reduction of cutaneous immunity with aging.

Alarmin Cytokines as Central Regulators of Cutaneous Immunity.

Skin acts as the primary interface between the body and the environment. The skin immune system is composed of a complex network of immune cells and factors that provide the first line of defense against microbial pathogens and environmental insults. Alarmin cytokines mediate an intricate intercellular communication between keratinocytes and immune cells to regulate cutaneous immune responses. Proper functions of the type 2 alarmin cytokines, thymic stromal lymphopoietin (TSLP), interleukin (IL)-25, and IL-33, are paramount to the maintenance of skin homeostasis, and their dysregulation is commonly associated with allergic inflammation. In this review, we discuss recent findings on the complex regulatory network of type 2 alarmin cytokines that control skin immunity and highlight the mechanisms by which these cytokines regulate skin immune responses in host defense, chronic inflammation, and cancer.

CCR7-guided neutrophil redirection to skin-draining lymph nodes regulates cutaneous inflammation and infection.

Neutrophils are the first nonresident effector immune cells that migrate to a site of infection or inflammation; however, improper control of neutrophil responses can cause considerable tissue damage. Here, we found that neutrophil responses in inflamed or infected skin were regulated by CCR7-dependent migration and phagocytosis of neutrophils in draining lymph nodes (dLNs). In mouse models of Toll-like receptor-induced skin inflammation and cutaneous Staphylococcus aureus infection, neutrophils migrated from the skin to the dLNs via lymphatic vessels in a CCR7-mediated manner. In the dLNs, these neutrophils were phagocytosed by lymph node-resident type 1 and type 2 conventional dendritic cells. CCR7 up-regulation on neutrophils was a conserved mechanism across different tissues and was induced by a broad range of microbial stimuli. In the context of cutaneous immune responses, disruption of CCR7 interactions by selective CCR7 deficiency of neutrophils resulted in increased antistaphylococcal immunity and aggravated skin inflammation. Thus, neutrophil homing to and clearance in skin-dLNs affects cutaneous immunity versus pathology.

Regulation of Cutaneous Immunity In Vivo by Calcitonin Gene-Related Peptide Signaling through Endothelial Cells.

Calcitonin gene-related peptide (CGRP) can bias the outcome of Ag presentation to responsive T cells in vitro away from Th1-type immunity and toward the Th2 and Th17 poles through actions on endothelial cells (ECs). To test the in vivo significance of this observation, we engineered a mouse lacking functional CGRP receptors on ECs (EC receptor activity modifying protein 1 [RAMP1] knockout mice). On percutaneous immunization to 1-fluoro-2,4-dinitrobenzene, stimulated CD4+ T cells from draining lymph nodes showed significantly reduced IL-17A expression with significantly increased IFN-γ, IL-4, and IL-22 expression at the protein and mRNA levels compared with control mice. Retinoic acid receptor-related orphan receptor γ t mRNA was significantly reduced, while mRNAs for T-box expressed in T cells and GATA binding protein 3 were significantly increased. In addition, EC RAMP1 knockout mice had significantly reduced contact hypersensitivity responses, and systemic administration of a CGRP receptor antagonist similarly inhibited contact hypersensitivity in wild-type mice. These observations provide compelling evidence that CGRP is a key regulator of cutaneous immunity through effects on ECs and suggest a novel pathway for potential therapeutic manipulation.

Duration of NICU Exposure Associated With Decreased Risk of Atopic Dermatitis

To study the infant and environmental factors that may contribute to lowered incidence of atopic dermatitis (AD) in preterm infants.The study included infants born from June 1, 2011, to April 20, 2017, at the University of Florida.In this single-center retrospective study, researchers used electronic health records (EHRs). The study population was subdivided to those receiving primary care within the UF health system. Inclusion criteria were children who had at least 2 well-child visits, with 1 of the visits being at or after 300 days of life. The diagnosis of AD was determined if certain International Classification of Diseases, Ninth Revision, or International Classification of Diseases, 10th Revision, codes were used in the EHR record. Demographic, birth, maternal, and clinical information were extracted during EHR review. Independent samples t tests or χ2 tests were used to compare those with or without AD on continuous variables and categorical variables separately. The association of the predictor variables including sex, delivery mode, gestational age, birth weight, and length of stay in the NICU, with AD were examined by using logistic regression.Inclusion criteria was met by 4016 pairs of mother and infants. Nearly one-half (49%) of the infants were female. The distribution of race and ethnicity was as follows: 39.2% were Black, 38.5% were non-Hispanic White, 7.1% were Hispanic, and 15.2% were other race and ethnicities. The majority (65%) of deliveries were vaginal. A diagnosis of AD was made in 26.6% of the included study population. The incidence of AD was significantly associated with delivery mode (P = .13), NICU stay (P < .001), gestational age (P = .001), and birth weight (P = .002) in bivariate analysis. Longer gestation, vaginal delivery, no NICU stay, or higher birth weight were associated with an increased risk of developing AD. The lowest rates of AD were observed in extreme preterm infants (<28 weeks), and very preterm infants (28 to <32 weeks' gestation). When AD was modeled with the predictor variables, NICU length of stay was the only one to remain significantly (P = .004) associated with a lower risk of AD.A longer stay in the NICU correlated with a decreased risk of an infant developing AD.With this study, the authors provide a connection between NICU stay and incidence of AD development. This begs the question as to what factors associated with a NICU stay may contribute to this decreased incidence. In recent years, the human microbiome and its role in disease development have been at the forefront of novel research. Further exploration into the influence of NICU environmental exposures on cutaneous immunity as well as skin and intestinal microbiomes is warranted.

Metabolic and inflammatory biomarkers in children with atopic dermatitis (AD): a case-control study

BackgroundAtopic dermatitis is characterized by impaired skin barrier and altered cutaneous innate immunity. The estimated prevalence among Egyptian children was 10–12%. Several studies suggest that it may be associated with systemic comorbidities other than the spectrum of atopy, such as metabolic syndrome and other inflammatory conditions. The aim of this study is to compare the profile of systemic conditions of diabetes, dyslipidemia, and multiple inflammatory markers in children with and without diagnosed atopic dermatitis.MethodsOne hundred atopic dermatitis patients and 101 normal controls were collected from outpatient clinic based on their clinical condition, both had measurement of body mass index, blood sugar, serum insulin, lipid profile, C reactive protein, and gamma-glutamyl transferase.ResultsChildren diagnosed with atopic dermatitis had significantly higher levels of body mass index (34.7 ± 5.7 vs 26.1 ± 4.9), fasting glucose (143.2 ± 30.3 vs 100.8 ± 16.0), serum insulin (11.3 ± 4.4 vs. 4.6 ± 3.0), serum triglycerides (194.1 ± 38.1 vs 156.2 ± 31.6), total cholesterol (198.4 ± 27.7 vs 163.7 ± 27.7), alkaline phosphatase (229.4 ± 89.8 vs. 189.4 ± 46.8), and gamma-glutamyl transferase (54.7 ± 19.9 vs 34.3 ± 9.5), C-reactive protein level was approximately four times higher (19.9 ± 13.2 vs 5.1 ± 3.4) and the immunoglobulin E level was approximately 10 times higher (2050.3 ± 843.8 vs 252.7 ± 103.1) than in controlsConclusionWe found a positive relationship of atopic dermatitis with both diabetes and hyperlipidemia among children, and positive dose-response relationship of several non-traditional biomarkers of C-reactive protein, gamma-glutamyl transferase, and alkaline phosphatase with the presence and severity of atopic dermatitis.

008 Autocrine IL-9/IL-9Rα signaling induces a pathogenic phenotype in TH2 cells

IL-9 is a common gamma-chain cytokine, for which a range of pleiotropic functions have been proposed. However, an overarching role in humans remains elusive. IL-9 and its receptor, IL-9Rα, are specifically expressed by pathogenic TH2 cells (pTH2) residing in the skin, suggesting an important function of autocrine IL-9 signals in cutaneous immunity and allergy. Yet, the regulation of IL-9Rα expression on pTH2 cells and the auto- and paracrine functions of IL-9 remain incompletely understood. Here, we confirmed that IL-9Rα is strongly enriched in CRTh2+ memory TH2 cells isolated from blood and skin.

Skin microbiome dysbiosis in leprosy cases

&lt;p&gt;The human skin possesses a microenvironment conducive to the growth of the skin microbiome, which plays in many physiological functions in cutaneous immunity homeostasis and maturation. The microbiome composition depends on many variables, such as endogenous (host condition) or exogenous (environmental) factors and topographic location. Host-skin microbes’ interaction can be mutualism or pathogenicity. Dysbiosis or alteration in skin microbiota is associated with various dermatological diseases, including leprosy. Dysbiosis is driven by the alteration of the microbial communities themselves or due to the intrinsic features of the host. Leprosy is a chronic granulomatous disease caused by &lt;em&gt;Mycobacterium leprae&lt;/em&gt; targeting the nerves and skin, leading to loss of sensation on the skin, with or without dermatologic lesions, and correlated with long term consequences, such as deformities or disability. Microvascular dysfunction and significant alterations in capillary structure due to invasion of &lt;em&gt;M. leprae&lt;/em&gt; lead to altered hydration levels of the skin caused by disruption of blood flow; which changes the resident microbial community structure. The skin microbiome composition differences in leprosy patient’s skin lesions were observed; skin microbial diversity in the leprosy patients was lower than in healthy individuals. The diversity reduction was observed in freshly diagnosis leprosy patients, those at various stages of MDT, and post-MDT; indicated that both the interaction between skin microbial community and&lt;strong&gt; &lt;/strong&gt;&lt;em&gt;M. leprae&lt;/em&gt; or the ongoing therapeutic regimen impacted the skin microbiome variation. &lt;/p&gt;&lt;p&gt; &lt;/p&gt;

204 Age and circadian regulation of cutaneous innate antiviral immunity at homeostasis

204 Age and circadian regulation of cutaneous innate antiviral immunity at homeostasis

Cellular Senescence and Inflammaging in the Skin Microenvironment.

Cellular senescence and aging result in a reduced ability to manage persistent types of inflammation. Thus, the chronic low-level inflammation associated with aging phenotype is called “inflammaging”. Inflammaging is not only related with age-associated chronic systemic diseases such as cardiovascular disease and diabetes, but also skin aging. As the largest organ of the body, skin is continuously exposed to external stressors such as UV radiation, air particulate matter, and human microbiome. In this review article, we present mechanisms for accumulation of senescence cells in different compartments of the skin based on cell types, and their association with skin resident immune cells to describe changes in cutaneous immunity during the aging process.

Neu(ronal) custodians of cutaneous immunity

Sensory neurons have surfaced as key instigators of skin inflammation. In this issue of Cell, Zhang etal. define an anti-inflammatory Langerhans cell (LC)-neuron-mast cell (MC) circuit that underlies skin immune homeostasis. They uncover a role for LCs in maintaining innervation of MrgprD+ nonpeptidergic neurons that restrain MC activation via glutamate secretion.

Exogenous factors in the pathogenesis of atopic dermatitis: Irritants and cutaneous infections.

Atopic dermatitis (AD) is a chronic relapsing inflammatory cutaneous disease that is often associated with other atopic symptoms, such as food allergy, allergic rhinitis and asthma, leading to significant morbidity and healthcare costs. The pathogenesis of AD is complicated and multifactorial. Although the aetiology of AD remains incompletely understood, recent studies have provided further insight into AD pathophysiology, demonstrating that the interaction among genetic predisposition, immune dysfunction and environmental provocation factors contributes to its development. However, the increasing prevalence of AD suggests that environmental factors such as irritation and cutaneous infection play a crucial role in triggering and/or aggravating the disease. Of note, AD skin is susceptible to bacterial, fungal and viral infections, and microorganisms may colonize the skin and aggravate AD symptoms. Overall, understanding the mechanisms by which these risk factors affect the cutaneous immunity of patients with AD is of great importance for developing a precision medicine approach for treatment. This review summarizes recent developments in exogenous factors involved in the pathogenesis of AD, with special emphasis on irritants and microbial infections.