Bacterial superantigens induce T cell expression of the skin-selective homing receptor, the cutaneous lymphocyte-associated antigen, via stimulation of interleukin 12 production

Triggers for the onset and recurrence of psoriasis: a review and update

Psoriasis is an immune-mediated inflammatory skin disease, involving a complex interplay between genetic and environmental factors. Previous studies have demonstrated that genetic factors play a major role in the pathogenesis of psoriasis. However, non-genetic factors are also necessary to trigger the onset and recurrence of psoriasis in genetically predisposed individuals, which include infections, microbiota dysbiosis of the skin and gut, dysregulated lipid metabolism, dysregulated sex hormones, and mental illness. Psoriasis can also be induced by other environmental triggers, such as skin trauma, unhealthy lifestyles, and medications. Understanding how these triggers play a role in the onset and recurrence of psoriasis provides insights into psoriasis pathogenesis, as well as better clinical administration. In this review, we summarize the triggers for the onset and recurrence of psoriasis and update the current evidence on the underlying mechanism of how these factors elicit the disease. Video Abstract.

CLA+ memory T cells in atopic dermatitis: CLA+ T cells and atopic dermatitis

Circulating skin-homing cutaneous lymphocyte-associated antigen (CLA)+ T cells constitute a small subset of human memory T cells involved in several aspects of atopic dermatitis: Staphylococcus aureus related mechanisms, the abnormal Th2 immune response, biomarkers, clinical aspects of the patients, pruritus, and the mechanism of action of targeted therapies. Superantigens, IL-13, IL-31, pruritus, CCL17 and early effects on dupilumab-treated patients have in common that they are associated with the CLA+ T cell mechanisms in atopic dermatitis patients. The function of CLA+ T cells corresponds with the role of T cells belonging to the skin-associated lymphoid tissue and could be a reason why they reflect different mechanisms of atopic dermatitis and many other T cell mediated skin diseases. The goal of this review is to gather all this translational information of atopic dermatitis pathology.

Allergen sensitization stratifies IL-31 production by memory T cells in atopic dermatitis patients

Background

The role of allergen sensitization in IL-31 production by T cells and specifically in the clinical context of atopic dermatitis (AD) has not been characterized.

Methods

The response to house dust mite (HDM) in purified memory T cells cocultured with epidermal cells from AD patients (n=58) and control subjects (n=11) was evaluated. AD-associated cytokines from culture supernatants, plasma proteins and mRNA expression from cutaneous lesions were assessed and related with the clinical features of the patients.

Results

HDM-induced IL-31 production by memory T cells defined two subsets of AD patients according to the presence or absence of IL-31 response. Patients in the IL-31 producing group showed a more inflammatory profile, and increased HDM-specific (sp) and total IgE levels compared to the IL-31 non-producing group. A correlation between IL-31 production and patient’s pruritus intensity, plasma CCL27 and periostin was detected. When the same patients were analyzed based on sp IgE and total IgE levels, an increased IL-31 in vitro response, as well as type 2 markers in plasma and cutaneous lesions, was found in patients with sp IgE levels > 100 kUA/L and total IgE levels > 1000 kU/L. The IL-31 response by memory T cells was restricted to the cutaneous lymphocyte-associated antigen (CLA)+ T-cell subset.

Conclusion

IgE sensitization to HDM allows stratifying IL-31 production by memory T cells in AD patients and relating it to particular clinical phenotypes of the disease.

Roles of Infection in Psoriasis

Psoriasis is a chronic, immune-mediated disorder with cutaneous and systemic manifestations. Genetic predisposition, environmental factors, and immune dysfunction all contribute to the pathogenesis of psoriasis with host-microbe interaction governing the progression of this disease. Emerging evidence has indicated that infection is an environmental trigger for psoriasis and plays multiple roles in its maintenance as evidenced by the frequent association between guttate psoriasis onset and acute streptococcal infection. Different infectious factors act on immune cells to produce inflammatory cytokines that can induce or aggravate psoriasis. In addition to bacterial infections, viral and fungal infections have also been shown to be strongly associated with the onset or exacerbation of psoriasis. Intervention of skin microbiota to treat psoriasis has become a hot research topic. In this review, we summarize the effects of different infectious factors (bacteria, viruses, and fungi) on psoriasis, thereby providing insights into the manipulation of pathogens to allow for the identification of improved therapeutic options for the treatment of this condition.

Update on molecular diversity and multipathogenicity of staphylococcal superantigen toxins

Staphylococcal superantigen (SAg) toxins are the most notable virulence factors associated with Staphylococcus aureus, which is a pathogen associated with serious community and hospital acquired infections in humans and various diseases in animals. Recently, SAg toxins have become a superfamily with 29 types, including staphylococcal enterotoxins (SEs) with emetic activity, SE-like toxins (SEls) that do not induce emesis in primate models or have yet not  been tested, and toxic shock syndrome toxin-1 (TSST-1). SEs and SEls can be subdivided into classical types (SEA to SEE) and novel types (SEG to SElY, SE01, SE02, SEl26 and SEl27). The genes of SAg toxins are located in diverse accessory genetic elements and share certain structural and biological properties. SAg toxins are heat-stable proteins that exhibit pyrogenicity, superantigenicity and capacity to induce lethal hypersensitivity to endotoxin in humans and animals. They have multiple pathogenicities that can interfere with normal immune function of host, increase the chances of survival and transmission of pathogenic bacteria in host, consequently contribute to the occurrence and development of various infections, persistent infections or food poisoning. This review focuses on the following aspects of SAg toxins: (1) superfamily members of classic and novelty discovered staphylococcal SAgs; (2) diversity of gene locations and molecular structural characteristics; (3) biological characteristics and activities; (4) multi-pathogenicity of SAgs in animal and human diseases, including bovine mastitis, swine sepsis, abscesses and skin edema in pig, arthritis and septicemia in poultry, and nosocomial infections and food-borne diseases in humans.

Impact of Superantigen-Producing Bacteria on T Cells from Tonsillar Hyperplasia

Staphylococcus aureus and Group A Streptococcus (GAS) are common occupants of the tonsils and many strains produce potent exotoxins (mitogens) that directly target T cells, which could be a driver for tonsillar hyperplasia. Tonsil tissues from 41 patients were tested for these bacteria in conjunction with profiling of B and T cells by flow cytometry. S. aureus and GAS were detected in tonsil tissue from 44% and 7%, respectively, of patients by bacteriological culture; immuno-histology showed bacteria in close proximity to both B and T lymphocytes. The presence of tonsillar S. aureus did not alter B or T cell populations, whereas peripheral blood mucosal-associated invariant T (MAIT) cells were significantly increased in S. aureus culture positive individuals (p < 0.006). Alterations of tonsil CD4⁺ TCR Vβ family members relative to peripheral blood were evident in 29 patients. Three patients had strong TCR Vβ skewing indicative of recent exposure to superantigens, their tonsils contained mitogenic bacteria, and supernatants from these bacteria were used to partially recapitulate the skewing profile in vitro, supporting the notion that superantigens can target tonsillar T cells in situ. Tonsils are a reservoir for superantigen-producing bacteria with the capacity to alter the composition and function of key immune cells.

Causes of Kawasaki Disease-From Past to Present

Kawasaki disease (KD) is a multisystem vasculitis that primarily affects the coronary arteries of young children. The causes of KD remain a mystery. It is suspected that some sort of infectious agent is involved because KD has epidemicity and seasonality. That said, the incidence of the disease is high among Japanese people, so it can be speculated that the hosts may have some sort of genetic characteristic that leaves them susceptible to KD. Various theories regarding the etiology have been asserted, such as the infectious vasculitis theory, autoantigen theory, superantigen theory, and RNA virus theory; however, none of them have been able to overcome this epidemicity. Taking into consideration the knowledge gained from previous reports, the best scenario explaining the pathogenesis is "individuals with certain genetic backgrounds are affected by microorganisms which trigger KD." In this article, the pathogenesis of KD is discussed with a focus on the microorganisms mentioned above, along with the previous and current hypotheses as well as my own opinion.

Staphylococcus aureus Lipoprotein Induces Skin Inflammation, Accompanied with IFN-γ-Producing T Cell Accumulation through Dermal Dendritic Cells

Staphylococcus aureus (S. aureus) is a commensal bacteria on the human skin, which causes serious skin inflammation. Several immune cells, especially effector T cells (Teff), have been identified as key players in S. aureus-derived skin inflammation. However, the bacterial component that induces dramatic host immune responses on the skin has not been well characterized. Here, we report that S. aureus lipoprotein (SA-LP) was recognized by the host immune system as a strong antigen, so this response induced severe skin inflammation. SA-LP activated dendritic cells (DCs), and this activation led to Teff accumulation on the inflamed skin in the murine intradermal (ID) injection model. The skin-accumulated Teff pool was established by IFN-ɤ-producing CD4⁺ and CD8⁺T (Th1 and Tc1). SA-LP activated dermal DC (DDC) in a dominant manner, so that these DCs were presumed to possess the strong responsibility of SA-LP-specific Teff generation in the skin-draining lymph nodes (dLN). SA-LP activated DC transfer into the mice ear, which showed similar inflammation, accompanied with Th1 and Tc1 accumulation on the skin. Thus, we revealed that SA-LP has a strong potential ability to establish skin inflammation through the DC-Teff axis. This finding provides novel insights not only for therapy, but also for the prevention of S. aureus-derived skin inflammation.

Origin, function and role in the development of skin diseases CLA+T-lymphocytes

The idea of CLA+T-lymphocytes, which are a special subpopulation of cells with a tropic to the skin, is given. The issues of maturation, migration and functional features of CLA+T-cells are considered. Special attention is paid to the different phenotype of memory T-cells. Modern data concerning the role of CLA+T-cells in the pathogenesis of autoimmune and allergic dermatoses, as well as malignant skin tumors are also presented. The conclusion about the necessity of further study of CLA +T-lymphocytes for detailed understanding of pathogenesis and search of variants of targeted therapy in psoriasis, atopic dermatitis, skin lymphomas and other skin diseases is made.

Biologics for the primary care physician: Review and treatment of psoriasis

Psoriasis is a chronic inflammatory disease that affects approximately 7.5 million people in the United States. The disease results in significant suffering, morbidity, and economic impact. Psoriasis is a multifaceted disease with a strong genetic component. Genetic data has revealed the presence of particular risk alleles in patients with psoriasis. Triggers of the disease have been elucidated and include factors such as trauma, obesity, infection, stress, and medications. At its core, psoriasis is a result of a dysfunctional immune response with T-cells at the center of immunogenesis. Clinically, psoriasis is characterized by discrete, erythematous scaly plaques. These lesions are often found on extensor surfaces, especially the elbows and knees. Although extensor surfaces are the prototypical destination of lesions, psoriasis may affect any area of the skin including the scalp, intertriginous areas, nails, palms, and soles. Location of lesions are important in assessing the impact on quality of life for patients. Diagnosis of psoriasis can typically be made clinically based on characteristic history and physical examination findings. In rare cases, biopsy may be needed to rule out other papulosquamous disease. Histologic findings of psoriasis can be non-specific and include marked epidermal hyperplasia, dilated vessels within the dermal papilla, and elongated rete ridges. Importantly, psoriasis is a systemic disease and organ systems outside of the skin must be considered. Co-morbidities of psoriasis include psoriatic arthritis, type 2 diabetes mellitus, cardiovascular disease, psychiatric disease, inflammatory bowel disease, neoplasms, and ocular disease. Management of psoriasis depends on the severity of the disease. In mild to moderate cases, topical medications are the cornerstone of treatment. Topical corticosteroids are the most commonly used and have limited systemic effects due to the localized application of medication. In moderate to severe cases of psoriasis, topical medications are ineffective and not feasible. Phototherapy and non-biologic systemic medications have been useful treatments; however, phototherapy is time consuming and non-biologic systemics have only modest response rates. In the last decade, biologic medications have become an important component of care for treating moderate to severe psoriasis. These medications target various cytokines responsible for psoriasis manifestations such as tumor necrosis factor (TNF-α), interleukin-12, interleukin-23, and interleukin-17. In the past 15 years, numerous biologic medications have been granted FDA approval, with the majority approved in the past several years. Some of the commonly used biologics include etanercept, adalimumab, infliximab, ixekizumab, secukinumab, brodalumab, guselkumab, ustekinumab, and tildrakizumab. Given the wealth of new biologics, current treatment guidelines have rapidly become outdated. This review provides summarized information of landmark trials that led to the approval of these medications.

Human T cell immune surveillance: Phenotypic, functional and migratory heterogeneity for tailored immune responses

The human immune system constantly provides a balance between pathogen clearance as well as tolerance for autoantigens and the commensal microbiota. This is achieved by immune responses, which are highly specialized and diversified in terms of their phenotype, function, regulation and location. Despite the complexity that is inherent to human immunity, our current knowledge is primarily shaped by very reductionist insights gained from peripheral blood T cells. Since only 2% of human T cells recirculate in the blood, the vast majority remains undetected by common sampling strategies and therefore unexplored. This review highlights and discusses recent developments in human T cell immune surveillance with a particular focus on functional and migratory T cell heterogeneity and provides a critical framework for new conceptual ideas, which could serve as a starting point in the quest for novel targeted therapies for chronic tissue restricted inflammatory diseases.

Circulating CLA+ T cells in atopic dermatitis and their possible role as peripheral biomarkers

Cutaneous lymphocyte-associated antigen (CLA⁺ ) T cells are specialized for skin homing and represent the main T-cell population in atopic dermatitis (AD) lesions. CLA⁺ is expressed on the surface of circulating CD45RO⁺ memory T cells and most skin-infiltrating T cells. Mechanistic studies and thus treatment advancements are limited by the need of large number of skin biopsies. Circulating CLA⁺ T cells may be a reliable surrogate marker of the inflammatory events occurring in the skin, and thus, the evaluation of CLA⁺ T cells in the blood may eliminate the need for skin biopsies. Preliminary work in AD has established that disease-associated T-cell abnormalities can be approached by either a study of skin lesions or activated CLA⁺ T-cell subsets in peripheral blood. Future studies in adults and children, across different skin disorders, correlating blood and skin phenotypes and determining skin-homing T-cell functional properties are needed to establish whether CLA⁺ memory subsets can be used as biomarkers and a substitute for skin biopsies. This review summarizes the latest advancements reached on circulating CLA⁺ in AD and the great potential they harbor in understanding AD mechanisms.

Streptococcus pyogenes-induced cutaneous lymphocyte antigen-positive T cell-dependent epidermal cell activation triggers TH17 responses in patients with guttate psoriasis

BACKGROUND

Guttate psoriasis (GP) is characterized by acute onset of small, rounded psoriatic lesions. Although this particular phenotype of psoriasis is usually associated with streptococcal throat infections and mainly occurs in HLA-Cw6(+) patients, the specific immunologic response to this innate stimulus that causes these skin lesions is poorly understood.

OBJECTIVE

This study aims to elucidate how key cellular elements of patients with GP respond to Streptococcus pyogenes and whether this initial immune response is favored by the genetic and environmental background of these patients.

METHODS

Circulating memory T cells and autologous epidermal cells from samples from either patients with GP (n = 14) or healthy control subjects (n = 6) were cocultured ex vivo in the presence of an S pyogenes extract. Levels of the psoriasis-associated cytokines IL-17A, IL-17F, IFN-γ, TNF-α, IL-6, and IL-8 were determined. The expression of several genes with increased (DEFB4, S100A7, LCN2, IL36G, IL8, CXCL9, CXCL10, and CXCL11) or decreased (FLG and LOR) transcripts in psoriatic lesions was examined in keratinocytes treated with coculture supernatants.

RESULTS

When skin-homing effector memory cutaneous lymphocyte antigen-positive T cells were used in cocultures, a TH17-dominant response was observed, as reflected by the higher amounts of IL-17A and IL-17F than IFN-γ. Moreover, a higher TH17 response was observed in cells isolated from patients with flares associated with a streptococcal tonsillitis and with the HLA-Cw6 allele (cohort 1). In addition, in normal keratinocytes the supernatants from these cocultures induced an increase in IL-17-associated genes, such as DEFB4, S100A7, LCN2, IL36G, and IL8 but a decrease in FLG and LOR, thereby confirming the role of activated TH17 cells.

CONCLUSION

This study reveals a dominant TH17 response of cutaneous lymphocyte antigen-positive T cells activated by epidermal cells and S pyogenes in patients with GP.

Far East Scarlet-Like Fever: A Review of the Epidemiology, Symptomatology, and Role of Superantigenic Toxin: Yersinia pseudotuberculosis-Derived Mitogen A

Far East scarlet-like fever (FESLF) is a severe inflammatory disease that occurs sporadically and in outbreaks in Russia and Japan. Far East scarlet-like fever is caused by Yersinia pseudotubuclosis infection, an organism that typically causes self-limiting gastroenteritis in Europe. Studies suggest the ability of Far Eastern strains to produce superantigen toxin Y pseudotuberculosis-derived mitogen A is integral to FESLF pathogenesis. In Europe, human Y pseudotuberculosis infection typically occurs sporadically, in the form of a self-limiting gastroenteritis. In Russia and Japan, outbreaks of Y pseudotuberculosis infection cause severe systemic inflammatory symptoms. This disease variant is called FESLF. Geographical heterogeneity exists between virulence factors produced by European and Far Eastern Y pseudotuberculosis strains, implicating superantigen Y pseudotuberculosis-derived mitogen A (YPMa) in the pathogenesis of FESLF. This article describes the epidemiology and clinical features of FESLF, and it presents the evidence for the role of YPMa in FESLF pathogenesis.

Ustekinumab in the Treatment of Psoriasis and Psoriatic Arthritis

Biologics have revolutionized the therapy of the psoriatic disease spectrum. These new classes of drugs also allow deeper insight into the pathogenesis of the disease and highlight the existence of distinct "molecular" disease subgroups as evidenced by the spectrum of clinical response seen. Molecules associated with both the interleukin (IL)-17 and interferon (IFN)γ pathways have important functions in psoriatic inflammation, and both are targeted by drugs acting on the p40 subunit shared by IL-12 and IL-23. These IL-12 family members are upstream of pathways characterized by the production of IFNγ and IL-17 related molecules, including IL-17, IL-22, and CCL20. We here summarize the mode of action and clinical studies of the p40 inhibitor ustekinumab with focus on both psoriasis and psoriatic arthritis.

Attenuation of peripheral regulatory T-cell suppression of skin-homing CD8⁺T cells in atopic dermatitis

PURPOSE

Cutaneous lymphocyte-associated antigen (CLA)-expressing CD8⁺T cells have been known to play an important role in the pathogenesis of atopic dermatitis (AD). However, the mechanisms underlying the loss of self-tolerance remain unclear. Regulatory T cells (Tregs) play a key role in the development of homeostasis in the immune system. We, therefore, hypothesized that a reduced ability of Tregs to inhibit autologous CD8⁺CLA⁺T cells might be underlying mechanism in AD.

MATERIALS AND METHODS

CD8⁺CLA⁺T cells and Tregs were obtained from the peripheral blood of AD patients and control volunteers. The frequencies of CD8⁺CLA⁺T cells were evaluated. The proliferative responses of CD8⁺CLA⁺T cells were assessed by flow cytometry, and the levels of transforming growth factor-β1 (TGF-β1) and interleukin-10 (IL-10) in culture supernatants were detected by enzyme-linked immunosorbent assay.

RESULTS

Our results revealed higher frequency and increased expression of perforin and granzyme-B in peripheral CD8⁺CLA⁺T cells in AD, and lower inhibitory ability of Tregs on proliferation of CD8⁺CLA⁺T cells in AD. Meanwhile, the levels of TGF-β1 produced by Tregs were significantly lower in AD, and anti-TGF-β1 abolished such suppression.

CONCLUSION

The attenuated inhibitory ability of Tregs on hyper-activated autologous CD8⁺CLA⁺T cells, mediated by TGF-β1, plays an important role in the pathogenesis of AD.

The IL-17A-producing CD8+ T-cell population in psoriatic lesional skin comprises mucosa-associated invariant T cells and conventional T cells

IL-17A is pivotal in the etiology of psoriasis, and CD8(+) T cells with the ability to produce this cytokine (Tc17 cells) are over-represented in psoriatic lesions. Here we demonstrate that the frequency of Tc17 cells in peripheral blood of psoriasis patients correlated with the clinical severity of the disease. Analysis of cutaneous-associated lymphocyte antigen expression showed that the blood Tc17 population contains a significantly higher proportion of cells with skin-homing potential compared with the CD8(+) T-cell population lacking IL-17A/IL-22 expression. IL-17A-producing CD8(+) T cells in blood have previously been reported to belong mainly to the mucosa-associated invariant T-cell (MAIT cell) lineage characterized by TCR Vα7.2 chain, CD161, IL-18Rα, and multidrug transporter ABCB1 expression. We demonstrate the presence of CD8(+) MAIT cells in the dermis and epidermis of psoriatic plaques, as well as healthy skin; however, IL-17A-producing CD8(+) MAIT cells were predominantly found in psoriatic skin. Notably, we observed IL-17A production in a large proportion of psoriatic plaque-derived CD8(+) T cells devoid of MAIT cell characteristics, likely representing conventional CD8(+) T cells. In conclusion, we provide supporting evidence that implicates Tc17 cells in the pathogenesis of psoriasis and describe the presence of innate CD8(+) MAIT cells in psoriatic lesions as an alternative source of IL-17A.

Effect of tonsillectomy on psoriasis: a systematic review

BACKGROUND

Streptococcal infection is associated with psoriasis onset in some patients. Whether tonsillectomy decreases psoriasis symptoms requires a systematic review of the literature.

OBJECTIVE

We sought to determine whether tonsillectomy reduces psoriasis severity through a comprehensive search of over 50 years of literature.

METHODS

We searched MEDLINE, CINAHL, Cochrane, EMBASE, Web of Science, and OVID databases (from August 1, 1960, to September 12, 2013) and performed a manual search of selected references. We identified observational studies and clinical trials examining psoriasis after tonsillectomy.

RESULTS

We included data from 20 articles from the last 53 years with 545 patients with psoriasis who were evaluated for or underwent tonsillectomy. Of 410 reported cases of patients with psoriasis who underwent tonsillectomy, 290 experienced improvement in their psoriasis. Although some patients who underwent tonsillectomy experienced sustained improvement in psoriasis, others experienced psoriasis relapse after the procedure.

LIMITATIONS

Fifteen of 20 publications were case reports or series that lacked control groups. Publication bias favoring reporting improved cases needs to be considered.

CONCLUSION

Tonsillectomy may be a potential option for patients with recalcitrant psoriasis associated with episodes of tonsillitis. Studies with long-term follow-up are warranted to determine more clearly the extent and persistence of benefit of tonsillectomy in psoriasis.

A Case of Severe HIV-Associated Psoriasis Successfully Treated with Acitretin Therapy

Psoriasis is a chronic inflammatory skin disease that involves immune-mediated cutaneous inflammation and keratinocyte hyperproliferation. Psoriasis in patients with HIV responds poorly to treatment and has a high morbidity rate, thus posing a challenge to clinicians. Until now, there have been no documented cases of acitretin therapy for HIV-associated psoriasis in Korea. Here, we report a case of safe and successful therapy with acitretin in a 52-year-old man with HIV-associated psoriasis that responded poorly to previous treatments including steroids and ultraviolet B phototherapy. We also review the relevant literature.

Superantigens subvert the neutrophil response to promote abscess formation and enhance Staphylococcus aureus survival in vivo

Staphylococcus aureus is a versatile bacterial pathogen that produces T cell-activating toxins known as superantigens (SAgs). Although excessive immune activation by SAgs can induce a dysregulated cytokine storm as a component of what is known as toxic shock syndrome (TSS), the contribution of SAgs to the staphylococcal infection process is not well defined. Here, we evaluated the role of the bacterial superantigen staphylococcal enterotoxin A (SEA) in a bacteremia model using humanized transgenic mice expressing SAg-responsive HLA-DR4 molecules. Infection with S. aureus Newman induced SEA-dependent Vβ skewing of T cells and enhanced bacterial survival in the liver compared with infection by sea knockout strain. SEA-induced gamma interferon, interleukin-12, and chemokine responses resulted in increased infiltration of CD11b(+) Ly6G(+) neutrophils into the liver, promoting the formation of abscesses that contained large numbers of viable staphylococci. Hepatic abscesses occurred significantly more frequently in S. aureus Newman-infected livers than in livers infected with the Newman sea knockout strain, promoting the survival of S. aureus in vivo. This represents a novel mechanism during infection whereby S. aureus utilizes SAgs to form a specialized niche and manipulate the immune system.

Staphylococcal and streptococcal superantigen exotoxins

SUMMARY This review begins with a discussion of the large family of Staphylococcus aureus and beta-hemolytic streptococcal pyrogenic toxin T lymphocyte superantigens from structural and immunobiological perspectives. With this as background, the review then discusses the major known and possible human disease associations with superantigens, including associations with toxic shock syndromes, atopic dermatitis, pneumonia, infective endocarditis, and autoimmune sequelae to streptococcal illnesses. Finally, the review addresses current and possible novel strategies to prevent superantigen production and passive and active immunization strategies.

The association of sore throat and psoriasis might be explained by histologically distinctive tonsils and increased expression of skin-homing molecules by tonsil T cells

Recent studies have highlighted the involvement of the palatine tonsils in the pathogenesis of psoriasis, particularly among patients with recurrent throat infections. However, the underlying immunological mechanism is not well understood. In this study we confirm that psoriasis tonsils are infected more frequently by β-haemolytic Streptococci, in particular Group C Streptococcus, compared with recurrently infected tonsils from patients without skin disease. Moreover, we show that tonsils from psoriasis patients contained smaller lymphoid follicles that occupied a smaller tissue area, had a lower germinal centre to marginal zone area ratio and contained fewer tingible body macrophages per unit area compared with recurrently infected tonsils from individuals without skin disease. Psoriasis patients' tonsils had a higher frequency of skin-homing [cutaneous lymphocyte-associated antigen (CLA(+) )] CD4(+) and CD8(+) T cells, and this correlated significantly with their frequency of blood CLA(+) T cells. The psoriasis patients also had a higher frequency of tonsil T cells expressing the interleukin (IL)-23 receptor that was expressed preferentially by the CLA(+) T cell population. In contrast, recurrently infected tonsils of individuals without skin disease had a higher frequency of tonsil T cells expressing the activation marker CD69 and a number of chemokine receptors with unknown relevance to psoriasis. These findings suggest that immune responses in the palatine tonsils of psoriasis patients are dysregulated. The elevated expression of CLA and IL-23 receptor by tonsil T cells may promote the egression of effector T cells from tonsils to the epidermis, suggesting that there may be functional changes within the tonsils, which promote triggering or exacerbation of psoriasis.

Investigation of the cutaneous response to recall antigen in humans in vivo

In this paper we provide a detailed description of an experimental method for investigating the induction and resolution of recall immune response to antigen in humans in vivo. This involves the injection of tuberculin purified protein derivative (PPD) into the skin, followed by inducing suction blisters at the site of injection, from which leucocytes and cytokines that are involved in the response can be isolated and characterized. Using this technique we found that although the majority of CD4(+) T cells in the skin that are present early in the response express cutaneous lymphocyte antigen (CLA), the expression of this marker is reduced significantly in later phases. This may enable these cells to leave the skin during immune resolution. Furthermore, interleukin (IL)-2 production can be detected both in CD4(+) T cells and also in the blister fluid at the peak of the response at day 7, indicating that mediators found in the blister fluid are representative of the cytokine microenvironment in vivo. Finally, we found that older humans have defective ability to respond to cutaneous PPD challenge, but this does not reflect a global immune deficit as they have similar numbers of circulating functional PPD-specific CD4(+) T cells as young subjects. The use of the blister technology enables further characterization of the skin specific defect in older humans and also general mechanisms that govern immune regulation in vivo.

Pathological mechanisms of skin homing T cells in atopic dermatitis

Skin infiltration of circulating memory T cells with cutaneous tropism is considered one of the pathologic mechanisms in atopic dermatitis (AD). Skin-seeking circulating T lymphocytes can be identified by their expression of the cutaneous lymphocyte-associated antigen on the cell surface. Recent studies have contributed useful new information about the function and recirculation properties of those cells in AD patients. This review integrates the latest findings on peripheral cutaneous lymphocyte-associated antigen memory T cells in AD and highlights the relevance of this cell type and its importance to our understanding of the pathologic mechanisms of AD.

The role of the palatine tonsils in the pathogenesis and treatment of psoriasis

Psoriasis is a common chronic skin disease with strong genetic associations and environmental triggers. Patients with psoriasis develop sore throats much more frequently than nonpsoriatic individuals and it is well documented that streptococcal throat infections can trigger the onset of psoriasis, and such infections cause exacerbation of chronic psoriasis. It is now generally accepted that psoriatic lesions are caused by abnormal reactivity of specific T lymphocytes in the skin. However, it has been shown in recent years that activation of specific immunity is always preceded by activation of nonspecific innate immune mechanisms, and that abnormalities in the innate immune system can cause dysregulation in specific immune responses. Here we explore the possible immune mechanisms that are involved in the link between infection of the tonsils and this inflammatory skin disease. Moreover, we survey the literature and discuss the suitability of tonsillectomy as a treatment for psoriasis.

Xenogeneic graft-versus-host-disease in NOD-scid IL-2Rγnull mice display a T-effector memory phenotype

The occurrence of Graft-versus-Host Disease (GvHD) is a prevalent and potentially lethal complication that develops following hematopoietic stem cell transplantation. Humanized mouse models of xenogeneic-GvHD based upon immunodeficient strains injected with human peripheral blood mononuclear cells (PBMC; “Hu-PBMC mice”) are important tools to study human immune function in vivo. The recent introduction of targeted deletions at the interleukin-2 common gamma chain (IL-2Rγ^null), notably the NOD-scid IL-2Rγ^null (NSG) and BALB/c-Rag2^null IL-2Rγ^null (BRG) mice, has led to improved human cell engraftment. Despite their widespread use, a comprehensive characterisation of engraftment and GvHD development in the Hu-PBMC NSG and BRG models has never been performed in parallel. We compared engrafted human lymphocyte populations in the peripheral blood, spleens, lymph nodes and bone marrow of these mice. Kinetics of engraftment differed between the two strains, in particular a significantly faster expansion of the human CD45⁺ compartment and higher engraftment levels of CD3⁺ T-cells were observed in NSG mice, which may explain the faster rate of GvHD development in this model. The pathogenesis of human GvHD involves anti-host effector cell reactivity and cutaneous tissue infiltration. Despite this, the presence of T-cell subsets and tissue homing markers has only recently been characterised in the peripheral blood of patients and has never been properly defined in Hu-PBMC models of GvHD. Engrafted human cells in NSG mice shows a prevalence of tissue homing cells with a T-effector memory (T_EM) phenotype and high levels of cutaneous lymphocyte antigen (CLA) expression. Characterization of Hu-PBMC mice provides a strong preclinical platform for the application of novel immunotherapies targeting T_EM-cell driven GvHD.

New insights of T cells in the pathogenesis of psoriasis

Psoriasis is one of the most common immune-mediated chronic, inflammatory skin diseases characterized by hyperproliferative keratinocytes and infiltration of T cells, dendritic cells, macrophages and neutrophils. Although the pathogenesis of psoriasis is not fully understood, there is ample evidence suggesting that the dysregulation of immune cells in the skin, particularly T cells, plays a critical role in psoriasis development. In this review, we mainly focus on the pathogenic T cells and discuss how these T cells are activated and involved in the disease pathogenesis. Newly identified 'professional' IL-17-producing dermal γδ T cells and their potential role in psoriasis will also be included. Finally, we will briefly summarize the recent progress on the T cell and its related cytokine-targeted therapy for psoriasis treatment.

Staphylococcal superantigens in colonization and disease

Superantigens (SAgs) are a family of potent immunostimulatory exotoxins known to be produced by only a few bacterial pathogens, including Staphylococcus aureus. More than 20 distinct SAgs have been characterized from different S. aureus strains and at least 80% of clinical strains harbor at least one SAg gene, although most strains encode many. SAgs have been classically associated with food poisoning and toxic shock syndrome (TSS), for which these toxins are the causative agent. TSS is a potentially fatal disease whereby SAg-mediated activation of T cells results in overproduction of cytokines and results in systemic inflammation and shock. Numerous studies have also shown a possible role for SAgs in other diseases such as Kawasaki disease (KD), atopic dermatitis (AD), and chronic rhinosinusitis (CRS). There is also now a rich understanding of the mechanisms of action of SAgs, as well as their structures and function. However, we have yet to discover what purpose SAgs play in the life cycle of S. aureus, and why such a wide array of these toxins exists. This review will focus on recent developments within the SAg field in terms of the molecular biology of these toxins and their role in both colonization and disease.

Induction of contact-dependent CD8(+) regulatory T cells through stimulation with staphylococcal and streptococcal superantigens

The bacterial superantigen exotoxins of Staphylococcus aureus and Streptococcus pyogenes are potent stimulators of polyclonal T-cell proliferation. They are the causes of toxic shock syndrome but also induce CD25(+)  FOXP3(+) regulatory cells in the CD4 compartment. Several studies have recently described different forms of antigen-induced regulatory CD8(+) T cells in the context of inflammatory diseases and chronic viral infections. In this paper we show that bacterial superantigens are potent inducers of human regulatory CD8(+) T cells. We used four prototypic superantigens of S. aureus (toxic shock syndrome toxin-1 and staphylococcal enterotoxin A) and Str. pyogenes (streptococcal pyrogenic exotoxins A and K/L). At concentrations below 1 ng/ml each toxin triggers concentration-dependent T-cell receptor Vβ-specific expression of CD25 and FOXP3 on CD8(+) T cells. This effect is independent of CD4(+) T-cell help but requires antigen-presenting cells for maximum effect. The cells also express the activation/regulatory markers cytotoxic T-lymphocyte antigen-4 and glucocorticoid-induced tumour necrosis factor receptor-related protein and skin homing adhesins CD103 and cutaneous lymphocyte-associated antigen. Superantigen-induced CD25(+)  FOXP3(+)  CD8(+) T cells were as potent as freshly prepared naturally occurring CD4(+) regulatory T cells in suppressing proliferation of CD4(+)  CD25(-) T cells in response to anti-CD3 stimulation. Although superantigen-induced CD8(+)  CD25(+) FOXP3(+) express interleukin-10 and interferon-γ their suppressive function is cell contact dependent. Our findings indicate that regulatory CD8(+) T cells may be a feature of acute bacterial infections contributing to immune evasion by the microbe and disease pathogenesis. The presence and magnitude of regulatory CD8(+) T-cell responses may represent a novel biomarker in such infections. Superantigen-induced regulatory CD8(+) T cells also have therapeutic potential.

Identification of a novel proinflammatory human skin-homing Vγ9Vδ2 T cell subset with a potential role in psoriasis

γδ T cells mediate rapid tissue responses in murine skin and participate in cutaneous immune regulation including protection against cancer. The role of human γδ cells in cutaneous homeostasis and pathology is characterized poorly. In this study, we show in vivo evidence that human blood contains a distinct subset of proinflammatory cutaneous lymphocyte Ag and CCR6-positive Vγ9Vδ2 T cells, which is rapidly recruited into perturbed human skin. Vγ9Vδ2 T cells produced an array of proinflammatory mediators including IL-17A and activated keratinocytes in a TNF-α- and IFN-γ-dependent manner. Examination of the common inflammatory skin disease psoriasis revealed a striking reduction of circulating Vγ9Vδ2 T cells in psoriasis patients compared with healthy controls and atopic dermatitis patients. Decreased numbers of circulating Vγ9Vδ2 T cells normalized after successful treatment with psoriasis-targeted therapy. Taken together with the increased presence of Vγ9Vδ2 T cells in psoriatic skin, these data indicate redistribution of Vγ9Vδ2 T cells from the blood to the skin compartment in psoriasis. In summary, we report a novel human proinflammatory γδ T cell involved in skin immune surveillance with immediate response characteristics and with potential clinical relevance in inflammatory skin disease.

The cellular orchestra in skin allergy; are differences to lung and nose relevant?

PURPOSE OF REVIEW

It has been a long lasting question that although a similar peripheral allergen-specific immune response has been observed, why some patients show only atopic dermatitis, rhinitis and asthma alone or their combinations. The answer resides in the propensity of resident tissue cells and local antigen-presenting cells and T cells for developing an allergic inflammatory immune response. Antigen-presenting cells introduce processed allergens to T helper lymphocytes, where a decision of developing different types of T cell immunity is given under the influence of several cytokines, chemokines, costimulatory signals and regulatory T cells.

RECENT FINDINGS

We focused in this review article on effector T cell subsets, which have been recently described such as Th9, Th17 cells and Th22 cells, which are characterized by their IL-9 and IL-10, IL-17 (or IL-17A) and IL-22 expression, respectively together with other proinflammatory cytokines, which coordinate local tissue inflammation. Both naturally occurring CD4+CD25+ regulatory T (Treg) cells and inducible populations of allergen-specific, IL-10-secreting Treg type 1 cells inhibit allergen-specific effector cells and have been shown to play a central role in the maintenance of peripheral homeostasis and the establishment of controlled immune responses in allergic inflammatory tissues.

SUMMARY

Better understanding and characterization of newly described effector cell subsets and their interaction between antigen presenting cells and resident tissue cells will enlighten our knowledge on the mechanisms of allergic diseases.

Staphylococcal alpha-toxin is a strong inducer of interleukin-17 in humans

Patients with atopic dermatitis (AD) are frequently colonized with Staphylococcus aureus, with one-third of isolates producing alpha-toxin. Moreover, S. aureus colonization is positively correlated with the severity of eczema. Interleukin-17A (IL-17A) has gained attention in diseases associated with chronic skin infections. The aim of this study was to investigate the effects of sublytic alpha-toxin concentrations on IL-17A production. Sublytic alpha-toxin concentrations strongly induced IL-17A in peripheral blood mononuclear cells (PBMCs), isolated CD4(+) T cells, polarized Th17 cells, and Th17 clones from reactive atopy patch test lesions and blood from AD patients. Alpha-toxin induced IL-17A directly in T cells. The effect of alpha-toxin was further amplified by upregulation of IL-1 in monocytes. In conclusion, higher levels of IL-17A secretion induced by alpha-toxin in the skin partially explain how colonization with S. aureus can contribute to chronic skin inflammation.

The role of 9-O-acetylated ganglioside D3 (CD60) and {alpha}4{beta}1 (CD49d) expression in predicting the survival of patients with Sezary syndrome

BACKGROUND

Sézary syndrome is a rare and very aggressive leukemic variant of cutaneous T-cell lymphoma characterized by extensive skin involvement and a malignant circulating CD4(+) T-cell clone which homes to the skin, over-expresses CD60, and lacks CD7, CD26 and CD49d. So far prognostic markers in this disease are limited to treatment with systemic steroids, age, serum lactate dehydrogenase, and a white blood cell count of 20×10(9)/L or higher: no other biological marker with prognostic value, especially related to malignant cells, has been described.

DESIGN AND METHODS

We used flow activated cell sorting analysis to compare the distribution of the T-cell receptor-Vβ repertoire and several surface molecules (CD7, CD26, CD49d and CD60) within the circulating CD4(+) T-cell population in 62 patients with Sézary syndrome, 180 with mycosis fungoides, 6 with B-cell lymphomas, and 19 with chronic eczema. We calculated the 5-year overall survival of patients with Sézary syndrome after first hospital admission using Kaplan-Meier product-limit estimates and hazard ratios from the Cox proportional hazards model.

RESULTS

We found that both higher number of CD60(+) and lower number of CD49d(+) cells within circulating CD4(+) T cells at disease presentation were significantly associated with a lower probability of survival. An exceedingly high risk of death was observed for patients with a combination of a high proportion of CD4(+)CD60(+) cells (≥ 0.5×10(9)/L) and low proportion of CD4(+)CD49d(+) cells (<0.5×10(9)/L) (hazard ratio = 12.303, 95% confidence interval 1.5-95.9; P<0.02). In addition, a skewed usage of T-cell receptor-Vβ subfamilies was observed in the circulating T-cell clone for 61.9% of all patients with Sézary syndrome, T-cell receptor-Vβ 2 and 5.1 subfamilies being the most frequently represented (42.8%), followed by T-cell receptor-Vβ 12 and 13.1.

CONCLUSIONS

In this study we showed that up-regulation of CD60 and down-regulation of CD49d on circulating CD4(+) T cells are two useful markers for predicting a very poor outcome in patients with Sézary syndrome.

Heat shock proteins and superantigenic properties of bacteria from the gastrointestinal tract of patients with Kawasaki disease

We previously suggested that gut bacteria may be involved in the onset of Kawasaki disease (KD). In this study, we evaluated the production of heat shock proteins (hsps) and superantigens (sAgs) by microorganisms isolated from the jejunal mucosa of 19 children with KD in the acute phase and from 15 age-matched control children. We identified 13 strains of Gram-negative microbes from patients with KD; these microbes produced large amounts of hsp60 and induced pro-inflammatory cytokine production by peripheral blood mononuclear cells. The Gram-negative microbes also elicited endogenous hsp60 production, leading to the secretion of anti-inflammatory intereukin-10 (IL-10). We also identified 18 strains of Gram-positive cocci that had superantigenic properties and which induced the expansion of Vβ2 T cells in vitro. All bacteria identified in this study were antibiotic resistant. These data suggest that sAg and hsps produced by gut bacteria might be involved in KD.

Glycosyltransferase-programmed stereosubstitution (GPS) to create HCELL: engineering a roadmap for cell migration

During evolution of the vertebrate cardiovascular system, the vast endothelial surface area associated with branching vascular networks mandated the development of molecular processes to efficiently and specifically recruit circulating sentinel host defense cells and tissue repair cells at localized sites of inflammation/tissue injury. The forces engendered by high-velocity blood flow commensurately required the evolution of specialized cell surface molecules capable of mediating shear-resistant endothelial adhesive interactions, thus literally capturing relevant cells from the blood stream onto the target endothelial surface and permitting subsequent extravasation. The principal effectors of these shear-resistant binding interactions comprise a family of C-type lectins known as 'selectins' that bind discrete sialofucosylated glycans on their respective ligands. This review explains the 'intelligent design' of requisite reagents to convert native CD44 into the sialofucosylated glycoform known as hematopoietic cell E-/L-selectin ligand (HCELL), the most potent E-selectin counter-receptor expressed on human cells, and will describe how ex vivo glycan engineering of HCELL expression may open the 'avenues' for the efficient vascular delivery of cells for a variety of cell therapies.

PSGL-1 function in immunity and steady state homeostasis

The substantial importance of P-selectin glycoprotein ligand 1 (PSGL-1) in leukocyte trafficking has continued to emerge beyond its initial identification as a selectin ligand. PSGL-1 seemed to be a relatively simple molecule with an extracellular mucin domain extended as a flexible rod, teleologically consistent with its primary role in tethering leukocytes to endothelial selectins. The rolling interaction between leukocyte and endothelium mediated by this selectin-PSGL-1 interaction requires branched O-glycan extensions on specific PSGL-1 amino acid residues. In some cells, such as neutrophils, the glycosyltransferases involved in formation of the O-glycans are constitutively expressed, while in other cells, such as T cells, they are expressed only after appropriate activation. Thus, PSGL-1 supports leukocyte recruitment in both innate and adaptive arms of the immune response. A complex array of amino acids within the selectins engage multiple sugar residues of the branched O-glycans on PSGL-1 and provide the molecular interactions responsible for the velcro-like catch bonds that support leukocyte rolling. Such binding of PSGL-1 can also induce signaling events that influence cell phenotype and function. Scrutiny of PSGL-1 has revealed a better understanding of how it performs as a selectin ligand and yielded unexpected insights that extend its scope from supporting leukocyte rolling in inflammatory settings to homeostasis including stem cell homing to the thymus and mature T-cell homing to secondary lymphoid organs. PSGL-1 has been found to bind homeostatic chemokines CCL19 and CCL21 and to support the chemotactic response to these chemokines. Surprisingly, the O-glycan modifications of PSGL-1 that support rolling mediated by selectins in inflammatory conditions interfere with PSGL-1 binding to homeostatic chemokines and thereby limit responsiveness to the chemotactic cues used in steady state T-cell traffic. The multi-level influence of PSGL-1 on cell traffic in both inflammatory and steady state settings is therefore substantially determined by the orchestrated addition of O-glycans. However, central as specific O-glycosylation is to PSGL-1 function, in vivo regulation of PSGL-1 glycosylation in T cells remains poorly understood. It is our purpose herein to review what is known, and not known, of PSGL-1 glycosylation and to update understanding of PSGL-1 functional scope.

Isolation of alpha-toxin-producing Staphylococcus aureus from the skin of highly sensitized adult patients with severe atopic dermatitis

BACKGROUND

Staphylococcus aureus (S. aureus) is a well-known trigger factor of atopic dermatitis (AD). Besides staphylococcal superantigens, alpha-toxin may influence cutaneous inflammation via induction of T-cell proliferation and cytokine secretion.

OBJECTIVES

To investigate the association between sensitization to inhalant allergens and skin colonization with alpha-toxin-producing S. aureus in AD.

PATIENTS AND METHODS

We investigated 127 patients with AD, aged 14-65 years, who were on standard anti-inflammatory and antiseptic treatment before investigation. We evaluated skin colonization, medical history, severity of AD and sensitization to inhalant allergens.

RESULTS

Forty-eight of 127 patients were colonized with S. aureus, suffered from more severe AD, had asthma more often and showed higher sensitization levels to inhalant allergens. Thirty of 48 patients with S. aureus skin-colonizing strains produced alpha-toxin and had higher total IgE and specific IgE to birch pollen and timothy grass pollen.

CONCLUSIONS

Under topical treatment with antiseptic and anti-inflammatory agents the colonization of lesional skin with S. aureus was clearly lower than commonly found in untreated patients with AD. Colonization with S. aureus was associated with a higher severity of AD, higher degree of sensitization, and a higher frequency of asthma. The proportion of patients whose skin was colonized with alpha-toxin-producing S. aureus was higher than expected from a former study. Cutaneous colonization with alpha-toxin-producing S. aureus was associated with a higher sensitization level to birch pollen allergen in AD. This may point to a higher susceptibility of patients with higher T-helper 2 polarization towards alpha-toxin-producing S. aureus.