Up-regulation of the chemokine CCL21 in the skin of subjects exposed to irritants

Occupational Skin Dermatitis among Healthcare Workers Associated with the COVID-19 Pandemic: A Review of the Literature

The skin is the outermost layer of the human body and is continually exposed to numerous external stimuli, which can cause unwanted skin irritation. Occupational skin diseases are the most prevalent form of work-related illness and are found in a variety of sectors, particularly healthcare. During the recent COVID-19 pandemic, healthcare professionals experienced a variety of unexpected, unusual occupational skin diseases associated with COVID-19-engaged employment. Because the clinical characteristics of these types of skin inflammation are unique, this review focuses on the characteristics of a large category of occupational workers, namely COVID-19-engaged healthcare professionals. Furthermore, we examined the potential pathogeneses of occupational skin disorders associated with COVID-19-engaged labor, as well as different preventative methods.

SKIN FEATURES IMPORTANT FOR THE OCCURRENCE OF CONTACT DERMATITIS IN HEALTHCARE WORKERS

The occurrence of skin lesions in healthcare workers is associated with a negative impact on important skin functions, including protection from mechanical injuries, sunlight, dehydration, and penetration of chemical substances or pathogenic microorganisms. In healthcare professionals, the most common occupational skin disease is contact dermatitis (CD), either irritant (ICD) or allergic (ACD), and typically on the hands. ICD accounts for about 80% of occupational CD, making it the most frequent cause. According to the literature, CD frequency is higher among healthcare professionals than other occupations, with critical occupational risk factors including contact with irritants and allergens at the workplace. Furthermore, ICD is a multifactorial disorder influenced by many constituent and environmental factors. Constituent factors include age, gender, body location, atopy, and genetic factors, while environmental factors include temperature, airflow, humidity, and occlusion. Commonly encountered irritants are water, detergents and surfactants, solvents, oxidizing agents, acids, and alkalis; however, use of protective gloves or equipment, hand-washing habits, use of cleansers and creams, active inflammatory skin diseases, and daily activities are also important for ICD onset. Additionally, ICD is known to predispose to ACD. Important risk factors for ACD development include occupation, age, history of atopic dermatitis, genetics, female gender, and fair skin phototype. In summary, numerous skin features and other occupation-related factors contribute to CD among healthcare practitioners. Given the high level of exposure to contact irritants/allergens in the healthcare setting, implementation of preventive measures is crucial for a safer work environment.

Irritant Contact Dermatitis — a Review

Purpose of Review

Recent Findings

Summary

Genetic variants affecting chemical mediated skin immunotoxicity

The skin is an immune-competent organ and this function may be impaired by exposure to chemicals, which may ultimately result in immune-mediated dermal disorders. Interindividual variability to chemical-induced skin immune reactions is associated with intrinsic individual characteristics and their genomes. In the last 30-40 years, several genes influencing susceptibility to skin immune reactions were identified. The aim of this review is to provide information regarding common genetic variations affecting skin immunotoxicity. The polymorphisms selected for this review are related to xenobiotic-metabolizing enzymes (CYPA1 and CYPB1 genes), antioxidant defense (GSTM1, GSTT1, and GSTP1 genes), aryl hydrocarbon receptor signaling pathway (AHR and ARNT genes), skin barrier function transepidermal water loss (FLG, CASP14, and SPINK5 genes), inflammation (TNF, IL10, IL6, IL18, IL31, and TSLP genes), major histocompatibility complex (MHC) and neuroendocrine system peptides (CALCA, TRPV1, ACE genes). These genes present variants associated with skin immune responses and diseases, as well as variants associated with protecting skin immune homeostasis following chemical exposure. The molecular and association studies focusing on these genetic variants may elucidate their functional consequences and contribution in the susceptibility to skin immunotoxicity. Providing information on how genetic variations affect the skin immune system may reduce uncertainties in estimating chemical hazards/risks for human health in the future.

Mesenchymal stromal cells in wound healing applications: role of the secretome, targeted delivery and impact on recessive dystrophic epidermolysis bullosa treatment

Mesenchymal stromal cells (MSCs) are multi-potent stromal-derived cells capable of self-renewal that possess several advantageous properties for wound healing, making them of interest to the field of dermatology. Research has focused on characterizing the unique properties of MSCs, which broadly revolve around their regenerative and more recently discovered immunomodulatory capacities. Because of ease of harvesting and expansion, differentiation potential and low immunogenicity, MSCs have been leading candidates for tissue engineering and regenerative medicine applications for wound healing, yet results from clinical studies have been variable, and promising pre-clinical work has been difficult to reproduce. Therefore, the specific mechanisms of how MSCs influence the local microenvironment in distinct wound etiologies warrant further research. Of specific interest in MSC-mediated healing is harnessing the secretome, which is composed of components known to positively influence wound healing. Molecules released by the MSC secretome can promote re-epithelialization and angiogenesis while inhibiting fibrosis and microbial invasion. This review focuses on the therapeutic interest in MSCs with regard to wound healing applications, including burns and diabetic ulcers, with specific attention to the genetic skin disease recessive dystrophic epidermolysis bullosa. This review also compares various delivery methods to support skin regeneration in the hopes of combating the poor engraftment of MSCs after delivery, which is one of the major pitfalls in clinical studies utilizing MSCs.

In Sickness and in Health: The Immunological Roles of the Lymphatic System

The lymphatic system plays crucial roles in immunity far beyond those of simply providing conduits for leukocytes and antigens in lymph fluid. Endothelial cells within this vasculature are distinct and highly specialized to perform roles based upon their location. Afferent lymphatic capillaries have unique intercellular junctions for efficient uptake of fluid and macromolecules, while expressing chemotactic and adhesion molecules that permit selective trafficking of specific immune cell subsets. Moreover, in response to events within peripheral tissue such as inflammation or infection, soluble factors from lymphatic endothelial cells exert “remote control” to modulate leukocyte migration across high endothelial venules from the blood to lymph nodes draining the tissue. These immune hubs are highly organized and perfectly arrayed to survey antigens from peripheral tissue while optimizing encounters between antigen-presenting cells and cognate lymphocytes. Furthermore, subsets of lymphatic endothelial cells exhibit differences in gene expression relating to specific functions and locality within the lymph node, facilitating both innate and acquired immune responses through antigen presentation, lymph node remodeling and regulation of leukocyte entry and exit. This review details the immune cell subsets in afferent and efferent lymph, and explores the mechanisms by which endothelial cells of the lymphatic system regulate such trafficking, for immune surveillance and tolerance during steady-state conditions, and in response to infection, acute and chronic inflammation, and subsequent resolution.

Chemokines during anaphylaxis: the importance of CCL2 and CCL2-dependent chemotactic activity for basophils

Background

The role of chemokines in anaphylaxis is unclear.

Methods

We prospectively recruited 49 patients presenting to the emergency department with an acute episode of anaphylaxis and 28 healthy subjects. We measured serum levels of the chemokines CCL2, CCL5, CCL7, CCL8, CCL11, CCL13, CCL17, CCL21, CCL22, CCL24, and CCL26, tryptase, the absolute number of circulating basophils, monocytes, lymphocytes, and PMNs, and whole blood FCER1A, CPA3 and HDC gene expression at two time points: during the anaphylactic episode and in convalescent samples collected approximately 3 months later. We then investigated the in vitro chemotactic activity of chemokines induced during anaphylaxis for the in vitro migration of the corresponding cells.

Results

Only CCL2 chemokine levels were significantly increased in anaphylaxis samples (median 514 pg/ml) compared to convalescent samples (284 pg/ml, P < 0.0001) and healthy subjects (279 pg/ml, P < 0.0001); there was no significant difference in any of the other chemokines. There was a significant positive correlation between the rates of increase of serum CCL2 (median [range]: 106.0% [− 44.7% to 557.4%]) and tryptase (133.8% [− 6.6% to 893.4%]; r = 0.68, P < 0.0001) and between the acute concentration of serum CCL2 and the acute concentration of serum tryptase (r = 0.77, P < 0.0001). The number of circulating basophils, but not other blood cells, significantly decreased during anaphylaxis (median 5.0 vs. 19.1 cells/µl in convalescent samples; P < 0.0001); a decrease in whole-blood gene expression of basophil markers (P ≤ 0.0018) confirmed these changes. Anaphylactic serum enhances the in vitro migration of basophils via CCL2-dependent chemotactic activity; in contrast, no CCL2-dependent chemotactic activity was observed for convalescent samples.

Conclusions

Our findings imply an important and specific role for CCL2-mediated chemotactic activity in the pathophysiology of human anaphylaxis.

Keratinocyte-specific deletion of the IL-6RΑ exacerbates the inflammatory response during irritant contact dermatitis

Irritant Contact Dermatitis (ICD) is the most common occupational skin disorder. During ICD, keratinocytes initiate the inflammatory cascade by producing cytokines including IL-6. This laboratory previously reported that IL-6 deficiency exacerbates skin inflammation during ICD, yet the role of the IL-6Rα in keratinocyte function has yet to be elucidated. To investigate how IL-6Rα function in keratinocytes influences the inflammatory response during ICD, keratinocyte-specific IL-6Rα KO (IL6ra^Δker) and WT mice were exposed to two well-known occupational irritants; JP-8 jet fuel, and benzalkonium chloride (BKC), or acetone control for three days. Dermatitis lesions were collected and flow cytometric and immunohistochemical analyses revealed that IL6ra^Δker skin displayed increased populations of CD11b⁺CD45⁺ and F4/80⁺ cells respectively relative to WT. However, IL6ra^Δker mouse skin contained reduced numbers of γδ T cells relative to WT. Furthermore, IL6ra^Δker skin expressed increased levels of pro-inflammatory cytokines including IL-1β, IL-22, and CCL4 but decreased levels of anti-inflammatory cytokines IL-4 and IL-10. These results indicate that epidermal keratinocyte IL-6Rα function modulates epidermal hyperplasia, immune cell infiltration into skin and cytokine expression during ICD and suggests that the previously reported protective effect of IL-6 during ICD might be mediated primarily by keratinocyte derived IL-6Rα.

Leucocyte Trafficking via the Lymphatic Vasculature- Mechanisms and Consequences

The lymphatics fulfill a vital physiological function as the conduits through which leucocytes traffic between the tissues and draining lymph nodes for the initiation and modulation of immune responses. However, until recently many of the molecular mechanisms controlling such migration have been unclear. As a result of careful research, it is now apparent that the process is regulated at multiple stages from initial leucocyte entry and intraluminal crawling in peripheral tissue lymphatics, through to leucocyte exit in draining lymph nodes where the migrating cells either participate in immune responses or return to the circulation via efferent lymph. Furthermore, it is increasingly evident that most if not all leucocyte populations migrate in lymph and that such migration is not only important for immune modulation, but also for the timely repair and resolution of tissue inflammation. In this article, I review the latest research findings in these areas, arising from new insights into the distinctive ultrastructure of lymphatic capillaries and lymph node sinuses. Accordingly, I highlight the emerging importance of the leucocyte glycocalyx and its novel interactions with the endothelial receptor LYVE-1, the intricacies of endothelial chemokine secretion and sequestration that direct leucocyte trafficking and the significance of the process for normal immune function and pathology.

A Novel S100A8/A9 Induced Fingerprint of Mesenchymal Stem Cells associated with Enhanced Wound Healing

We here investigated whether the unique capacity of mesenchymal stem cells (MSCs) to re-establish tissue homeostasis depends on their potential to sense danger associated molecular pattern (DAMP) and to mount an adaptive response in the interest of tissue repair. Unexpectedly, after injection of MSCs which had been pretreated with the calcium-binding DAMP protein S100A8/A9 into murine full-thickness wounds, we observed a significant acceleration of healing even exceeding that of non-treated MSCs. This correlates with a fundamental reprogramming of the transcriptome in S100A8/A9 treated MSCs as deduced from RNA-seq analysis and its validation. A network of genes involved in proteolysis, macrophage phagocytosis, and inflammation control profoundly contribute to the clean-up of the wound site. In parallel, miR582-5p and genes boosting energy and encoding specific extracellular matrix proteins are reminiscent of scar-reduced tissue repair. This unprecedented finding holds substantial promise to refine current MSC-based therapies for difficult-to-treat wounds and fibrotic conditions.

Assessment of pulmonary 18F-FDG-PET uptake and cytokine profiles in non-small cell lung cancer patients treated with radiotherapy and erlotinib

Purpose

To investigate effects of radiotherapy (RT) and erlotinib on pulmonary glucose uptake using 2-deoxy-2-(18F)fluoro-D-glucose (¹⁸F-FDG) positron emission tomography (PET) during and after treatment of non-small cell lung cancer (NSCLC) and to identify associations between serum cytokine levels and lung glucose uptake.

Material and methods

Twenty-seven patients with advanced NSCLC, receiving RT alone or concomitant RT and erlotinib therapy, were examined by ¹⁸F-FDG PET before, during, and after treatment. A total of 57 ¹⁸F-FDG PET scans were analyzed. Pulmonary ¹⁸F-FDG uptake and radiotherapy dose mapping were used to acquire dose-response curves for each patient, where subsequent linear regression gave a glucose uptake level in the un-irradiated parts of the lungs (SUV₀) and a response slope (ΔSUV). Serum cytokine levels at corresponding time points were assessed using a multiplex bioassay. Correlations between the most robust cytokines and lung ¹⁸F-FDG dose response parameters were further investigated.

Results

From the dose response analysis, SUV₀ at post-therapy was significantly higher (P < 0.001) than at mid- and pre-therapy (45% and 58%, respectively) for the group receiving RT + erlotinib. Also, SUV₀ at post-therapy was higher for patients receiving RT + erlotinib compared to RT alone (42%; P < 0.001). No differences in ΔSUV were seen with treatments or time. SUV₀ was positively associated (r = 0.47, P = 0.01) with serum levels of the chemokine C-C motif ligand 21 (CCL21) for patients receiving RT + erlotinib.

Conclusions

Concomitant RT and erlotinib causes an elevation in pulmonary ¹⁸F-FDG uptake post treatment compared to RT alone. Pulmonary glucose uptake is associated with an upregulation of a chemokine (CCL21) involved in inflammatory reactions.

Inhibition of EGFR Tyrosine Kinase by Erlotinib Prevents Sclerodermatous Graft-Versus-Host Disease in a Mouse Model

Chronic graft-versus-host disease (GVHD) follows allogeneic hematopoietic stem cell transplantation. It results from alloreactive processes induced by minor histocompatibility antigen incompatibilities leading to the activation of CD4 T cells and the development of fibrosis and inflammation of the skin and visceral organs and autoimmunity that resemble systemic sclerosis. EGFR is a ubiquitous cell receptor deeply involved in cell proliferation, differentiation, and motility. EGFR has recently been implicated in autoimmune and fibrotic diseases. Therefore, we tested whether Erlotinib, an EGFR tyrosine kinase inhibitor, can prevent sclerodermatous GVHD (Scl-GVHD). Scl-GVHD was induced in BALB/c mice by B10.D2 bone marrow and spleen cell transplantation. Transplanted mice displayed severe clinical symptoms including alopecia, fibrosis of the skin and visceral organs, vasculitis, and diarrhea. The symptoms were reversed in mice treated with Erlotinib. These beneficial effects were mediated by the decreased production of activated/memory CD4(+) T cells and the reduction in T-cell infiltration of the skin and visceral organs along with a decrease in IFN-γ and IL-13 production and autoimmune B-cell activation. The improvement provided by Erlotinib in the mouse model of Scl-GVHD supplies a rationale for the evaluation of Erlotinib in the management of patients affected by chronic GVHD.

CXCR4 is dispensable for T cell egress from chronically inflamed skin via the afferent lymph

T cell recirculation through extralymphoid tissues is essential to immune surveillance, host defense and inflammation. In this process, T cells enter the tissue from the blood and subsequently leave via the afferent lymph. In the absence of inflammation, T cells require CCR7 expression to egress from the skin or lung, which is consistent with the constitutive expression of the CCR7 ligand CCL21 on lymphatic endothelium. However, during chronic inflammation alternative chemoattractants come into play, allowing Ccr7-deficient (Ccr7^−/−) T cells to egress efficiently from affected skin. As T cell egress from inflamed sites is a potential control point of the inflammatory response, we aimed to determine alternative T cell exit receptors using a mouse and a sheep model. We show that CCR7⁺ and CCR7^– T cells exiting from the chronically inflamed skin were highly responsive to the CXCR4 ligand CXCL12, which was induced in the lymphatics in the inflamed site. Based on these findings, we hypothesized that CXCR4 mediates T cell egress from inflamed skin. However, pharmacological inhibition of CXCR4 did not affect the tissue egress of wildtype or Ccr7^−/− CD4 and CD8 T cells after adoptive transfer into chronically inflamed skin. Similarly, adoptively transferred Cxcr4^−/− Ccr7^−/− and Ccr7^−/− T cells egressed from the inflamed skin equally well. Based on these data, we conclude that, while CXCR4 might play an essential role for other cell types that enter the afferent lymphatics, it is dispensable for T cell egress from the chronically inflamed skin.

Cytokines and chemokines in irritant contact dermatitis

Irritant contact dermatitis is a result of activated innate immune response to various external stimuli and consists of complex interplay which involves skin barrier disruption, cellular changes, and release of proinflammatory mediators. In this review, we will focus on key cytokines and chemokines involved in the pathogenesis of irritant contact dermatitis and also contrast the differences between allergic contact dermatitis and irritant contact dermatitis.

Immune functions of the skin

The skin, the body's largest organ, helps to secure the integrity of the host and, at the same time, allows the individual to communicate with the outside world. This finely tuned balance between protection from harmful pathogens (mostly microorganisms) and bidirectional signal exchange is provided by a network of structural, cellular, and molecular elements that are collectively referred to as the skin barrier. This "gateway" has a physical, chemical, and immunologic component. The role of the latter is to elicit a powerful defense reaction in the case of danger and, at the same time, to prevent such a reaction against innocuous substances. Immune responses originating in the skin are mounted and executed by cells and molecules of the innate or the adaptive immune system. Innate reactions are typically rapid, poorly discriminating, and do not exhibit memory. Adaptive responses, in contrast, show a high degree of specificity as well as memory but need a protracted time for their development. As a consequence, innate and adaptive responses are consecutive events influencing each other. In fact, we now know that the type and magnitude of the innate reactions govern and often determine the quality and quantity of adaptive responses.

Tissue inflammation modulates gene expression of lymphatic endothelial cells and dendritic cell migration in a stimulus-dependent manner

Chemokines and adhesion molecules up-regulated in lymphatic endothelial cells (LECs) during tissue inflammation are thought to enhance dendritic cell (DC) migration to draining lymph nodes, but the in vivo control of this process is not well understood. We performed a transcriptional profiling analysis of LECs isolated from murine skin and found that inflammation induced by a contact hypersensitivity (CHS) response up-regulated the adhesion molecules ICAM-1 and VCAM-1 and inflammatory chemokines. Importantly, the lymphatic markers Prox-1, VEGFR3, and LYVE-1 were significantly down-regulated during CHS. By contrast, skin inflammation induced by complete Freund adjuvant induced a different pattern of chemokine and lymphatic marker gene expression and almost no ICAM-1 up-regulation in LECs. Fluorescein isothiocyanate painting experiments revealed that DC migration to draining lymph nodes was more strongly increased in complete Freund adjuvant-induced than in CHS-induced inflammation. Surprisingly, DC migration did not correlate with the induction of CCL21 and ICAM-1 protein in LECs. Although the requirement for CCR7 signaling became further pronounced during inflammation, CCR7-independent signals had an additional, albeit moderate, impact on enhancing DC migration. Collectively, these findings indicate that DC migration in response to inflammation is stimulus-specific, mainly CCR7-dependent, and overall only moderately enhanced by LEC-induced genes other than CCL21.

Blocking MAPK signaling downregulates CCL21 in lymphatic endothelial cells and impairs contact hypersensitivity responses

CCL21 expression by lymphatic endothelial cells (LECs) is essential for migration of CCR7+ immune cells from skin to regional lymph nodes (LNs). We investigated the importance of mitogen-activated protein kinase (MAPK) signaling in CCL21 expression by ECs in vitro and in vivo. Normal human dermal lymphatic microvascular ECs (HMVEC-dLy) stimulated in vitro with oncostatin M (OSM) expressed high amounts of CCL21 mRNA. CCL21 protein expression by HMVEC-dLy was also markedly increased by OSM compared with unstimulated cultures. Marked phosphorylation of MAPK 44/42 was detected in HMVEC-dLy stimulated by OSM. CCL21 expression by HMVEC-dLy was blocked by a JAK inhibitor 1, JAK3 inhibitor, and U0126 (a MAPK kinase inhibitor) in vitro, all of which blocked phosphorylation of MAPK 44/42. In addition, injection of U0126 into murine skin significantly decreased CCL21 mRNA and protein expression. Moreover, injection of U0126 before sensitization decreased migration of dendritic cells to draining LNs and decreased contact hypersensitivity responses. In summary, these results suggest that the MAPK pathway is important for CCL21 expression by LECs in vitro and in vivo. Blocking MAPK signaling within skin may offer a novel approach to treatment of inflammatory skin diseases.

Contact dermatitis in older adults: a review of the literature

Contact dermatitis is a significant health problem affecting the elderly. Impaired epidermal barrier function and delayed cutaneous recovery after insult enhances susceptibility to both irritants and allergens. Exposure to more numerous potential sensitizers and for greater durations influences the rate of allergic contact dermatitis in this population. Medical co-morbidities, including stasis dermatitis and venous ulcerations, further exacerbate this clinical picture. However, while these factors tend to increase the degree of sensitization in the elderly, waning immunity can actually decrease such a propensity. This interplay of both intrinsic and extrinsic factors makes a generalization on trends for contact dermatitis in older adults challenging. The literature has varying reports on the overall incidence of allergic contact dermatitis with advancing age. Nevertheless, it does clearly show that sensitivity to topical medicaments increases with age. Irritant contact dermatitis studies are more consistent, with less reactivity (to irritants) in older compared with younger skin. Diagnosis of both irritant and allergic contact dermatitis is based on a thorough history, complete skin examination, and comprehensive patch testing. The mainstay of therapy is avoidance of the offending chemical substances and the use of topical along with systemic therapies, depending on the severity of the condition.

Accumulation and local proliferation of antigen-specific CD4+ T cells in antigen-bearing tissue

Although activation and subsequent expansion of naive CD4(+) T cells within lymph nodes is well characterized, the fate of T effector cells activated within peripheral tissues during secondary reactions is poorly defined. Therefore, we studied the recruitment, proliferation and egress of antigen-specific Th1 effector cells in comparison with nonspecific Th1 cells throughout a delayed-type hypersensitivity reaction (DTH). Although we observed a high turnover of Th1 effector cells with unspecific high-rate recruitment and CCR7-dependent egress from the inflamed tissue in the early, acute DTH phase, a strong, selective accumulation of antigen-specific T cells occurred during the chronic, late DTH phase. This was mainly based on local proliferation of CD4(+) effector cells within the DTH tissue and concomitant retention. Considering the strong CCR7-dependent Th cell egress found in this model, the reduced CCR7 expression on antigen-specific T cells isolated from late-phase DTH tissue most likely contributes to the retention of these cells within the tissue. Thus, peripheral tissues can support not only the proliferation of CD8(+) T cells, as recently shown, but also that of CD4(+) T effector cells, forming a pool of tissue-resident T cells.

Chemoattractant receptors and lymphocyte egress from extralymphoid tissue: changing requirements during the course of inflammation

Memory/effector T cells traffic efficiently through extralymphoid tissues, entering from the blood and leaving via the afferent lymph. During inflammation, T cell traffic into the affected tissue dramatically increases; however, the dynamics and mechanisms of T cell exit from inflamed tissues are poorly characterized. In this study, we show, using both a mouse and a sheep model, that large numbers of lymphocytes leave the chronically inflamed skin. Many T cells capable of producing IFN-γ and IL-17 also entered the draining afferent lymph, demonstrating that memory/effector T cells egress from sites of inflammation. Whereas efficient egress from acutely inflamed skin required lymphocyte-expressed CCR7, chronic inflammation promoted significant CCR7-independent exit as well. Lymphocyte exit at late time points of inflammation was sensitive to pertussis toxin but was only partially affected by the drug FTY720, implying the contribution of alternative chemoattractant receptors other than spingosine 1-phosphate receptor 1. Our data show that CCR7 is an important receptor for lymphocyte egress from both resting and inflamed extralymphoid tissues, but that alternative exit receptors come into play during chronic inflammation.

Induction and effector phase of allergic lung inflammation is independent of CCL21/CCL19 and LT-beta

The chemokines CCL21 and CCL19, and cell bound TNF family ligand lymphotoxin beta (LTbeta), have been associated with numerous chronic inflammatory diseases. A general role in chronic inflammatory diseases cannot be assumed however; in the case of allergic inflammatory disease, CCL21/CCL19 and LTbeta have not been associated with the induction, recruitment, or effector function of Th2 cells nor dendritic cells to the lung. We have examined the induction of allergic inflammatory lung disease in mice deficient in CCL21/CCL19 or LTbeta and found that both kinds of mice can develop allergic lung inflammation. To control for effects of priming differences in knockout mice, adoptive transfers of Th2 cells were also performed, and they showed that such effector cells had equivalent effects on airway hyper-responsiveness in both knockout background recipients. Moreover, class II positive antigen presenting cells (B cells and CD11c+ dendritic cells) showed normal recruitment to the peribronchial spaces along with CD4 T cells. Thus, the induction of allergic responses and recruitment of both effector Th2 cells and antigen presenting cells to lung peribronchial spaces can develop independently of CCL21/CCL19 and LTbeta.

Pattern of proinflammatory cytokine induction in RAW264.7 mouse macrophages is identical for virulent and attenuated Borrelia burgdorferi

Lyme disease pathogenesis results from a complex interaction between Borrelia burgdorferi and the host immune system. The intensity and nature of the inflammatory response of host immune cells to B. burgdorferi may be a determining factor in disease progression. Gene array analysis was used to examine the expression of genes encoding cytokines, chemokines, and related factors in the joint tissue of infected C3H/HeJ mice and in a murine macrophage-like cell line in response to a disseminating or attenuated clinical isolate of B. burgdorferi. Both isolates elicited a robust proinflammatory response in RAW264.7 cells characterized by an increase in transcript levels of genes encoding CC and CXC chemokines, proinflammatory cytokines, and TNF superfamily members. Transcription of genes encoding IL-1beta, IL-6, MCP-1, MIP-1alpha, CXCR4, and TLR2 induced in RAW264.7 cells by either live or heat-killed spirochetes did not differ significantly at any time point over a 24-h period, nor was there a difference in the protein levels of IL-10, TNF-alpha, IL-6, and IL-12p70 in culture supernatants. Thus, induction of host macrophage expression of proinflammatory mediators by host macrophages does not contribute to the differential pathogenicity of different B. burgdorferi strains.

Markers for microscopic imaging of lymphangiogenesis and angiogenesis

Imaging of lymphangiogenesis and angiogenesis requires robust and unambiguous markers of lymphatic and blood vessels. Although much progress has been made in recent years in identifying molecules specifically expressed on lymphatic and blood vessels, no perfect marker has been found that works reliably in all species, tissues, vascular beds, and in all physiological and pathologic conditions. The heterogeneity of expression of markers in both blood and lymphatic vessels reflects underlying differences in the phenotype of endothelial cells. Use of only one marker can lead to misleading interpretations, but these pitfalls can usually be avoided by use of multiple markers and three-dimensional whole-mount preparations. LYVE-1, VEGFR-3, Prox1, and podoplanin are among the most useful markers for microscopic imaging of lymphatic vessels, but, depending on histologic location, each marker can be expressed by other cell types, including vascular endothelial cells. Other markers, including CD31, junctional proteins, and receptors, such as VEGF-2, are shared by lymphatic and blood vessels.

Skin irritation and sensitization: mechanisms and new approaches for risk assessment. 1. Skin irritation

Cutaneous irritation presents a major health problem with serious social and occupational impact. The interaction between an irritant and the human skin depends on multiple factors: the intrinsic properties and the nature of the irritant itself, and specific individual- and environment-related variables. The main pathological mechanisms of irritancy include skin barrier disruption, induction of a cytokine cascade and involvement of the oxidative stress network; all of them resulting in a visible or subclinical inflammatory reaction. In vivo, different non-invasive parameters for the evaluation of skin irritation and irritant potential of compounds and their specific formulations have been introduced, such as epidermal barrier function, skin hydration, surface pH, lipid composition, skin colour and skin blood flow. The diverse physiological changes caused by irritating agents require implementation of a multiparametric approach in the evaluation of cutaneous irritancy.

Gene Expression Time Course in the Human Skin during Elicitation of Allergic Contact Dermatitis

Genes involved in the inflammatory response resulting in allergic contact dermatitis (ACD) are only partly known. In this study, we introduce the use of high-density oligonucleotide arrays for gene expression profiling in human skin during the elicitation of ACD. Skin biopsies from normal and nickel-exposed skin were obtained from seven nickel-allergic patients and five nonallergic controls at four different time points during elicitation of eczema. Each gene expression profile was analyzed by hybridization to high-density oligonucleotide arrays. Cluster analysis of 74 genes found to be differentially expressed in the patients over time revealed that the patient samples may be categorized into two groups: an early time-point group (no clinical reaction) and a late time-point group (clinical reaction). Bioinformatics analyses unraveled the potential involvement of signal transducers and activator of transcription and small/mothers against decepentaplegic (SMAD) transcription factors in the late time-point gene expression patterns. Concerning specific genes, the homeostatic chemokine CCL19 was unexpectedly found to be highly expressed in cells scattered in the deep dermis of the late time-point samples. Taken together, these findings suggest hitherto unknown roles of SMAD transcription factors and of CCL19 in the elicitation phase of ACD.

Chemokine receptor CCR7 required for T lymphocyte exit from peripheral tissues

Lymphocytes travel throughout the body to carry out immune surveillance and participate in inflammatory reactions. Their path takes them from blood through tissues into lymph and back to blood. Molecules that control lymphocyte recruitment into extralymphoid tissues are well characterized, but exit is assumed to be random. Here, we showed that lymphocyte emigration from the skin was regulated and was sensitive to pertussis toxin. CD4(+) lymphocytes emigrated more efficiently than CD8(+) or B lymphocytes. T lymphocytes in the afferent lymph expressed functional chemokine receptor CCR7, and CCR7 was required for T lymphocyte exit from the skin. The regulated expression of CCR7 by tissue T lymphocytes may control their exit, acting with recruitment mechanisms to regulate lymphocyte transit and accumulation during immune surveillance and inflammation.

Cytokine polymorphisms in patients with pemphigus

The aim of this study was to assess whether tumor necrosis factor alpha (TNF-alpha), transforming growth factor beta1 (TGF-beta1) and interleukin-10 (IL-10) polymorphisms are among the factors influencing the development of pemphigus. Whole blood from 20 patients with pemphigus and 24 control subjects was taken. Genomic DNA was obtained and cytokine genotyping for IL-10 (-1082 G/A; -819 C/T), TGFB1 (codon 10 C/T, codon 25 G/C) and TNFA (-308 G/A) was performed using the ARMS-PCR method. The distribution of IL-10 (-819) alleles was significantly different between the pemphigus and control groups (P=0.009). In particular, allele T was associated with the disease (OR 3.291, 95% CI 1.350-8.020). Similar results were observed when only pemphigus vulgaris (PV) patients were analyzed (P=0.012, OR 3.410, 95% CI 1.346-8.639). An increased frequency of the low producer IL-10 haplotype (-1082/-819 A/T) in patients with pemphigus compared with controls was observed (OR 2.714, 95% CI 1.102-6.685) and this association was also significant when only PV patients were considered (OR 2.667, 95% CI 1.043-6.816). There were no differences between patients and controls in the frequency of any other gene polymorphism analyzed. The increased frequency of the low producer IL-10 haplotype (-1082 /-819 A/T) suggest that the carriage of this haplotype might predispose to pemphigus or the high and intermediate producer haplotypes may be protective factors. The prevalence of the allele IL-10 (-819 T) in pemphigus patients cannot be explained by the current hypothesis, according to which a particular allele of the gene is associated with a different level of cytokine production and therefore affects the predisposition to a particular disease. However, this cytokine polymorphism might be linked to an unknown susceptibility factor.