Presence of IgE antibodies to staphylococcal exotoxins on the skin of patients with atopic dermatitis. Evidence for a new group of allergens

Allergic skin disease: atopic dermatitis as a prototype

The skin is the largest immune organ in the body. It is strategically positioned as an interface between a hostile antigenic world and a complex immune system characterized by inflammatory cells, mediators, lymphocytes, and a panoply of cytokines. These cytokines act as subcellar messengers that direct effector lymphocytes, eosinophils, mast cells, and a host of other cells to target the skin in allergic inflammation. Just as asthmas and allergic rhinitis are prototypes of IgE-mediated respiratory disease, atopic dermatitis is the prototype allergic skin disease. This article focuses on an understanding of the pathogenic mechanisms involved in atopic dermatitis and outlines the clinical spectrum of cutaneous allergic disease. Finally, a state-of-the-art approach to treatment is offered to the clinician confronted with the management of this difficult disorder.

The role of superantigens in human diseases: therapeutic implications for the treatment of skin diseases

Although it is well established that immune mechanisms contribute to the pathogenesis of chronic inflammatory skin diseases such as atopic dermatitis (AD) and psoriasis, the actual events that trigger the immunological pathways resulting in these skin diseases are not well understood. Colonization and infection with Staphylococcus aureus and streptococci has been reported to exacerbate AD and psoriasis. Recent studies demonstrating that bacterial toxins can act as superantigens provide mechanism(s) by which S. aureus and streptococci could mediate an inflammatory skin lesion that consists predominantly of activated T-cells and monocytes. This review will explore the diverse mechanisms by which bacterial superantigens can induce skin inflammation following systemic or local infection. These observations provide a new direction for the development of novel approaches for the treatment of skin inflammation.

Staphylococcus aureus colonization in atopic dermatitis and its therapeutic implications

Skin colonization with Staphylococcus aureus is a characteristic feature of atopic dermatitis with more than 90% of patients being colonized. Extracellular matrix proteins are important for the adherence of S. aureus to human keratinocytes. The bacterium interferes in the inflammatory process of atopic dermatitis in various ways, among which the ability to release superantigens in a high percentage of clinical isolates is of great importance. As the colonization correlates significantly with the severity of eczema, anti-staphylococcal treatment measurements are widely used. In cases of atopic dermatitis exacerbation with wide-spread weeping lesions, a systemic antibiotic treatment is warranted, with erythromycin no longer being recommended due to an increased resistance rate. In localized superinfected lesions the topical application of an antibiotic-glucocorticoid preparation may offer advantages to the mere steroid application. Based on efficacy and resistance data, fusidic acid is the antibiotic of choice. There is evidence that phototherapy in atopic dermatitis may be even more effective when combined with anti-staphylococcal measurements. In the future new therapeutical options may be available.

Effects of recombinant human soluble interleukin-4 receptor on interleukin-4/staphylococcal enterotoxin B-stimulated peripheral mononuclear cells from patients with atopic eczema

In atopic eczema both in local inflammatory reactions and in peripheral blood high interleukin (IL) 4: interferon-gamma (IFN-gamma) production ratios have been demonstrated, indicating predominance of TH2 cell subsets resulting in increased IL-4 production and high serum IgE. The in vitro immunomodulatory effects of recombinant human soluble IL-4 receptor (rsIL-4R) on IL-4-stimulated lymphocyte proliferation, IgE and IFN-gamma production were studied in peripheral blood mononuclear cells from 10 patients with atopic eczema and seven healthy donors. In addition to control cultures (without any stimulus) and cultures with simultaneous application of rsIL-4R and IL-4, time-kinetic experiments were performed. We further investigated the influence of rsIL-4R on IL-4 production in staphylococcal enterotoxin B (SEB) stimulated peripheral blood mononuclear cells. Early addition of rsIL-4R to IL-4-stimulated peripheral blood mononuclear cells resulted in an increase in IFN-gamma production and in suppression of IL-4 induced proliferation and IgE secretion. Unexpectedly, rsIL-4R in combination with SEB exhibited an IL-4 protective effect with a significant increase in detectable IL-4 in the culture supernatants. The present data support the assumption that rsIL-4R might be a promising new immunomodulatory substance in the treatment of atopic eczema.

Production of antibodies to staphylococcal superantigens in atopic dermatitis

Staphylococcal superantigens (SAG) are implicated in the inflammation of atopic dermatitis. As SAG mediated diseases may be modified by specific antibodies, the antibody response to SAG in atopic dermatitis was investigated. Immunoglobulin (Ig) G to staphylococcal enterotoxin A (SEA), staphylococcal enterotoxin B (SEB), and toxic shock syndrome toxin 1 (TSST-1) were measured by sandwich enzyme linked immunosorbent assay (ELISA) in 74 children with atopic dermatitis and 111 controls. Controls had detectable IgG to SEA, SEB, and TSST-1, which increased with age. Atopic dermatitis subjects had an increased response to SEB at 6 months to 2 years (76% v 42%) and 2 to 7 years (79% v 57%), and equivalent responses to SEA and TSST-1, compared to controls. It is suggested that increased responses to SEB relate to increased colonisation and hence exposure to superantigen producing staphylococcus in atopic dermatitis, and that inflammation of atopic dermatitis is not caused by an inability to make antibody to SAG.

Circulating CLA+ lymphocytes from children with atopic dermatitis contain an increased percentage of cells bearing staphylococcal-related T-cell receptor variable segments

BACKGROUND

Atopic dermatitis is an allergic T-cell mediated skin inflammation. Staphylococcus aureus colonization is very common in cutaneous atopic dermatitis lesions. The cutaneous lymphocyte-associated antigen (CLA) is a T cell skin homing receptor that defines T lymphocytes associated with the cutaneous immune response.

OBJECTIVE

To study whether CLA+ T cells from atopic dermatitis children present a selective expression for Staphylococcus aureus-related TCR Vbeta segments.

METHODS

Peripheral blood T cells were stained with HECA-452 (anti-CLA) and a panel of TCR Vbeta specific monoclonal antibodies and analysed by flow cytometry.

RESULTS

Atopic dermatitis patients have a higher percentage of circulating CLA+ CD3+ lymphocytes compared with healthy controls. Patients with active atopic dermatitis during the study expressed a higher percentage of cells positive for the TCR Vbeta2 and Vbeta5.1 segments in the CLA+ but not in the CLA- subset. These TCR Vbetas are recognized by staphylococcal superantigens. Moreover, there was an increased percentage of HLA-DR+ expression by CLA+ Vbeta5.1+ T cells in patients with active atopic dermatitis, but those patients whose eczema was inactive had very similar values to healthy controls regarding TCR Vbeta and HLA-DR phenotype in circulating CLA+ T lymphocytes.

CONCLUSION

Our data indicate that circulating skin-homing T cells of patients with active atopic dermatitis contain an increased percentage of cells bearing TCR Vbeta segments related with Staphylococcus aureus. Staphylococcus superantigens may therefore trigger expansion or at least circulation of appropriate CLA+ T cells.

T cell- and perforin-dependent depletion of B cells in vivo by staphylococcal enterotoxin A

Bacterial superantigens bind to major histocompatibility complex (MHC) class II and subsequently activate both CD4+ and CD8+ T lymphocytes expressing certain T-cell receptor (TCR)-Vbeta chains. In response to superantigen exposure these subsets proliferate, produce large amounts of proinflammatory cytokines and in addition CD8+ cytotoxic T lymphocytes (CTL) are induced. Previous studies in vitro have shown that these CTL effectively lyse MHC class II-expressing cells presenting the proper superantigen. However, it is unknown whether superantigens induce a similar response towards MHC class II+ antigen-presenting cells in vivo. In this study we demonstrate that administration of repeated injections of the superantigen staphylococcal enterotoxin A (SEA) to TCR-Vbeta3 transgenic mice results in a loss of MHC class II-expressing cells in the spleen. Analysis of different MHC class II+ subsets revealed a selective depletion of CD19+ B cells, while F4/80+ macrophages increased in number. Depletion of T cells with anti-CD4 or anti-CD8 monoclonal antibody indicated that CD8+ T cells were crucial for SEA-induced cytotoxicity in vivo. Repeated injections of SEA to perforin-deficient mice resulted in significantly less B-cell depletion compared with control mice. This suggests that superantigen-activated CD8+ T cells lyse MHC class II+ antigen-presenting cells in a perforin-dependent manner in vivo. It is suggested that this represents a novel bacterial immune escape mechanism, which may particularly impair local humoral immune responses.

Toxin-mediated streptococcal and staphylococcal disease

After several decades of seemingly decreasing virulence, streptococcal and staphylococcal infections have reemerged as a major source of morbidity and mortality. Within the past 2 decades, not only have well-established diseases such as rheumatic fever begun to reappear. but also many new entities, such as toxic shock syndrome, streptococcal toxic shock syndrome, recurrent toxin-mediated perineal erythema, and recalcitrant erythematous desquamating disorder have been described. Central to the renewed importance of these bacteria has been the production of circulating toxins, which often function as superantigens in causing the clinical manifestations, morbidity and mortality associated with these diseases.

Staphylococcal enterotoxin B inhibits the production of interleukin-4 in a human mast-cell line HMC-1

Staphylococcal enterotoxins belong to the recently characterized group of immunocytotropic bacterial superantigens that are potent mitogens for human T cells. Superantigens are presented, but without intracellular processing, to T cells by monocyte/macrophages, Langerhans' cells and keratinocytes via the class II major histocompatibility complex (MHC) molecules. Superantigens have been demonstrated to act as potent inducers of several proinflammatory cytokines in the antigen-presenting cells such as interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF-alpha). As mast cells participate in the pathogenesis of several inflammatory skin disorders such as atopic dermatitis (AD), which is often aggravated by staphylococcal infections, we studied the effect of staphylococcal enterotoxin B (SEB) superantigen on the histamine release and IL-4 expression in a human mast-cell line (HMC-1). Incubation of SEB (50 micrograms/ml) with HMC-1 cells for 45 min, could not induce any histamine release. The HMC-1 cells were also stimulated with various concentrations of SEB (0, 1, 10, 20, 50 micrograms/ml) for 1, 2, 3 and 4 days. Clear dose-dependent inhibition of IL-4 protein production and release was observed on day 4 without any observed effect on cell viability. Compared with unstimulated HMC-1 cells, after 50 micrograms/ml SEB stimulation, the IL-4 mRNA levels decreased steadily in the 2, 6, 18 and 24 hr samples in repeated experiments as measured with the reverse transcription polymerase chain reaction (RT-PCR) method. In comparison, a biphasic decrease in TNF-alpha expression was found. Our results show that an human leukaemic mast cells, superantigen stimulation downregulates the production of IL-4.

Molecular basis of allergic diseases

This review examines our current understanding of the mechanisms underlying allergic diseases. The IgE molecule plays a central role in the pathogenesis of immediate hypersensitivity reactions by virtue of its capacity to bind specifically to high-affinity IgE receptors on mast cells and mediate the release of various mast cell-derived mediators and proinflammatory cytokines on exposure to allergen. Clinically significant allergic responses are followed by a late-phase response dominated by eosinophils and T lymphocytes. The majority of T cells in allergic responses are memory T cells secreting helper type 2 (TH2)-like cytokines, i.e., interleukin (IL)-4, IL-5, IL-13, but not interferon-gamma. These cytokines regulate IgE synthesis and promote eosinophil development, thus contributing to allergic inflammatory responses. Failure to control immune activation early in the course of allergic disease blunts responses to glucocorticoid therapy and contributes to disease progression. The identification of key cells and molecules involved in the initiation and maintenance of allergic inflammation is likely to become an important target in the treatment of this common group of illnesses.

Immunologic basis of chronic allergic diseases: clinical messages from the laboratory bench

During the past decade there have been significant advances in our understanding of the mechanisms underlying allergic responses. Immediate hypersensitivity reactions are mediated primarily by mast cells in an IgE-dependent manner. After the local release of various mediators, proinflammatory cytokines, and chemokines, there is a cell-mediated response that is dominated by eosinophils and T lymphocytes. The majority of T cells in early allergic reactions are memory T cells secreting helper type 2 (TH2)-like cytokines, i.e. IL-4, IL-5, and IL-13, but not interferon-gamma. These cytokines regulate IgE synthesis and promote eosinophil differentiation and cell survival, thus contributing to allergic inflammatory responses. Failure to control immune activation early in the course of allergic inflammation may blunt the response to glucocorticoid therapy and contribute to long-term morbidity of disease. The identification of key cells and cytokines involved in the initiation and maintenance of allergic inflammation is likely to become an important therapeutic target in the future management of this important group of diseases.

Nonspecific T-cell homing during inflammation in atopic dermatitis: expression of cutaneous lymphocyte-associated antigen and integrin alphaE beta7 on skin-infiltrating T cells

Atopic dermatitis (AD) is a chronic skin disorder, characterized by infiltration of activated memory CD4+ T cells into skin. A model to study the onset of allergic inflammation in a patient with AD is the atopy patch test (APT), in which, by epicutaneous application of aeroallergen, an eczematous reaction is induced in 50% of sensitized patients with AD. Extravasation of T cells into skin is thought to be critically dependent on expression of the surface molecule cutaneous lymphocyte-associated antigen (CLA), which recognizes and binds its ligand E-selectin on endothelium. We studied the dynamics of expression of CLA and the gut homing receptor alphaE beta7 (HML-1) on T cells in the skin of patients with AD and in APT reactions and nickel and sodium lauryl sulfate patch test reactions by means of immunohistochemical double staining of skin biopsy specimens. The results show an increase in the number of CD3+ T cells in the lesional skin of patients with AD, APT reactions, and nickel and sodium lauryl sulfate patch test reactions as compared with nonlesional skin of the same patients and nonatopic individuals. In contrast, the percentages of CLA+ T cells in the lesional skin of patients with AD, in the APT reactions, and in sodium lauryl sulfate and nickel patch test reactions were decreased. In addition, we found a marked expression of alphaE beta7 by T cells present in skin, indicating a nonspecific influx of T cells during allergic skin inflammation. We propose that during allergic skin inflammation CLA expression is not a prerequisite for cutaneous T-cell infiltration. CLA expression may be important for T cells to extravasate from blood into skin during immune surveillance or for retention of allergen-specific T cells in skin.

IgE-binding components of staphylococcal enterotoxins in patients with atopic dermatitis

BACKGROUND

The exacerbation of atopic dermatitis may be associated with infection of the skin with Staphylococcus aureus (S.aureus). S. aureus isolated from the skin of patients with atopic dermatitis secretes enterotoxin A, B, and toxic shock syndrome toxin 1. This is of interest because these patients may develop specific IgE antibodies against components from staphylococci.

OBJECTIVE

The objective was to demonstrate IgE-sensitization to components of Staphylococcus aureus enterotoxins A and B (purified and partially purified), toxic shock syndrome toxin 1, and the bacterial cell component lipoteichoic acid, in patients with atopic dermatitis.

METHODS

Blood samples from 34 patients with atopic dermatitis and 10 controls were tested by leukocyte histamine release to the enterotoxins and lipoteichoic acid. The toxins were separated by sodium dodecylsulfate polyacrylamide gel electrophoresis and analyzed by IgE-immunoblotting with sera from the same patients.

RESULTS

The majority of patients (96%) with clinical signs of skin infection produced specific IgE-antibodies to all three toxins. Nearly half of the patients produced IgE to enterotoxin A and B. Only 63% of the patients with atopic dermatitis showed cellular response judged by the release of histamine from patient basophils when challenged in vitro with the toxins. This may indicate clinically unimportant sensitization in a number of patients. The immunoblotting revealed that the major allergens of the toxins were 24 and 28 kD proteins. Partially purified toxins showed a higher frequency of leukocyte histamine release responses than purified toxin. The only obvious difference was a difference in the content of pure toxin of the two preparations. Lipoteichoic acid showed nonspecific activity.

CONCLUSION

These findings suggest that staphylococcal enterotoxins may act as specific allergens and induce IgE-antibodies to enterotoxins that may exacerbate the skin inflammation in some patients with atopic dermatitis.

Reduction of Staphylococcus aureus in atopic skin lesions with acid electrolytic water--a new therapeutic strategy for atopic dermatitis

The subjects studied were 22 pediatric patients newly diagnosed with atopic dermatitis (AD); 11 were treated with acid electrolytic water (AEW), which has a strong bactericidal activity (AEW group), and the other 11 with tap water (placebo group). AEW or tap water, 1 ml/cm2 (body surface area), was sprayed on their skin lesions with a spray gun each twice a day for a week. There were no significant differences between the two groups in regard to sex, age, serum IgE, peripheral eosinophil counts, grading scores of AD, and duration of AD. The study was designed as a randomized, placebo-controlled, double-blind clinical trial. Colony counts of Staphylococcus aureus on skin lesions in the AEW group, both 3 min after spraying (P < 0.05) and after 1 week of skin treatment (P < 0.01), were significantly decreased as compared with colony counts before treatment, while there was no significant difference in the placebo group before and after treatment. Grading scores of AD also decreased in the AEW group (P < 0.01), but not in the placebo group. Both the subjects' guardians' evaluation and a referee physician's evaluation of treatment effect were significantly higher in the AEW group than in the placebo group (P < 0.01). AEW may be potentially effective in preventing a staphylococcal chronic inflammation in AD because of its strong bactericidal activity.

Clinical role for a superantigen in Yersinia pseudotuberculosis infection

Yersinia pseudotuberculosis is an enteric pathogen that causes a variety of clinical symptoms in the human. Recently, we reported the production of a superantigen (Y. pseudotuberculosis-derived mitogen, YPM) by this organism and characterized the gene structure of ypm. To further study the potential pathogenic role of YPM in Y. pseudotuberculosis infection, we assayed IgG anti-YPM antibodies and T cell antigen receptor-Vbeta expression of the T cells in peripheral blood and in mesenteric lymph node in patients acutely infected with Y. pseudotuberculosis. 20 out of 33 patients (61%) had an elevated antibody titer compared with healthy controls (P = 0.0001). Patients with systemic symptoms such as lymphadenopathy, transient renal dysfunction, and arthritis had significantly higher titers of anti-YPM than patients with gastrointestinal tract symptoms alone. T cells bearing the Vbeta3 gene segment were significantly increased (P = 0.009) among acute phase patients compared with healthy children. During the convalescence phase of the illness, there was a reduction in the abnormal level of Vbeta3 T cells. Moreover, in the mesenteric lymph node, an elevated level of Vbeta3 T cells compared with peripheral blood and a sequence diversity in the junctional region of the T cell antigen receptor beta-chain containing Vbeta3 element was observed in one patient. Together, these findings suggest that YPM was produced in vivo and played an important role in the pathogenesis of Y. pseudotuberculosis infection.

Association of Erythrodermic Cutaneous T-Cell Lymphoma, Superantigen-Positive Staphylococcus aureus, and Oligoclonal T-Cell Receptor Vβ Gene Expansion

Forty-two patients with cutaneous T-cell lymphoma, including 31 with exfoliative erythroderma or Sezary syndrome and 11 with mycosis fungoides, were studied for the occurrence of staphylococcal infection. Thirty-two of 42 (76%) had a positive staphylococcal culture from skin or blood. One half of the patients with positive cultures grew Staphylococcus aureus. This group included 11 with Sezary syndrome and 5 with rapidly enlarging mycosis fungoides plaques or tumors. All of the S aureus carried enterotoxin genes. Surprisingly, 6 of 16 strains were the same toxic shock toxin-1 (TSST-1)-positive clone, designated electrophoretic type (ET)-41. Analysis of the T-cell receptor Vβ repertoire in 14 CTCL patients found that only 4 had the expected monoclonal expansion of a specific Vβ gene, whereas 10 had oligoclonal or polyclonal expansion of several Vβ families. All patients with TSST-1+S aureus had overexpansion of Vβ 2 in blood and/or skin lesions. These studies show that S aureus containing superantigen enterotoxins are commonly found in patients with CTCL, especially individuals with erythroderma where they could exacerbate and/or perpetuate stimulate chronic T-cell expansion and cutaneous inflammation. Attention to toxigenic S aureus in CTCL patients would be expected to improve the quality of care and outcome of this patient population.

Association of Erythrodermic Cutaneous T-Cell Lymphoma, Superantigen-Positive Staphylococcus aureus, and Oligoclonal T-Cell Receptor Vβ Gene Expansion

Forty-two patients with cutaneous T-cell lymphoma, including 31 with exfoliative erythroderma or Sezary syndrome and 11 with mycosis fungoides, were studied for the occurrence of staphylococcal infection. Thirty-two of 42 (76%) had a positive staphylococcal culture from skin or blood. One half of the patients with positive cultures grew Staphylococcus aureus. This group included 11 with Sezary syndrome and 5 with rapidly enlarging mycosis fungoides plaques or tumors. All of the S aureus carried enterotoxin genes. Surprisingly, 6 of 16 strains were the same toxic shock toxin-1 (TSST-1)-positive clone, designated electrophoretic type (ET)-41. Analysis of the T-cell receptor Vβ repertoire in 14 CTCL patients found that only 4 had the expected monoclonal expansion of a specific Vβ gene, whereas 10 had oligoclonal or polyclonal expansion of several Vβ families. All patients with TSST-1+S aureus had overexpansion of Vβ 2 in blood and/or skin lesions. These studies show that S aureus containing superantigen enterotoxins are commonly found in patients with CTCL, especially individuals with erythroderma where they could exacerbate and/or perpetuate stimulate chronic T-cell expansion and cutaneous inflammation. Attention to toxigenic S aureus in CTCL patients would be expected to improve the quality of care and outcome of this patient population.

Staphylococcal toxins and protein A differentially induce cytotoxicity and release of tumor necrosis factor-alpha from human keratinocytes

It has been proposed that toxins and other bacterial protein products of Staphylococcus aureus can act as triggers or persistence factors in several inflammatory skin diseases. In this study, we examined the S. aureus isolates from the skin of patients with atopic dermatitis and psoriasis. We found that the bacterial isolates from these patients exhibited either characteristic superantigenic toxins or thermolabile toxins believed to be staphylococcal alpha-toxin. All of these staphylococcal strains also secreted extracellular staphylococcal protein A. We found significant differences in the action of these toxins on human keratinocytes and keratinocyte cell lines. The superantigenic toxins toxic shock syndrome toxin-1, staphylococcal enterotoxins A and B, and exfoliative toxin-A, as well as staphylococcal protein A, did not induce significant cytotoxic damage in the keratinocyte cell line HaCaT, whereas the staphylococcal alpha-toxin produced profound cytotoxicity. Keratinocyte cytotoxicity induced by staphylococcal alpha-toxin was time and concentration dependent and demonstrated the morphologic and functional characteristics of necrosis, not apoptosis. Addition of alpha-toxin to keratinocytes simultaneously induced cell lysis and tumor necrosis factor-alpha release into the medium within 30 min; apparently, it was constitutive tumor necrosis factor-alpha. On the other hand, superantigenic toxins and, in particular, protein A showed stimulation of tumor necrosis factor-alpha secretion in keratinocytes and release of this cytokine after 6-12 h of incubation. Thus, staphylococcal protein A, alpha-toxin, and superantigenic toxins found in S. aureus isolates from patients with psoriasis and atopic dermatitis can produce direct pro-inflammatory effects on keratinocytes through the release of tumor necrosis factor-alpha. We propose that these effects may be relevant to the induction and persistence of lesions in these two diseases.

Role of staphylococcal enterotoxins in pathogenesis of atopic dermatitis: growth and expression of T cell receptor V beta of peripheral blood mononuclear cells stimulated by enterotoxins A and B

In order to investigate the role of staphylococcal enterotoxins in the pathogenesis of dermatitis in atopic patients, the growth and expression of T cell receptor V beta in peripheral blood mononuclear cells (PBMCs) from atopic dermatitis patients induced by stimulation with staphylococcal enterotoxin A (SEA) or staphylococcal enterotoxin B (SEB) were examined. Lymphocyte stimulation tests (LST) using SEA or SEB were performed in atopic dermatitis (AD) patients (n = 10) and normal controls (n = 5). PBMCs from AD patients displayed significantly stronger responses to SEA or SEB than those from the controls. To ascertain further whether SEA acts as a superantigen in atopic dermatitis, the expression of 22 genes in the variable region of the beta chain (V beta) of T cell receptors (TcR) was examined before and after stimulation with SEA by a reverse transcriptase-polymerase chain reaction (RT-PCR). Before stimulation, only weak expression of V beta was observed, and the expression of the various V beta segments was uniform in the normal controls (n = 3). In the AD patients (n = 3), the expression of V beta was enhanced, but was not uniform in 2 out of 3 patients and the pattern of expression was characteristic in each individual. This suggests that V beta expression varies in individual AD patients and displays restricted heterogeneity, reflecting the diversity of the etiology of the disease. After culture of the SEA-stimulated cells, no difference was observed in the expression of TcR V beta segments in the 3 normal controls as compared with that prior to stimulation, but particular V beta segments were intensely expressed in 3 AD patients, displaying distinct patterns (case I: V beta 9, V beta 10, V beta 18; case 2: V beta 6.1-3; case 3: V beta 6.1-3, V beta 18). Many of these V beta segments corresponded with those known to be induced by SEA. These results suggest oligoclonal proliferation of T cells in the peripheral blood of AD patients and high responsiveness in each clone, and since the expression of V beta segment after SEA stimulation was restricted, the actions of staphylococcal enterotoxins as superantigens were suggested.

Differential effects of staphylococcal toxic shock syndrome toxin-1 on B cell apoptosis

Superantigens, such as toxic shock syndrome toxin 1 (TSST-1), have been implicated in the pathogenesis of several autoimmune and allergic diseases associated with polyclonal B cell activation. In this report, we studied the in vitro effects of TSST-1 on B cell activation. We show herein that TSST-1 produced antagonistic effects on Ig synthesis by peripheral blood mononuclear cells (PBMC) from normal subjects, depending on the concentration used; Ig production was inhibited at 1000 pg/ml (P < 0.01) and enhanced at 1 and 0.01 pg/ml (P < 0.01) of toxin. Cultures of PBMC were then examined for morphologic features and DNA fragmentation characteristic for apoptosis. B cells exhibited a significantly higher (P < 0.01) incidence of apoptosis after stimulation with 1000 pg/ml of TSST-1 compared with 1 or 0.01 pg/ml of toxin or medium alone. Abundant expression of Fas, a cell surface protein that mediates apoptosis, was detected on B cells after stimulation with 1000 pg/ml of TSST-1 and was significantly higher on B cells undergoing apoptosis than on live cells (P = 0.01). Additionally, increased Fas expression and B cell death occurred at concentrations of TSST-1 inducing the production of high amounts of gamma interferon (IFN-gamma), and both events could be blocked by neutralizing anti-IFN-gamma antibody. These findings suggest that high concentrations of TSST-1 can induce IFN-gamma-dependent B cell apoptosis, whereas at low concentrations it stimulates Ig synthesis by PBMC from normal subjects. These findings support the concept that staphylococcal toxins have a role in B cell hyperactivity in autoimmunity and allergy.

Cutaneous exposure to the superantigen staphylococcal enterotoxin B elicits a T-cell-dependent inflammatory response

We analyzed the impact of superantigens secreted by skin-colonizing Staphylococci on the skin and the associated lymphoid tissue following epicutaneous application and intracutaneous injection of small amounts of staphylococcal enterotoxin B (SEB). A single intracutaneous injection of 50 ng of SEB elicited a strong inflammatory response in the skin of BALB/c mice. Three to 6 h later, we observed langerhans cell activation, mast cell degranulation, vasodilation, upregulation of ICAM-1, and induction of VCAM-1 on dermal blood vessels, with vascular adhesion of granulocytes. by 12 to 24 h, cell infiltration of the dermis increased, reaching the epidermis. Among the infiltrating leukocytes, a substantial number of eosinophils was found. After 48 h, the infiltrate was dominated by mononuclear cells. The response to SEB was dose-dependent, and signs of inflammation slowly disappeared over 5 to 7 days. Although the induction of VCAM-1 on dermal blood vessels suggested a role for interleukin-1/tumor necrosis factor-alpha in this reaction, the activation of monocytes/macrophages was not able to substitute for lymphocytes, as severe combined immunodeficiency (SCID) mice (which are lymphocyte-deficient) did not mount an inflammatory skin response to intradermal injection of SEB. The fact that nude mice (T-cell-deficient) also did not mount an inflammatory response to SEB indicated the T-cell dependency of the response. The V beta specificity of the SEB effect was demonstrated by the fact that SJL/J mice, which lack V beta 8+ T cells (the major SEB-reactive T cell population in mice), exhibited much weaker responses. Deletion or tolerization of SEB-reactive V beta T cells was not observed after a single intradermal injection of such minute amounts of SEB.

Superantigens

Superantigens are potent modulators of the immune system. Some of their biological and immunological properties are reviewed here with special attention to their potential significance for cutaneous inflammation, specific skin immune responses and skin diseases.

New perspectives on inflammation in atopic dermatitis

Recent information implicates the stimulation of T cells by Staphylococcus aureus antigens and exotoxins as a likely factor in provoking the inflammatory response in atopic dermatitis. S. aureus secrets exotoxins called superantigens, which stimulate a large proportion of T cells. In addition, protein A, a component of the cell wall of S. aureus, is a potent B cell mitogen. This understanding provides a rationale for attempting to reduce the staphylococcal skin colonization of patients with severe atopic dermatitis and correlates with the clinical observation in a number of situations of marked improvement in atopic dermatitis following antibiotic treatment.

Atopic dermatitis: is it an allergic disease?

For many years controversy has surrounded the relation between allergy and atopic dermatitis. We critically review the evidence for the contribution of allergy, or IgE-mediated hypersensitivity reactions, to the pathogenesis of this disease. We conclude that, at present, there is scant evidence that allergy is central to the development of atopic dermatitis, although it may be an aggravating factor in a few patients. Hence there is little rationale for the routine use of allergy testing or dietary and environmental manipulation in the management of this disease.

Role and modulation of T-cell cytokines in allergy

Allergic sensitization and the development of effector functions are controlled by IL-4-secreting and IL-5-secreting type 2 T cells. Recent studies have provided new insights into the events triggering the development of type 1 and type 2 T cells, the discrimination of type 1 and type 2 effector T cells from various T-cell subsets, and the improvement of established and new therapeutic strategies, which are aimed at modulating such T-cell functions in the allergic patient.

Upregulation of IgE synthesis by staphylococcal toxic shock syndrome toxin-1 in peripheral blood mononuclear cells from patients with atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a chronic skin disease associated with increased IgE synthesis and colonization with Staphylococcus aureus secreting exotoxins, such as Toxic Shock Syndrome Toxin-1 (TSST-1).

OBJECTIVES

In this study, we were interested in determining the in vitro effects of TSST-1 on IgE synthesis in peripheral blood mononuclear cells from patients with AD.

METHODS

We stimulated peripheral blood mononuclear cells (PBMC) from AD patients with a wide range of TSST-1 concentrations and measured IgE synthesis by enzyme-linked immunosorbent assay (ELISA) after 14 days.

RESULTS

We show herein that TSST-1 produced antagonistic effects on IgE synthesis by PBMC from AD patients, depending on the concentration used: IgE synthesis was inhibited at 1000 pg/mL (P < 0.05) and enhanced at 0.01 pg/mL (P < 0.01) of toxin. TSST-1 was found to induce the production of much higher amounts of interferon-gamma (IFN gamma) at 1000 pg/mL than at 0.01 pg/mL of toxin (P = 0.0001). More importantly, immunoglobulin E (IgE) synthesis was enhanced by TSST-1 at 1 pg/mL in the presence of antibodies blocking IFN gamma activity. The other immunoglobulin (Ig) isotypes were also increased after TSST-1 stimulation suggesting that the enhanced IgE synthesis was secondary to a polyclonal B cell activation rather than an isotype switch. TSST-1-stimulated IgE synthesis was T cell-dependent because purified tonsil B cells were only able to synthesize increased amounts of IgE when small numbers of T cells were added to the cultures. Anti-HLA-DR and anti-LFA-1 monoclonal antibodies (MoAb) inhibited TSST-1-enhanced IgE synthesis, suggesting that the bridging of the T cell receptor (TCR) and major histocompatibility complex (MHC) class II on B cells was necessary for activation of B cell differentiation.

CONCLUSION

These data indicate that staphylococcal superantigens are able, at concentrations inducing low amounts of IFN gamma, to stimulate IgE synthesis by PBMC from AD patients, and suggest that staphylococcal toxins may contribute to elevated IgE synthesis in AD.

The potential role of bacterial superantigens in the pathogenesis of Kawasaki syndrome

Kawasaki syndrome is an acute multisystem vasculitis of infancy and early childhood associated with high fever, mucocutaneous inflammation, and the development of coronary artery abnormalities. Despite the widely held belief that Kawasaki syndrome is an infectious disease, investigations have failed to identify a causal organism. Previous studies have demonstrated that this illness is associated with marked activation of monocyte/macrophages and the selective expansion of V beta 2-, less so, of V beta 8.1/8.2-expressing T cells in the peripheral blood from Kawasaki syndrome patients during the acute phase of their illness. These immunologic features are characteristic of diseases that are caused by bacterial toxins which act as superantigens. Staphylococcal enterotoxins and streptococcal exotoxins are prototypic superantigens which stimulate large populations of T cells expressing particular T-cell receptor beta-chain variable (V beta) gene segments. Using the V beta 2+ T-cell expansion as an "immunologic footprint" for a superantigen, we have extended these observations to the identification and isolation of a novel clone of toxic shock syndrome toxin-1-producing Staphylococcus aureus in the majority of patients with Kawasaki syndrome and streptococcal pyrogenic exotoxin B/streptococcal pyrogenic exotoxin C-producing streptococci in a minority of Kawasaki syndrome patients. Toxic shock syndrome toxin-1, streptococcal pyrogenic exotoxin B, and streptococcal pyrogenic exotoxin C are known to stimulate V beta 2+ T cells. These observations support the hypothesis that the activation of V beta 2+ T cells during the acute phase of Kawasaki syndrome is caused by bacterial superantigen(s).

Atopic dermatitis: new knowledge and new approaches

Appreciation of the role of allergens in atopic dermatitis has at least two therapeutic implications: Avoidance of identified allergens may reduce or even eliminate the need for other treatments. On the other hand, circumstances such as fungal colonization may maintain symptoms even when other causative factors have been addressed.

Modulation of contact sensitivity responses by bacterial superantigen

Superantigens are potent modulators of the immune system, especially T cells. Therefore, we determined the influence of superantigens on the T-cell-mediated immune response, contact sensitivity. We chose the combination of staphylococcal enterotoxin B (SEB) as superantigen and 2,4-dinitrofluorbenzene (DNFB) as the contact sensitizer, because in BALB/c mice SEB reacts almost exclusively with V beta 8+ T cells, and these cells are capable of transferring contact sensitivity to DNFB from sensitized donors to naive syngeneic recipients. Pretreatment with a single intradermal injection of 50 ng SEB 24 h before DNFB exposure at the same site on the lower abdomen enhanced the induction of contact sensitivity: its intradermal injection permitted sensitization with non-sensitizing concentrations of DNFB as assessed by ear swelling responses after challenge with DNFB. In contrast, pretreatment with repeated intradermal injections of 50 ng SEB every other day over at least 1 week inhibited the induction of contact sensitivity following sensitization. The enhancing effect of SEB may be explained by the creation of a proinflammatory milieu in the skin after a single intradermal injection of the bacterial toxin, whereas the inhibitory effect may be due to tolerization of V beta 8+ T cells. The data indicate that products of skin-colonizing bacteria that can serve as superantigens are able to augment or inhibit the development of contact sensitivity.

The role of superantigens in skin disease

Staphylococcus aureus and streptococci secrete a large family of exotoxins involved in the pathogenesis of toxic-shock-like syndromes and have been implicated in several autoimmune disorders. These toxins act as prototypic superantigens capable of binding to major histocompatibility complex proteins on antigen-presenting cells outside the antigen peptide-binding groove and can thereby stimulate cytokine release from macrophages. The superantigen-major histocompatibility complex unit is recognized primarily by the variable region of the T-cell receptor beta chain, and by engaging this region, can activate a large portion of the T-cell repertoire. It is thought that the capacity of these toxins to cause the massive stimulation of T cells and accessory cells such as macrophages, Langerhans cells, and activated keratinocytes accounts for most of their pathologic effects. The current review examines the evidence that implicates a role for these superantigens in the pathogenesis of certain skin diseases.

Human immunodeficiency virus and the skin: selected controversies

Acquired immunodeficiency syndrome was first recognized as a new disease in 1981 because of the unusual association of Kaposi's sarcoma and Pneumocystis carinii pneumonia in young men. The skin remains one of the most important clinical markers for acquired immunodeficiency syndrome, now recognized as the end stage of infection with the human immunodeficiency virus (HIV). Indeed, an urticarial viral exanthem appearing during seroconversion may allow early identification of newly infected individuals who might benefit from administration of antiviral therapy during plasma viremia. The "asymptomatic HIV infection" is often accompanied by multiple skin complaints, which commonly include xerosis, pruritus, psoriasis/seborrheic dermatitis, and pruritic papular eruptions, the cause of which remains controversial. Psoriasis and Kaposi's sarcoma lesions share features including angiogenesis, dermal dendrocytes infected with HIV, and epidermal hyperproliferation, and are manifested by mice transgenic for HIV provirus or Tat-ltr. Changes in the immune system including T-cell function, antigen response, and shifting cytokine expression as well as a propensity for autoimmune reactions must underlie the skin immunodysfunction occurring in the setting of HIV infection. One of the most unsettling controversies suggested by in vitro data is that ultraviolet light, an effective therapy for HIV-related skin disorders, may actually activate the virus.

Role of a carboxy-terminal site of toxic shock syndrome toxin 1 in eliciting immune responses of human peripheral blood mononuclear cells

Staphylococcus aureus toxic shock syndrome toxin 1 (TSST-1) is involved in the pathogenesis of toxic shock syndrome and perhaps other staphylococcal diseases. Recently, the C-terminal part of the TSST-1 toxin has been shown to be responsible for mitogenic activity in animal models. We studied the role of the C-terminal structural unit of TSST-1 with regard to proliferation, cytokine release (tumor necrosis factor alpha [TNF-alpha], interleukin-6 [IL-6], and IL-8), mRNA expression for IL-6, IL-8, IL-10, TNF-alpha, and CD40 ligand (CD40L), synthesis of immunoglobulin E (IgE), IgA, IgG, and IgM, CD23 expression, and soluble CD23 (sCD23) release from human peripheral blood mononuclear cells (PBMC). For this purpose, we used the recombinant wild-type TSST-1 (p17) mutant toxin Y115A (tyrosine residue modified to alanine) and toxin H135A (histidine residue modified to alanine). Unmodified toxin p17 and mutant toxin Y115A, at a concentration below 5 ng, to a lesser degree, induced a strong proliferation. Toxin p17 followed by toxin Y115A was the most pronounced inducer for mRNA expression for IL-10 and CD40L and cytokine generation (mRNA and protein) for TNF-alpha, IL-6, and IL-8. Mutant protein H135A failed to activate human PBMC. Both toxins p17 and, to a lesser degree, Y115A significantly suppressed IL-4- and anti-CD40-induced synthesis of all four Igs as well as IL-4-induced CD23 expression and sCD23 release. Mutant toxin H135A failed to do so. Thus, our data show that a region in the C terminus of TSST-1 is responsible not only for mitogenic activity but also for additional immunomodulating biological activities of TSST-1. More specifically, histidine residue H135A of the 194-amino-acid toxin appears to be critical for the expression of biological activities in a human in vitro model.

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

T lymphocyte infiltration is a prominent feature of the skin inflammation associated with infections by toxin (superantigen)-secreting Staphylococcus aureus or Streptococcus bacteria. The cutaneous lymphocyte-associated antigen (CLA) has been hypothesized to be a homing receptor (HR) involved in selective migration of memory/effector T cells to the skin. Since the expression of this putative skin-selective HR is known to be under strict microenvironmental control, we sought to determine the effect of staphylococcal and streptococcal toxins on T cell expression of CLA. After in vitro stimulation of peripheral blood mononuclear cells with staphylococcal enterotoxin B, toxic shock syndrome toxin-1, and streptococcal pyrogenic exotoxins A and C, there was a significant increase in the numbers of CLA+ T cell blasts (p < 0.01), but not blasts bearing the mucosa-associated adhesion molecule alpha e beta 7-integrin, compared with T cells stimulated with phytohemaglutinin (PHA) or anti-CD3. Bacterial toxins were also found to specifically induce interleukin (IL) 12 production. More importantly, induction of toxin-induced CLA expression was blocked by anti-IL-12, and the addition of IL-12 to PHA-stimulated T cells induced CLA, but not alpha e beta 7-integrin, expression. These data suggest that bacterial toxins induce the expansion of skin-homing CLA+ T cells in an IL-12-dependent manner, and thus may contribute to the development of skin rashes in superantigen-mediated diseases.

The role of mast cells in inflammatory reactions of the airways, skin and intestine

The concept that mast cells play a key role in the initiation of acute allergic responses has been around for many years. However, the role of mast cells in the chronic processes that are the hallmark of inflammatory disease is still poorly understood. With better techniques to study mast cell function it has become clear that these cells may have a much wider role in immune responses and regulation than previously recognized. Exciting progress has been made over the past year in defining the breadth of mast cell functions in inflammation. Further studies are necessary to evaluate the in vivo significance of many of these findings.

Role of IgE in atopic dermatitis

Atopic dermatitis is a chronic inflammatory skin disease associated with elevated serum IgE levels and sensitization to a variety of inhalant, food and microbial allergens. Controlled challenges have provided substantial evidence that allergens can trigger acute IgE-mediated mast-cell dependent exacerbations of eczema in these patients. However, the sustained chronic skin inflammation that characterizes atopic dermatitis is likely to result from a local expansion of allergen-specific T helper type 2 cells that produce interleukin-4 and interleukin-5 and the concomitant infiltration of eosinophils. An important role for IgE in allergen presentation to T helper type 2 cells by Langerhans cells has been proposed. These observations may have important implications for the development of new approaches for the treatment of this increasingly common allergic disorder.