Superantigenic staphylococcal exotoxins induce T-cell proliferation in the presence of Langerhans cells or class II-bearing keratinocytes and stimulate keratinocytes to produce T-cell-activating cytokines

Identification of IL-27 as a novel regulator of major histocompatibility complex class I and class II expression, antigen presentation, and processing in intestinal epithelial cells

Antigen presentation via major histocompatibility complex (MHC) class I and class II receptors plays a fundamental role in T cell-mediated adaptive immunity. A dysregulation of this fine-tuned recognition might result in the development of autoimmune diseases such as inflammatory bowel diseases that are characterized by chronic relapsing inflammation of the intestinal tract and a damaged intestinal epithelial barrier. While MHCII receptors are usually expressed by professional antigen presenting cells (APC) only, there is increasing evidence that non-immune cells such as intestinal epithelial cells (IEC) might express MHCII upon stimulation with IFN-γ and thus act as non-professional APC. However, little is known about other factors regulating intestinal epithelial MHC expression. Here, we identify IL-27 as an inducer of different MHCI and MHCII receptor subtypes and the invariant chain (CD74/li) in IEC via the STAT1/IRF1/CIITA axis. CIITA, MHCII, and CD74 expression was significantly increased in IEC from Crohn's disease (CD) patients with active disease compared to controls or CD patients in remission. IEC phagocytosed and digested external antigens and apoptotic cells. IL-27 strongly stimulated antigen processing via the immunoproteasome in a IRF1-dependent manner. In co-culture experiments, antigen-primed IEC strongly enhanced lymphocyte proliferation and IL-2 secretion, dependent on direct cell-cell contact. IL-27 pretreatment of IEC significantly increased CD4+ T cell proliferation and reduced IL-2 levels in lymphocytes in coculture. In summary, we identified IL-27 as a novel regulator of IEC antigen processing and presentation via MHCI and MHCII receptors, underscoring the importance of IEC as non-professional APC.

Mechanisms of microbial pathogenesis and the role of the skin microbiome in psoriasis: A review

The pathogenesis of psoriasis may involve a breakdown of immune tolerance to cutaneous microorganisms. Psoriasis is associated with a higher incidence of Crohn disease and periodontitis, two diseases involving impaired tolerance and abnormal immune activation in response to intestinal and oral microbiota, respectively. In addition, guttate and chronic plaque psoriasis are associated with Streptococcus pyogenes colonization. The aim of this review is to characterize the microorganisms implicated in psoriasis by examining results of major association studies and possible mechanisms of pathogenesis. Although studies show relative increases in Streptococcus and Staphylococcus and decreases in Malassezia and Cutibacterium, they differ in methods of sampling and methods of microbial analysis. As such, no definitive associations between microbes and psoriasis have been found to date. It also remains unclear if changes in the microbiomal composition have a causal association with psoriasis or are simply a consequence of the inflammatory microenvironment. Techniques enabling strain-level analysis rather than species-level analysis of the skin microbiome are likely necessary to determine microbiomal signatures of psoriasis. Future investigations may lead to new diagnostic tests and novel treatments, such as probiotics or bacterial transplantation.

Secreted immunoregulatory proteins in the skin

The skin, thought initially to protect the body passively from pathogenic organisms and other environmental insults, is now recognised additionally as a sophisticated immune organ that actively regulates local immunity. Studies linking local innate and adaptive immunity to skin health and disease have revealed a complex network of cell communication and cytokine signalling. Here, we review the last 10 years of literature on this topic, and its relevance to skin immunity.

IL-23 from Langerhans cells is required for the development of imiquimod-induced psoriasis-like dermatitis by induction of IL-17A-producing γδ T cells

Psoriasis is a common chronic inflammatory skin disease that involves dysregulated interplay between immune cells and keratinocytes. Recently, it has been reported that IL-23 induces CCR6+ γδ T cells, which have the pivotal role in psoriasis-like skin inflammation in mice of producing IL-17A and IL-22. Langerhans cells (LCs) are a subset of dendritic cells that reside in the epidermis and regulate immune responses. The role of LCs has been extensively investigated in contact hypersensitivity, but their role in psoriasis remains to be clarified. In this study, we focused on Th17-related factors and assessed the role of LCs and γδ T cells in the development of psoriasis using a mouse psoriasis model triggered by topical application of imiquimod (IMQ). LC depletion by means of diphtheria toxin (DT) in Langerin DT receptor-knocked-in mice suppressed hyperkeratosis, parakeratosis, and ear swelling in the IMQ-treated regions. In addition, LC-depleted mice showed decreased levels of Th17-related cytokines in IMQ-treated skin lesions. Moreover, the IMQ-treated skin of LC-depleted mice showed a decreased number of IL-17A-producing CCR6+ γδ T cells. These results suggest that LCs are required for the development of psoriasis-like lesions induced by IMQ in mice.

A model of an integrated immune system pathway in Homo sapiens and its interaction with superantigen producing expression regulatory pathway in Staphylococcus aureus: comparing behavior of pathogen perturbed and unperturbed pathway

Response of an immune system to a pathogen attack depends on the balance between the host immune defense and the virulence of the pathogen. Investigation of molecular interactions between the proteins of a host and a pathogen helps in identifying the pathogenic proteins. It is necessary to understand the dynamics of a normally behaved host system to evaluate the capacity of its immune system upon pathogen attack. In this study, we have compared the behavior of an unperturbed and pathogen perturbed host system. Moreover, we have developed a formalism under Flux Balance Analysis (FBA) for the optimization of conflicting objective functions. We have constructed an integrated pathway system, which includes Staphylococcal Superantigen (SAg) expression regulatory pathway and TCR signaling pathway of Homo sapiens. We have implemented the method on this pathway system and observed the behavior of host signaling molecules upon pathogen attack. The entire study has been divided into six different cases, based on the perturbed/unperturbed conditions. In other words, we have investigated unperturbed and pathogen perturbed human TCR signaling pathway, with different combinations of optimization of concentrations of regulatory and signaling molecules. One of these cases has aimed at finding out whether minimization of the toxin production in a pathogen leads to the change in the concentration levels of the proteins coded by TCR signaling pathway genes in the infected host. Based on the computed results, we have hypothesized that the balance between TCR signaling inhibitory and stimulatory molecules can keep TCR signaling system into resting/stimulating state, depending upon the perturbation. The proposed integrated host-pathogen interaction pathway model has accurately reflected the experimental evidences, which we have used for validation purpose. The significance of this kind of investigation lies in revealing the susceptible interaction points that can take back the Staphylococcal Enterotoxin (SE)-challenged system within the range of normal behavior.

Induction of eosinophil- and Th2-attracting epidermal chemokines and cutaneous late-phase reaction in tape-stripped skin

Skin barrier damage induces various harmful or even protective reactions in the skin, as represented by enhancement of keratinocyte cytokine production. To investigate whether acute removal of stratum corneum modulates the production of chemokines by epidermal cells, we treated ears of BALB/c and C57BL/6 mice by tape-stripping, or acetone-rubbing as a control of acute barrier disruption procedure. There was no difference between the tape-stripped and acetone-rubbed skin sites in the increased and recovered levels of transepidermal water loss. The mRNA expression levels of all the chemokines tested, including Th1 chemokines (CXCL10, CXCL9 and CXCL11), Th2 chemokines (CCL17 and CCL22) and eosinophil chemoattractant (CCL5), were higher in the epidermal cells from BALB/c than in those of C57BL/6 mice. In particular, CCL17, CCL22 and CCL5 were remarkably elevated in BALB/c mice and augmented by tape-stripping more markedly than acetone-rubbing, whereas Th1 chemokines were enhanced by acetone-rubbing more remarkably. Tape-stripping induced dermal infiltration of eosinophils in BALB/c but not C57BL/6 mice. In a contact hypersensitivity model, where BALB/c mice were sensitized on the abdomen and challenged on the ears with fluorescein isothiocyanate, mice exhibited higher ear swelling responses at the late-phase as well as delayed-type reactions, when challenged via the tape-stripped skin. The challenge via tape-stripped skin augmented the expression of IL-4 and CCR4 in the skin homogenated samples, indicating infiltration of Th2 cells. These findings suggest that acute barrier removal induces the expression of Th2 and eosinophil chemokines by epidermal cells and easily evokes the late phase reaction upon challenge with antigen.

Inducible nitric oxide synthase downmodulates contact hypersensitivity by suppressing dendritic cell migration and survival

Nitric oxide (NO) has several important roles in various physiological settings; one of the NO synthases, inducible NO synthase (iNOS), is induced by external stimulation of the skin. A prototypic example of external stimulation is hapten exposure, which induces the T-cell-mediated immune response known as contact hypersensitivity (CHS). We herein report on cutaneous dendritic cell (DC) function in the presence of an iNOS-specific inhibitor during the sensitization phase of CHS. First, we examined epidermal cell (EC) suspensions using flow cytometry with an iNOS antibody and confirmed that iNOS was expressed in the cytoplasm of Langerhans cells (LCs). We then studied the role of iNOS in CHS, and found that responses to DNFB were enhanced by the addition of an iNOS inhibitor during sensitization. Similarly, the iNOS inhibitor augmented FITC-induced migration of cutaneous DCs, including Langerin(+) LCs and Langerin(-) dermal DCs, to draining lymph nodes. Finally, we showed that iNOS inhibitor enhanced LC survival in vitro. We concluded that NO suppresses migration and survival of cutaneous DCs, resulting in a downmodulation of CHS.

Skin application of the nonsteroidal anti-inflammatory drug ketoprofen downmodulates the antigen-presenting ability of Langerhans cells in mice

BACKGROUND

Ketoprofen (KP) is widely used as a topical nonsteroidal anti-inflammatory drug that inhibits prostaglandin (PG) biosynthesis. As PGE(2) upregulates the antigen-presenting activity of Langerhans cells (LCs), i.e. migration to lymph nodes and expression of immunocompetent molecules, modulation of LC functions resulting from topical application of KP is an issue to be clarified.

OBJECTIVES

To investigate the in vivo effect of KP application to the skin and the in vitro effect of KP addition to the culture on the antigen-presenting ability of murine LCs. Methods Ears of BALB/c mice were painted with picryl chloride (PCl) hapten, KP or both. An immunofluorescence study of epidermal sheets and a flow cytometric analysis of epidermal cell suspensions from the treated ears were performed.

RESULTS

PCl altered the morphology of LCs and reduced their number, and simultaneous application of 10% KP maintained LC morphology and number. KP at 5% or 10% clearly decreased the PCl-augmented expression of major histocompatibility complex class II and CD86 on LCs. In cultivation of freshly isolated epidermal cells, 5 mmol L(-1) KP inhibited the culture-promoted expression of these molecules on LCs, whereas 100 micromol L(-1) indomethacin was not inhibitory. The further addition of PGE(2) to the KP-containing epidermal cell culture did not restore the expression of these molecules. Moreover, topical application of 10% KP to the sensitizing sites suppressed the development of contact hypersensitivity to PCl.

CONCLUSIONS

KP may have the potential to inhibit the antigen-presenting ability of LCs, in a PGE(2)-independent manner.

Stimulation of Langerhans cells with ketoprofen plus UVA in murine photocontact dermatitis to ketoprofen

BACKGROUND

Ketoprofen (KP) clinically evokes the allergic type of photocontact dermatitis when applied to the skin and irradiated with ultraviolet A (UVA). We have established a murine model of photocontact dermatitis to KP, which is a T cell-mediated delayed type hypersensitivity.

OBJECTIVE

To further explore the mechanism underlying this sensitivity, we investigated whether KP plus UVA activates the antigen-presenting ability of Langerhans cells (LCs).

METHODS

We analyzed the expression of surface molecules on LCs in the murine epidermis treated with KP plus UVA by immunohistochemistry and flow cytometry. Changes in the cytokine expression of epidermal cells from KP-phototreated skin were also examined by real-time PCR.

RESULTS

LCs became larger after treatment with KP plus UVA. The number of LCs was significantly decreased 2-3 days after KP phototreatment and recovered on day 5. A flow cytometric analysis revealed that KP plus UVA increased the percentage of LCs that highly expressed MHC class II, CD86, CD80, CD54 and CD40, whereas neither KP nor UVA alone enhanced the expression. KP phototreatment augmented the expression of I-A and CD86 on LCs in KP and UVA dose-dependent manners. A real-time PCR analysis of KP-phototreated skin showed that the expression of mRNA for IL-1alpha and GM-CSF was immediately increased after treatment.

CONCLUSION

A photosensitizing regimen of KP plus UVA activates LCs at least partly by stimulating keratinocytes to produce cytokines. Two strains of mice (BALB/c and AKR) differ in responsiveness to KP and the difference is not related to the activation of keratinocytes.

CXCR4 engagement promotes dendritic cell survival and maturation

It has been reported that human monocyte derived-dendritic cells (DCs) express CXCR4, responsible for chemotaxis to CXCL12. However, it remains unknown whether CXCR4 is involved in other functions of DCs. Initially, we found that CXCR4 was expressed on bone marrow-derived DCs (BMDCs). The addition of specific CXCR4 antagonist, 4-F-Benzoyl-TN14003, to the culture of mouse BMDCs decreased their number, especially the mature subset of them. The similar effect was found on the number of Langerhans cells (LCs) but not keratinocytes among epidermal cell suspensions. Since LCs are incapable of proliferating in vitro, these results indicate that CXCR4 engagement is important for not only maturation but also survival of DCs. Consistently, the dinitrobenzene sulfonic acid-induced, antigen-specific in vitro proliferation of previously sensitized lymph node cells was enhanced by CXCL12, and suppressed by CXCR4 antagonist. These findings suggest that CXCL12-CXCR4 engagement enhances DC maturation and survival to initiate acquired immune response.

The constitutive capacity of human keratinocytes to kill Staphylococcus aureus is dependent on beta-defensin 3

Normal skin is often exposed to bacteria, including potent pathogens such as E. coli, Staphylococcus aureus, and Streptococcus sp., but these microbes usually do not cause skin inflammation or infection in healthy individuals. Therefore, we hypothesized that there must be a constitutive mechanism for rapid destruction and elimination of small numbers of bacteria which penetrate the stratum corneum from everyday activities. This study found that exposure of keratinocytes cultured from a number of individuals to S. aureus resulted in approximately 2-3 log better killing than by HaCaT cells within 1 hour. Killing required contact between the keratinocytes and the bacteria, but was not dependent on internalization. Contact between the bacteria and the keratinocytes resulted in rapid deposition of several antimicrobial peptides onto the bacteria, but only human beta-defensin (HBD) 3 accumulated at levels sufficient to account for killing when S. aureus were exposed to human skin explants. Blocking peptide binding of HBD3 inhibited killing of the bacteria, indicating an essential role for beta-defensin 3 in the constitutive killing of bacteria by normal keratinocytes.

Innate immunity mediated by epidermal keratinocytes promotes acquired immunity involving Langerhans cells and T cells in the skin

Skin is an immunological organ consisting of epidermal cells, i.e. keratinocytes and Langerhans cells (LCs, antigen-presenting dendritic cells), and both innate and acquired immune systems operate upon exposure of the skin to various external microbes or their elements. To explore the relationship between innate and acquired immunities in the skin, we investigated whether Toll-like receptor (TLR) ligation of epidermal cells enhances the ability of LCs to present a specific antigen to T cells in mice. LC-containing epidermal cells were incubated with CpG oligonucleotide (TLR9 ligand) modified with trinitrophenyl hapten, and cultured with hapten-primed CD4(+) T cells. TLR9 ligand was capable of enhancing the hapten-presenting ability of LCs when LC-enriched epidermal cells, but not purified LCs, were used as the LC source, suggesting that bystander keratinocytes play a role in the enhancement of LC function. Cultivation of freshly isolated epidermal cells with CpG promoted the expression of major histocompatibility complex (MHC) class II and CD86 molecules on LCs. CpG enhanced the production of interleukin (IL)-1alpha, granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumour necrosis factor (TNF)-alpha by primarily cultured keratinocytes. The addition of a cocktail of neutralizing antibodies against these cytokines abrogated the CpG-promoted, antigen-presenting ability of LC-enriched epidermal cells. Moreover, the addition of culture supernatants from CpG-stimulated keratinocytes restored the ability of purified LCs. Our study demonstrated that although the direct effect of CpG on LCs is minimal, LC function can be up-regulated indirectly by cytokines released by CpG-stimulated keratinocytes. This also implies that innate immunity evoked by TLR ligation of keratinocytes enhances acquired immunity comprising LCs and T cells.

Staphylococcal toxins in patients with psoriasis, atopic dermatitis, and erythroderma, and in healthy control subjects

BACKGROUND

The aggravating role of Staphylococcus aureus superantigens is well known in atopic dermatitis (AD) but has not yet been proven in psoriasis (PS).

OBJECTIVE

We investigated the distribution of S aureus in the skin and nares of patients with AD, PS vulgaris, erythroderma, skin infections, and sepsis, and in healthy control subjects. A Staphylococcal enterotoxin test-reversed passive latex agglutination (SET-RPLAR) test was performed to determine Staphylococcal enterotoxins A, B, C, and D.

RESULTS

S aureus was cultivated from lesional skin of 22 of 25 patients with AD and 15 of 25 patients with PS. Isolated strains were toxigenic in 44% for patients with AD and in 36% for patients with PS. The activity of disease in AD and PS according to the Severity Scoring of Atopic Dermatitis (SCORAD) or Psoriasis Area and Severity Index score, respectively, correlated significantly (P = .001) with an isolated toxigenic strain in both diseases. S aureus from skin infections was toxigenic in half of the patients. All patients with erythroderma harbored S aureus, mostly on their skin. In AD, sepsis and skin infections, toxin C and in PS toxin B was most often detected. S aureus was cultured in 12% of healthy persons. These strains were toxin negative. The limitations of these investigations are that other potentially acting enterotoxins, such as toxic shock syndrome toxin-1, which may play a role in aggravating disease, were not investigated with our latex agglutination test.

CONCLUSION

In this study, S aureus was present in more than 50% of patients with AD and PS. We found that the severity of AD and PS significantly correlated to enterotoxin production of the isolated S aureus strains.

Budesonide, but not tacrolimus, affects the immune functions of normal human keratinocytes

Topical immunosuppressant therapy is widely used in the treatment of inflammatory skin diseases such as psoriasis and atopic dermatitis. Besides its beneficial therapeutic effects, application of topical anti-inflammatory drugs may render the epidermis more vulnerable to invading pathogens by suppressing innate immune responses in keratinocytes, such as cytokine production and Toll-like receptor (TLR) expression. In order to evaluate and compare the immunosuppressive effects of different immunosuppressant drugs on keratinocytes, we treated lipopolysaccharide (LPS)-stimulated and -unstimulated normal human keratinocytes with the synthetic corticosteroid budesonide and the macrolide tacrolimus. The expressions of the pattern recognition receptors (PRRs) TLR2 and TLR4 were measured by quantitative RT-PCR, pro-inflammatory cytokines IL-1alpha, IL-8 and TNF-alpha were monitored by quantitative RT-PCR and by ELISA, and alterations in TLR2 protein level were measured by flow cytometry. Budesonide had a suppressive effect on both constitutive and LPS-induced IL-8 gene expression. The amount of TNF-alpha mRNA was diminished in unstimulated keratinocytes, while TLR2 mRNA expression was markedly enhanced both in unstimulated and LPS-treated cells after incubation with budesonide. This increase in TLR2 mRNA expression was also detectable at the protein level in LPS-stimulated cells. Tacrolimus had no effect on any of the examined genes. Budesonide, but not tacrolimus, significantly inhibited the NF-kappaB-dependent luciferase reporter activity in HaCaT cells after induction with LPS or TNF-alpha. Although tacrolimus and budesonide are both effective treatments in some inflammatory skin diseases, the data provided here imply differences in local therapeutic and adverse effects of these two topical immunosuppressants.

Establishment of murine model of allergic photocontact dermatitis to ketoprofen and characterization of pathogenic T cells

BACKGROUND

Ketoprofen is well known to evoke the allergic type of photocontact dermatitis when it is applied to the skin and irradiated with ultraviolet A (UVA) light.

OBJECTIVE

We aimed to establish a murine model of this photosensitivity and to characterize pathogenic T cells concerned with the sensitivity.

METHODS

Various strains of mice were sensitized on two consecutive days by application of ketoprofen to the shaved abdomen and irradiation of the skin with UVA. Five days later, they were elicited with ketoprofen plus UVA on the earlobes. Immune lymph node cells and epidermal cells from the challenged sites were analyzed by RT-PCR.

RESULTS

Mice were successfully sensitized and challenged with 4% and 2% ketoprofen, respective, plus UVA at 20J/cm2. The responses in H-2k mice were higher than those in the other strains examined. Immune lymph node CD4+ or CD8+ cells from ketoprofen-photosensitized H-2k mice were transferred i.v. to naïve syngeneic recipients. Mice receiving CD4+ but not CD8+ cells exhibited ketoprofen photosensitivity, but transference of both CD4+ and CD8+ cell populations was more effective. Lymph node cells from photosensitized mice expressed high levels of mRNA for Th2 cytokine (IL-4) and Th2 chemokine receptor (CCR4) as well as Th1 cytokine (IFN-gamma) and Th1 chemokine receptor (CXCR3), as assessed by RT-PCR. In addition, epidermal cells from challenged earlobes expressed increased levels of both Th1 (TARC) and Th2 (Mig) chemokines.

CONCLUSION

It is considered that not only Th1 but also Th2 cells participate in the pathogenesis of murine photocontact dermatitis to ketoprofen.

Nadifloxacin downmodulates antigen-presenting functions of epidermal Langerhans cells and keratinocytes

BACKGROUND

Nadifloxacin is an anti-microbial quinolone derivative widely used for the treatment of acne as a topical agent. This drug has been suggested to have not only anti-bacterial but also anti-inflammatory actions, which may have a beneficial effect on some aspects of inflammatory acne.

OBJECTIVE

To further clarify its abilities to modulate skin immunity, we investigated whether nadifloxacin affects the hapten- and superantigen-presenting capacities of epidermal Langerhans cells (LC) and keratinocytes, respectively.

METHODS

Immune lymph node CD4+ T cells from trinitrophenyl-sensitized BALB/c mice were cocultured with LC-enriched epidermal cells (LC-EC) that were freshly isolated from syngeneic mice and derivatized with trinitrophenyl hapten in the presence or absence of nadifloxacin. Alternatively, LC-EC were preincubated with nadifloxacin (NDFX), modified with the hapten, and cultured with immune T cells. The effects of nadifloxacin on the surface molecule expression in LC and keratinocytes were also tested by flow cytometry and cellular ELISA.

RESULTS

LC-EC cultured with nadifloxacin at 10 microg/ml or more significantly suppressed the antigen-presenting function of LC for T cells. The ability of MHC class II+ keratinocytes to present a superantigen to T cells was suppressed by preincubation of keratinocytes with 30 microg/ml or more of nadifloxacin. These functional reductions in LC and keratinocytes reflected the decreased expression of MHC class II and/or costimulatory molecules.

CONCLUSION

Nadifloxacin downmodulates cutaneous immunity by interfering with the antigen-presenting ability of epidermal cells.

Identification and antimicrobial susceptibility of micro-organisms recovered from cutaneous lesions of human American tegumentary leishmaniasis in Minas Gerais, Brazil

An evaluation of the microbiota present in cutaneous ulcers from 31 patients with a clinical and parasitological diagnosis of American tegumentary leishmaniasis (ATL) was carried out by the standard filter paper disc technique, including antimicrobial susceptibility of the bacterial isolates. Microbial examination indicated that 21 patients (67.7%) were contaminated with one to four bacteria and some of them also with yeast. A total of 142 micro-organisms were isolated. Staphylococcus aureus was the most frequently recovered bacterium (95.2% of positive patients) and was found to produce type B (70% of the staphylococcal isolates) and type C (50%) enterotoxins as well as toxic shock syndrome toxin (60%). Proteus mirabilis (33.3% of the positive patients), Streptococcus pyogenes (19.0 %), H(2)S-negative Proteus species (19.0%), Klebsiella oxytoca (14.3%), Enterobacter species (9.5%), Peptostreptococcus species (9.5%), Pseudomonas species (4.8%), Prevotella bivia (4.8%), Escherichia coli (4.8%), Streptococcus agalactiae (4.8%), Bacteroides fragilis (4.8%), Candida albicans (9.5%) and Candida tropicalis (4.8%) were also isolated. Surprisingly, Staph. aureus isolates were susceptible to almost all tested drugs, although some of them were resistant to penicillin (69%) and ampicillin + sulbactam (68%). Concerning obligate anaerobes, all the Gram-negative isolates (25% of the total) were resistant to metronidazole. The results of the present study show that microbial secondary contaminants, particularly Staph. aureus, should be considered in the diagnosis and treatment of ATL lesions.

Restricted MHC-peptide repertoire predisposes to autoimmunity

MHC molecules associated with autoimmunity possess known structural features that limit the repertoire of peptides that they can present. Such limitation gives a selective advantage to TCRs that rely on interaction with the MHC itself, rather than with the peptide residues. At the same time, negative selection is impaired because of the lack of negatively selecting peptide ligands. The combination of these factors may predispose to autoimmunity. We found that mice with an MHC class II–peptide repertoire reduced to a single complex demonstrated various autoimmune reactions. Transgenic mice bearing a TCR (MM14.4) cloned from such a mouse developed severe autoimmune dermatitis. Although MM14.4 originated from a CD4⁺ T cell, dermatitis was mediated by CD8⁺ T cells. It was established that MM14.4⁺ is a highly promiscuous TCR with dual MHC class I/MHC class II restriction. Furthermore, mice with a limited MHC–peptide repertoire selected elevated numbers of TCRs with dual MHC class I/MHC class II restriction, a likely source of autoreactivity. Our findings may help to explain the link between MHC class I responses that are involved in major autoimmune diseases and the well-established genetic linkage of these diseases with MHC class II.

Resistance to Activation-Induced Cell Death and Bystander Cytotoxicity Via the Fas/Fas Ligand Pathway Are Implicated in the Pathogenesis of Cutaneous T Cell Lymphomas

By engaging Fas, Fas ligand (FasL) on activated T lymphocytes induces activation-induced cell death (AICD), and also triggers apoptosis of target cells during immune downregulation. We previously showed that within cutaneous T cell lymphoma (CTCL) lesions, malignant CD4(+) T cells expressing FasL accumulated, and were inversely distributed with CD8(+) T cells. We thus determined the responses of human CTCL cells to AICD and their cytotoxic to Fas(+) target T cells in vitro. CTCL cells expressing Fas were resistant to AICD following activation by CD3 monoclonal antibody (mAb) whereas still undergoing apoptosis if Fas was ligated to Fas mAb. CTCL cell lines, as well as Sezary Syndrome patients' peripheral blood lymphocytes, exhibited ratio-dependent cytotoxicity to Fas(+) Jurkat cells. The kinetic study showed that FasL surface expression was absent before activation, and its expression was low and/or delayed after activation. We therefore hypothesize that CTCL cells express functional FasL possibly contributing to bystander cytotoxicity within tumor infiltrates. In addition, decreased and/or delayed FasL surface expression following activation may in part contribute to their resistance to AICD. Both bystander cytotoxicity and resistance to AICD are likely to contribute to the loss of cytotoxic anti-tumor CD8(+) T cells as well as the accumulation of malignant T cells in CTCL.

Bactericidal activity of flucloxacillin against Staphylococcus aureus in primary keratinocyte cultures of lesional and unaffected skin of patients suffering from atopic dermatitis

More than 90% of patients with atopic dermatitis (AD) are colonized by Staphylococcus aureus. Due to prevalent multi-resistant strains, it is highly difficult to eliminate S. aureus contamination of primary cell cultures of human AD skin by means of the antibiotics commonly used in cell culture. Therefore, an anti-staphylococcal treatment was investigated by which sterile proliferating keratinocyte cultures are attained from lesional and unaffected skin of AD patients by applying flucloxacillin, which in general is systemically used in vivo. The treatment with 1% flucloxacillin for 20 min included both colonized skin samples and contaminated primary cell cultures. In the case of persistent contamination, this step was repeated as often as required until complete decontamination without any cytotoxic indications was achieved. Antibacterial treatment with flucloxacillin permitted the cultivation of sterile, vital, and proliferating primary cultures of human skin keratinocytes from lesional and unaffected skin of AD patients with S. aureus colonization. The method increased the success rate of isolation of AD keratinocytes from 30 to 90%, representing on average 3 vs. 9 successfully isolated, sterile and proliferating cultures out of 10 contaminated skin biopsies, which is comparable to normal human keratinocyte isolation rates.

Presence of staphylococcal exfoliative toxin A in sera of patients with atopic dermatitis

BACKGROUND

It has been reported that the toxins that Staphylococcus aureus produces are associated with the exacerbation of atopic dermatitis (AD). It has been shown in many studies that staphylococcal enterotoxin (SE) A and SEB contribute to AD by humoral immunity through IgE production as a superantigen. On the other hand, little attention has been paid to the relationship between AD and exfoliative toxin x (ETx).

OBJECTIVE

We investigated the toxins that are frequently detected from the skin of patients and how these toxins affect AD.

METHODS

S. aureus, isolated from the skin of 100 patients with mild to severe AD, were examined for the producibility of toxins by polymerase chain reaction. Serum samples were obtained from 21 patients with mild and moderate AD. The levels of SEB, ETA, total IgE, specific IgE, and specific IgG in sera were measured by ELISA.

RESULTS

SEB was most frequently detected from S. aureus on the skin of these patients as previously reported. And ETx, to which little attention has been paid so far, was frequently detected next to SEB. Furthermore, ETA was detected from the sera of almost all the AD patients. SEB was not detected at all. Although the level of ETA in the AD group was significantly higher than that of controls, ETA-specific IgE was not detected from their sera. High levels of ETA tended to be detected from infantile patients. Although there were no significant differences in the levels of ETA-IgG between AD and the controls, its prevalence was more than twice as high as the controls in AD.

CONCLUSION

These results suggest that many AD patients were exposed to ETx. We conclude that ETx may contribute to exacerbation of AD, particularly in infants, by a mechanism that is not through specific IgE production, unlike SEB.

Paradoxical exacerbation of psoriasis in AIDS: proposed explanations including the potential roles of substance P and gram-negative bacteria

Psoriasis, a TH1-induced disorder, is not more common in human immunodeficiency virus (HIV) infection than in the general population. However, it may appear for the first time or pre-existing psoriasis may worsen and be difficult to treat in HIV disease. The paradoxical exacerbation of psoriasis in AIDS has not been fully explained. Various explanations have been proposed including (a) the reduction of Langerhans' cells (LCs) in HIV disease, (b) the direct epidermal proliferative effect of HIV, (c) the altered cytokine profile in HIV disease, (d) HIV-induced macrophage nitric oxide (NO) production, (e) the increased CD8/CD4 T-cell ratio in HIV infection and (f) the increased colonization of skin by Staphylococcus aureus. However, the observations that (a) LCs cells play an important role in the pathogenesis of psoriasis and a variety of topical and systemic psoriasis treatments cause a reversible decrease in LC function, (b) psoriasis may improve in end-stage HIV infection, (c) overproduction of some TH2 cytokines and underproduction of IL-2 in HIV infection, and (d) the presence of NO favors a TH2 response over a TH1 response make the first four explanations difficult to interpret. Since psoriasis is exacerbated in HIV infection possibly due to the increased staphylococcal colonization, and psoriatic keratinocytes could aggravate HIV infection through production of TNF-alpha, it could be reasoned that in HIV-positive psoriatics a strong vicious cycle is present between the degree of immune deficiency and the staphylococcal colonization, explaining the poor prognosis of both AIDS and psoriasis in these patients. With reference to the studies which indicate significant involvement of substance P (SP) in the pathogenesis of psoriasis and on the other hand increased release of this agent by HIV-infected immune cells it is proposed that SP plays an important role in creating the paradox. Since in HIV-positive psoriatics the source of SP is largely immune cells not neurons, capsaicin, which exerts its action selectively on a subpopulation of neurons, could not be of significant therapeutic value. As SP significantly enhances HIV-1 replication in latently infected immune cells, psoriatic lesions, being heavily infiltrated with immune cells and having high concentrations of SP, could serve as high HIV-replication foci, with the resultant rapid progression of the infection towards AIDS. Additionally, given that lipopolysaccharide is supposed to exacerbate psoriasis, increase of gram-negative infections or cutaneous colonization with these organisms in AIDS may partly explain the paradox. Understanding the HIV-induced immunodysregulation that is associated with psoriasis in some HIV-seropositive patients may assist in the delineation of the immunopathogenesis of the disease in HIV-seronegative psoriatics.

Alterations of immune functions in barrier disrupted skin by UVB irradiation

BACKGROUND

While immunologic events elicited by acute barrier disruption or UVB irradiation have been studied in detail, the biological sequel of multiple insults to the skin is not well understood.

OBJECTIVE

Since the skin would receive a variety of simultaneous stimuli in daily life, we tested the effects of sequential treatments with barrier disruption and UVB exposure on skin immunity.

METHODS

Earlobes of BALB/c mice received tape-stripping and subsequently low-dose UVB exposure. Control mice were treated with either tape-stripping or UVB. The expression of surface markers and cytokine production in Langerhans cells and keratinocytes and the elicitation response of contact hypersensitivity were compared.

RESULTS

By flow cytometry, tape-stripping augmented the expression of MHC class II, CD54, CD80, CD86 and CD40 on Langerhans cells, whereas UVB decreased the expression of some of these molecules. Combination of tape-stripping and UVB induced largely intermediate levels between these two. Upon stimulation with L cells expressing CD40L, Langerhans cells from tape-stripped and UVB-irradiated earlobes strongly transcribed mRNA for interleukin-1beta compared to each treatment. In keratinocytes, tape-stripping or UVB slightly upregulated tumor necrosis factor-alpha and interleukin-1alpha production at both mRNA and protein levels, whereas these two treatments synergistically increased the production of these cytokines. The in vitro hapten-presenting ability of Langerhans cells to trinitrophenyl-immune lymph node T cells ranked first in tape-stripping, second in tape-stripping plus UVB and third in UVB, and so did the intensity of elicitation responses in contact hypersensitivity to a hapten, picryl chloride.

CONCLUSION

It is suggested that barrier disruption and UVB antagonize with each other in contact hypersensitivity as a reflection of their effects on Langerhans cell antigen-presenting function, but they synergize in cytokine production by both Langerhans cells and keratinocytes.

Anti-allergic drug olopatadine suppresses murine contact hypersensitivity and downmodulates antigen-presenting ability of epidermal Langerhans cells

Olopatadine hydrochloride is an H1-receptor-blocker but has other anti-allergic pharmacological potencies. We investigated whether olopatadine inhibits murine contact hypersensitivity, focussing on its modulatory action on epidermal Langerhans cells serving as antigen-presenting cells. While BALB/c mice were sensitized and challenged epicutaneously with hapten, they were administered intraperitoneally with olopatadine. Olopatadine at 1 or 0.2 mg/kg of weight significantly suppressed the sensitivity when injected at least once before sensitization or challenge. In olopatadine-injected mice, the ability of Langerhans cells to present hapten to primed T cells was reduced with decreased expression of MHC class II and co-stimulatory molecules. Langerhans cells exposed in vitro to 10(-5) or 10(-6) M olopatadine had less antigen-presenting activity than control, whereas neither T cell proliferation nor keratinocyte production of IL-1alpha and IP-10 was affected at these doses. These findings suggest that olopatadine downmodulates contact hypersensitivity at least partly by interfering with the antigen-presenting ability of Langerhans cells.

Effects of staphylococci on cytokine production from human keratinocytes

BACKGROUND

Staphylococcus skin infection is characterized by the infiltration of numerous neutrophils within the epidermis; however, the precise mechanism of epidermal infiltration of neutrophils during skin infection with staphylococci is not well understood and the factors regulating the neutrophil recruitment are yet to be determined.

OBJECTIVES

We investigated the effects of staphylococci on cytokine production from keratinocytes, specifically to elucidate the mechanisms of neutrophil infiltration within the epidermis in cutaneous microbial infection.

METHODS

Cytokine production from human keratinocytes was examined after stimulation with heat-killed Staphylococcus aureus, S. epidermidis and S. intermedius.

RESULTS

Interleukin (IL)-6 and IL-8 were detected in the culture supernatants by enzyme-linked immunosorbent assay but IL-1beta, monocyte chemotactic protein-1 and tumour necrosis factor-alpha were not. IL-6 and IL-8 mRNAs were also confirmed by reverse transcription-polymerase chain reaction in the keratinocytes stimulated with killed staphylococci for 1, 3, 6, 10 and 24 h.

CONCLUSIONS

These results could explain the epidermal infiltration of neutrophils in cutaneous infection with staphylococci, suggesting that the analysis of cytokines might add valuable information for the pathogenesis of cutaneous infection with Staphylococcus species.

Flare-up reaction on murine contact hypersensitivity. III. Effect of staphylococcal enterotoxin B

Staphylococcal enterotoxin B (SEB), a bacterial superantigen, is known as an immunomodulator because it activates an extremely large number of T-cells, and induces the production of large amounts of cytokines. In this study, we examined the effects of SEB on the contact hypersensitivity reaction (CHR). BALB/c mice were first sensitized through haptens applied to the back, and CHR was then induced through challenge to the left ear using the same haptens. SEB was administered intravenously 4 weeks later, causing a flare-up, peaking at 24 h post-administration, in the left ear that had previously exhibited CHR. This flare-up reaction was hapten non-specific, and was inhibited by anti-mouse tumor necrosis factor (TNF)-alpha antibodies. The flare-up was also suppressed by the oral administration of cyclosporin A prior to the administration of SEB. These results suggest that SEB induces a flare-up of CHR via the production of TNF-alpha.

Invasion of human keratinocytes by Staphylococcus aureus and intracellular bacterial persistence represent haemolysin-independent virulence mechanisms that are followed by features of necrotic and apoptotic keratinocyte cell death

BACKGROUND

Colonization of human skin by Staphylococcus aureus is a characteristic feature of several inflammatory skin diseases, which is often followed by tissue invasion and severe cell damage. A crucial role has been attributed to staphylococcal haemolysins in the cytotoxicity to epidermal structures.

OBJECTIVES

To investigate haemolysin-independent virulence to human keratinocytes.

METHODS

The stable alpha-haemolysin, beta-haemolysin double-negative S. aureus mutant DU 5720 was compared with the fully virulent parent strain 8325-4 and with its isogenic fibronectin-binding protein A/B-negative variant DU 5883 in an invasion model.

RESULTS

This assay showed dose-dependent internalization of all the strains investigated by human HaCaT keratinocytes, with reduced internalization of DU 5883. Transmission electron microscopy revealed adhesion of staphylococci to cellular pilus-like extrusions, followed by the embedding of the bacteria in cellular grooves. Following attachment to the keratinocytes the staphylococci were engulfed into vesicles within the cytoplasm where some bacteria persisted for 24-48 h. Addition of cytochalasin D strongly reduced the bacterial uptake, suggesting an active keratinocyte process. Bacterial invasion was followed by severe keratinocyte cell damage showing the morphological changes of cytotoxic and, to a lesser extent, apoptotic cell death as determined by the trypan blue exclusion test and the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling assay. The highest levels of lethal cytotoxicity were observed in haemolysin-producing strains, whereas the induction of apoptosis seemed to depend on internalization.

CONCLUSIONS

Staphylococcal invasion of human keratinocytes represents a potent staphylococcal virulence factor, which, independently of alpha- and beta-haemolysins, leads to necrotic and apoptotic cell damage.

The keratinocyte as a target for staphylococcal bacterial toxins

Skin infections with Staphylococcus aureus are not only an important cause of morbidity and even mortality, but are thought to serve as initiation and/or persistance factors for numerous inflammatory skin diseases, including psoriasis and atopic dermatitis. One mechanism by which S. aureus can modulate the immune system is through the production of proteins such as superantigenic toxins, Protein A, as well through the cytolytic alpha-toxin. This review serves to discuss the biology of these three types of proteins, with emphasis on their ability to stimulate the production of powerful pro-inflammatory lipid- and protein-derived cytokines in keratinocytes. Characterization of interactions between these proteins and the keratinocyte can provide a better understanding of how bacterial infection modulates inflammatory skin diseases, as well as provide the basis for improved therapies involving antibacterial agents.

Expression of T-cell cytokines in challenged skin of murine allergic contact photosensitivity: low responsiveness is associated with induction of Th2 cytokines

Murine contact photosensitivity (CPS) to 3,3',4', 5-tetrachlorosalicylanilide (TCSA) is genetically controlled mainly by the major histocompatibility complex. The H-2(b,d) haplotypes are closely associated with high responders, whereas mice with H-2(k) are low or non-responders. We found that BALB/c (H-2(d)) mice were high responders in CPS not only to TCSA but also to chlorpromazine (CPZ) and benzocaine, whereas AKR/n (H-2(k)) mice were hyporesponsive to these three photoallergic agents. To elucidate the relationship between CPS responsiveness and T helper cell induction, the expression of T-cell cytokines was examined by reverse transcriptase polymerase chain reaction in the elicited skin of CPS to the three chemicals. The expression levels of interleukin(IL)-2 and interferon-gamma mRNAs were markedly higer in BALB/c mice than AKR/n mice, whereas mRNA for IL-4 was expressed strongly in AKR/n mice. These data suggest that the hyporesponsiveness of CPS to the photoallergens in AKR/n mice is closely associated with the activation/induction of Th2 cytokines at the challenged sites.

Formation of antigenic quinolone photoadducts on Langerhans cells initiates photoallergy to systemically administered quinolone in mice

Quinolone antibacterial agents are well known to cause photoallergy as a side-effect. Murine photoallergy to fluoroquinolones is a T cell-mediated immune response, evoked either by systemic fluoroquinolone and subsequent exposure of skin to ultraviolet A light or by subcutaneous injection of fluoroquinolone-photomodified epidermal cells. In this photosensitivity, epidermal Langerhans cells may be photomodified initially with the drug and thus present photohaptenic moieties to sensitize and restimulate T cells. Although we have shown that Langerhans cells photocoupled in vitro with fluoroquinolones are capable of stimulating sensitized T cells, it remains unclear whether systemically given fluoroquinolone photomodifies Langerhans cells upon ultraviolet A irradiation of the skin and the Langerhans cells become photohapten-bearing, T cell-stimulatory cells. In a murine model of fleroxacin photoallergy induced by intraperitoneal injection of the drugs plus ultraviolet A irradiation of skin, we found that Langerhans cells as well as keratinocytes are photoderivatized with fleroxacin as demonstrated with a fluoroquinolone-specific monoclonal antibody. Langerhans-cell-enriched epidermal cells prepared from mice treated with fleroxacin and ultraviolet A induced proliferation of sensitized T cells, indicating that photomodified Langerhans cells are functional. There was an optimal range of ultraviolet A dose to quantitatively and qualitatively form fleroxacin-photomodified Langerhans cells, as excess ultraviolet A rather reduced the photoantigen-presenting capacity of Langerhans cells presumably because of drug phototoxicity. Our study suggests that Langerhans cells serve as photoantigen-presenting cells in drug photoallergy.

Epidermal HLA-DR and the enhancement of cutaneous reactivity to superantigenic toxins in psoriasis

Streptococcal and staphylococcal superantigens (SAg's) have been implicated in the pathogenesis of inflammatory skin diseases, but the mechanisms by which these toxins act are unknown. The present study assessed the ability of nanogram quantities of topically applied purified toxic shock syndrome toxin-1 (TSST-1), staphylococcal enterotoxin type B, and streptococcal pyrogenic enterotoxin types A and C to induce inflammatory reactions in clinically uninvolved skin of normal controls and subjects with psoriasis, atopic dermatitis, and lichen planus. These SAg's triggered a significantly greater inflammatory skin response in psoriatics than in normal control subjects or in subjects with atopic dermatitis or lichen planus. Surprisingly, skin biopsies did not exhibit the T-cell receptor Vbeta stimulatory properties predicted for SAg-induced skin reactions. By 6 hours after patch testing with SAg's, TNF-alpha mRNA had increased in the epidermis (but not the dermis) in biopsies from psoriatics, compared with controls. Immunohistochemical studies revealed significantly higher HLA-DR expression in keratinocytes from psoriatics than from controls. However, a mutant TSST-1 protein that fails to bind HLA-DR did not elicit an inflammatory skin reaction. These results indicate that keratinocyte expression of HLA-DR enhances inflammatory skin responses to SAg's. They may also account for previous studies failing to demonstrate selective expansion of T-cell receptor Vbetas in psoriatics colonized with SAg-producing Staphylococcus aureus, and they identify a novel T cell-independent mechanism by which SAg's contribute to the pathogenesis of inflammatory skin diseases.

Possible influences of Staphylococcus aureus on atopic dermatitis-- the colonizing features and the effects of staphylococcal enterotoxins

BACKGROUND

Heavy colonization of atopic dermatitis (AD) with Staphylococcus aureus is well documented. This phenomenon suggests that S. aureus in AD lesions influences the disease processes of AD.

OBJECTIVE

We describe the importance of the presence of S. aureus and staphylococcal enterotoxins A and B (SEA, SEB) in AD lesions.

METHODS

We investigated the colonizing features of S. aureus in AD lesions using electron microscopy, the distribution of SEB in the eczematous skin of AD using immunofluorescence, the effects of SEA and SEB on normal human epidermal keratinocytes in organ culture, and the presence of specific IgE antibodies to SEA and/or SEB in serum of AD patients by enzyme immunoassay.

RESULTS

S. aureus in AD lesions colonized on and in the horny layers of the eczematous skin. SEB produced by S. aureus was distributed mainly on the dermal-infiltrated cells, especially on eosinophils. SEA and SEB stimulated expression of ICAM-1 and HLA-DR in normal human keratinocytes. More than half of the AD patients in the present study had specific IgE antibodies to SEA and/or SEB in their serum.

CONCLUSION

S. aureus and SEs have important roles in the exacerbation and prolongation of AD.

Staphylococcal toxic shock syndrome toxin-1 inhibits monocyte apoptosis

BACKGROUND

Chronic atopic dermatitis (AD) lesions are associated with colonization by exotoxin-producing Staphylococcus aureus. Evidence suggests that cytokine production in AD, particularly of GM-CSF, prolongs survival of both peripheral blood monocytes and dermal monocyte-macrophages, the predominate inflammatory cell in lesions caused by chronic AD.

OBJECTIVE

We sought to determine whether the staphylococcal exotoxin, toxic shock syndrome toxin-1 (TSST-1), could stimulate prosurvival cytokine production in monocytes and thereby inhibit apoptosis.

METHODS

Cultures of peripheral blood monocytes from normal donors and subjects with AD were incubated with various concentrations of TSST-1, and the incidence of apoptosis was assessed by examining cytospin preparations and the appearance of hypodiploid DNA in the flow cytometer. Culture supernatants were analyzed for GM-CSF, IL-1beta, and TNF-alpha by ELISA.

RESULTS

TSST-1, in a concentration-dependent manner starting at 0.1 pg/mL, significantly inhibited monocyte apoptosis and resulted in the production of the prosurvival cytokines GM-CSF, IL-1beta, and TNF-alpha. In coculture conditions with conditioned media from TSST-1-stimulated monocytes, with or without neutralizing antibody to the various cytokines, the data show GM-CSF production was responsible for the inhibition of apoptosis.

CONCLUSIONS

The data strongly suggest that staphylococcal exotoxins known to colonize skin lesions on patients with chronic AD may induce the production of GM-CSF, resulting in inhibition of monocyte-macrophage apoptosis, and thereby contribute to the chronicity of this inflammatory disease.

Clinical, microbial, and biochemical aspects of the exfoliative toxins causing staphylococcal scalded-skin syndrome

The exfoliative (epidermolytic) toxins of Staphylococcus aureus are the causative agents of the staphylococcal scalded-skin syndrome (SSSS), a blistering skin disorder that predominantly affects children. Clinical features of SSSS vary along a spectrum, ranging from a few localized blisters to generalized exfoliation covering almost the entire body. The toxins act specifically at the zona granulosa of the epidermis to produce the characteristic exfoliation, although the mechanism by which this is achieved is still poorly understood. Despite the availability of antibiotics, SSSS carries a significant mortality rate, particularly among neonates with secondary complications of epidermal loss and among adults with underlying diseases. The aim of this article is to provide a comprehensive review of the literature spanning more than a century and to cover all aspects of the disease. The epidemiology, clinical features, potential complications, risk factors, susceptibility, diagnosis, differential diagnoses, investigations currently available, treatment options, and preventive measures are all discussed in detail. Recent crystallographic data on the toxins has provided us with a clearer and more defined approach to studying the disease. Understanding their mode of action has important implications in future treatment and prevention of SSSS and other diseases, and knowledge of their specific site of action may provide a useful tool for physiologists, dermatologists, and pharmacologists.

Prevalence and role of serum IgE antibodies to the Staphylococcus aureus-derived superantigens SEA and SEB in children with atopic dermatitis

BACKGROUND

The skin of patients with atopic dermatitis exhibits a striking susceptibility to colonization and infection with Staphylococcus aureus. In this context it has been previously shown that S aureus-derived superantigens could function as classic allergens, inducing production of functionally relevant specific IgE antibodies.

OBJECTIVE

The aim of this study was to determine the prevalence and the role of circulating staphylococcal enterotoxin A (SEA)- and staphylococcal enterotoxin B (SEB)-specific IgE antibodies in children with atopic dermatitis.

METHODS

In a cross-sectional study of 58 children with atopic dermatitis, the presence of IgE antibodies to SEA and SEB was correlated with the severity of the disease and the total and other unrelated allergen-specific IgE titers and density of colonization with S aureus strains on atopic skin and episodes of superficial S aureus skin infections.

RESULTS

Twenty of 58 children (34%) were sensitized to superantigens (45% to SEB, 10% to SEA, 45% to SEA and SEB). In this group, severity of atopic dermatitis and levels of specific IgE to food and air allergens were significantly higher. The degree of disease severity correlated to a higher extent with the presence of SEA/SEB-specific antibodies than with total serum IgE levels. Density of colonization with superantigen-secreting S aureus strains was higher in the superantigen IgE-positive group. Sixty-three percent of these children experienced repeated episodes of superficialS aureus skin infections.

CONCLUSIONS

Sensitization to S aureus-derived superantigens may be involved in disease exacerbation. The presence of SEA/SEB-specific antibodies had additional explanatory value for disease severity and therefore may be helpful in the characterization of children with severe atopic dermatitis.

Role of Staphylococcus aureus surface-associated proteins in the attachment to cultured HaCaT keratinocytes in a new adhesion assay

Colonization of human skin with Staphylococcus aureus is a common feature in a variety of dermatologic diseases. In order to reproducibly investigate the adherence of Staphylococcus aureus to human epidermal cells, an in vitro assay was established using the biotin/streptavidine labeling system and the HaCaT cell line. This assay was used to define the role of several Staphylococcus aureus surface proteins with regard to their function in the staphylococcal adhesion process. Our studies included the standard laboratory strain Newman as well as its genetically constructed mutants DU5873, DU5852, DU5854, and DU5886 generated by allele replacement or transposon mutagenesis, which are deficient in the elaboration of staphylococcal protein A (spa), clumping factor (clfA), coagulase (coa), and the fibronectin-binding proteins A and B (fnbA/B), respectively. In comparison with strain Newman all mutants showed remarkably reduced adherence to the HaCaT keratinocyte cell line in our assay, yielding only between 43% and 60% of the adherence capacity of strain Newman after 60 min. Bacterial adherence could be re-established by introducing the cloned wild-type genes for the surface proteins on shuttle plasmids into the chromosomally defective mutants, thus suggesting a pathogenetic role of these proteins in the attachment of Staphylococcus aureus to human keratinocytes. Bacterial adherence was additionally enhanced by alkaline pH-values that are characteristic for skin conditions with epidermal barrier dysfunction. The use of Staphylococcus aureus mutant strains, deficient in the elaboration of defined proteins, allows specific investigation of colonization and virulence factors of this dermatologic relevant microorganism.

Roxithromycin down-modulates antigen-presenting and interleukin-1 beta-producing abilities of murine Langerhans cells

The immunomodulatory effect of the macrolide antibiotic, roxithromycin (RXM) on Langerhans cells (LC) was studied in mice. RXM inhibited the ability of LC to present superantigen and hapten to T cells at 100 microM. The superantigen-presenting activity of LC was more profoundly abrogated by RXM than the hapten-presenting activity. This functional reduction was partly attributed to an RXM-induced decrease in promotion of the expression of major histocompatibility complex class II molecules on LC. On the other hand, RXM down-modulated the production of interleukin-1 beta by LC at a lower concentration of 10 microM than concentrations that inhibited antigen presentation. These results imply that RXM exerts therapeutic effectiveness via not only bacteriocidal action but also inhibitory effect on the LC ability in T-cell-mediated cutaneous diseases that can be exacerbated by skin-colonized Staphylococcus aureus.

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.

Antigen-presenting cell function of epidermal cells activated by hapten application

Exposure to haptens initiates a series of immune and inflammatory reactions that cause migration of epidermal Langerhans cells (LC) to draining lymph nodes, antigen processing, and presentation to T cells. In the present study, the antigen-presenting cell (APC) function of epidermal cells (EC) following hapten application was determined using a cell transfer system. This function of EC in inducing contact sensitivity (CS) in the recipient mice appeared as early as 6 h after hapten painting, and reached its maximum at 24 h. The amount of hapten on EC did not correlate with the function, i.e. the amount retained on the cells was greatest immediately after hapten painting and decreased over time. Several experiments were performed to identify the cell type responsible for the APC function. Through immunomagnetic bead separation, the APC function was detected in Ia- EC, as well as in unfractionated EC from hapten-painted mice. A purified population of Ia+ cells (LC) induced CS with much less efficiency than unseparated cells. Depletion of LC by anti-Ia monoclonal antibody (mAb) and complement-mediated lysis did not impair the APC function, whereas it was reduced by the depletion of Thy-1+ cells by anti-Thy-1 mAb and complement-mediated lysis. Moreover, adherent cells that were harvested from a 48-h culture of EC obtained from hapten-painted skin, and were free of contaminating LC and gamma omega T cells, had a strong capacity to induce CS. These findings indicate that keratinocytes (KC) acquire APC function as well as LC, with hapten application. Phenotypically increased expression of intercellular adhesion molecule-1 (ICAM-1) and Thy-1 on EC was observed following hapten application, whereas expression of Ia and B7/BB1 was unaltered. The APC function of EC from hapten-painted skin was dependent on ICAM-1 and Thy-1 expression, as the mAbs for these molecules reduced the capacity to induce CS. These results suggest that hapten application induces not only LC but also KC to mature functionally and become potent APCs, and that these KC exert the APC function complementarily at local sites following the migration of LC with potent APC function to the draining lymph node.

Cross-Reactivity in Murine Fluoroquinolone Photoallergy: Exclusive Usage of TCR Vβ13 by Immune T Cells That Recognize Fluoroquinolone-Photomodified Cells

Fluoroquinolone antibacterial agents are well known to elicit photosensitivity as an adverse effect, and their cross-reactivity has been clinically documented. The photoallergenicity of fluoroquinolones is mainly derived from their photohaptenic moiety, and photomodification of skin epidermal cells with fluoroquinolones is thought to be an initial step for this photoallergy. Here we have explored, both in vivo and in vitro, T cell responses to fluoroquinolone-photomodified cells, focusing on their photoantigenic cross-reactivity. Cells were derivatized with fluoroquinolones under exposure to UV-A, and fluoroquinolone photoadducts were detected in photomodified cells by immunostaining, flow cytometry, and cell ELISA using fluoroquinolone-specific mAb. T cell-mediated hypersensitivity induced and elicited by s.c. injection of fluoroquinolone-photomodified epidermal cells was cross-reactive among six fluoroquinolones. In addition, lymph node cells from mice sensitized with fluoroquinolone-photomodified cells proliferated well in vitro not only to Langerhans cell-enriched epidermal cells photoderivatized with corresponding fluoroquinolone, but also to those photomodified with any of five other fluoroquinolones, supporting their cross-reactivity. In three fluoroquinolones tested, Th1 populations that expanded after in vitro photoantigenic stimulation of immune lymph node cells expressed the same Vβ13 of TCR. The sensitivity could be transferred by the i.v. administration of this Vβ13+ T cell line into naive recipients, in which a high percentage of Vβ13+ cells infiltrated at the challenge site. These findings suggest that these fluoroquinolones carry the same photoantigenic epitope, which is recognized by Vβ13+ T cells, leading to fluoroquinolone photosensitivity and cross-reactivity.

Follicular mucinosis associated with scarring alopecia, oligoclonal T-cell receptor V beta expansion, and Staphylococcus aureus: when does follicular mucinosis become mycosis fungoides?

A diagnosis of alopecia mucinosa, occurring as a single scalp lesion, was made in a 40-year-old white woman who had a history of trauma. Follicular mucinosis, Staphylococcus aureus, and oligoclonal expansion of the T-cell receptor V beta chain genes 6 and 7 were present in the skin. Epidermotropic T-cell skin diseases with oligoclonal T-cell proliferations may be the result of HLA- and cytokine-determined reaction patterns to persistent antigens.

Staphylococcal necrotizing fasciitis in the mammary region in childhood: a report of five cases

OBJECTIVE

Necrotizing fasciitis is a highly lethal soft tissue infection rarely reported in childhood. The initiating site is usually a local trauma or a surgical wound. We observed five cases of necrotizing fasciitis the initiating site for which was the mammary region and discuss their management.

STUDY DESIGN

We describe these five patients and review the clinical characteristics of their presentation.

RESULTS

Staphylococcal necrotizing fasciitis was observed in the mammary region in all five cases. Four children were newborn infants with a mammitis preceding the onset of necrotizing fasciitis. Surgical débridement was done only after the fourth day from onset of illness. All children were discharged in good condition after 1 month. Two have been followed until puberty, with destruction of the mammary gland in one case and good development in the other one.

CONCLUSION

Mammitis may be the initiating event for necrotizing fasciitis in neonates. Necrotizing fasciitis is a life-threatening disease; patients require early intensive care, parenteral antibiotic therapy, and surgical débridement. In a few instances surgery can be carefully delayed until the necrotic area is more delineated if the condition is diagnosed early during disease evolution and appropriate treatment is instituted in intensive care units.

Altered permeability and disordered cutaneous immunoregulatory function in mice with acute barrier disruption

In vivo and in vitro T-cell-activating ability of murine epidermal cells (EC) was investigated in acutely barrier-disrupted skin by extraction of epidermal lipids with acetone or removal of corneocytes by tape stripping. Contact sensitivity (CS) to 2,4-dinitrofluorobenzene (DNFB) and picryl chloride (PCl) and contact photosensitivity (CPS) to tetrachlorosalicylanilide (TCSA) were significantly augmented when challenged or sensitized at sites treated with acetone 24 h before, compared with the intact skin. CS to DNFB was also enhanced by tape stripping, but not by water rubbing, suggesting that physical stress or a toxic effect of acetone was not responsible for the augmentation. Semi-quantification of TCSA-EC photoadducts showed markedly increased permeability of hapten in the epidermis 24 h after acetone treatment. Bioactive IL-1alpha was more pronounced in barrier-disrupted than in intact skin. Lymph node T cells from PCl-sensitized mice proliferated significantly more in a hapten-specific and co-stimulatory molecule-dependent manner in response to trinitrophenylated (TNP) EC from acetone-treated skin than to those from untreated skin. Immunofluorescence staining of epidermal sheets and flow cytometric analysis of dispersed EC showed that subpopulations of Langerhans cells (LC) in acetone-rubbed or tape-stripped skin expressed major histocompatibility complex class II CD54 and CD86 molecules at levels higher than the rest of LC and LC from water-treated or untreated epidermis. Therefore, not only increased permeability of hapten through the epidermis but also altered immune functions of EC potentiate T-cell activation in acute barrier disruption. Such augmentation of immune reactivity may be critical to elimination of environmental noxious agents that penetrate easily into the barrier-disrupted epidermis.

Spontaneous hair follicle cycling may influence the development of murine contact photosensitivity by modulating keratinocyte cytokine production

The development of murine contact hypersensitivity is influenced by hair follicle cycling. Here, we have examined hair cycle-associated fluctuations of murine contact photosensitivity (CPS) to tetrachlorosalicylanilide (TCSA) and its immunologic mechanism(s). When the CPS outcome was monitored in correlation with their spontaneous, synchronized hair cycling, mice aged 8 and 14 weeks, with most of their hair follicles in telogen, exhibited strong CPS responses, whereas 4-, 11-, and 16-week-old mice with a predominance of anagen follicles in a large area of their integument exhibited lower responses. This suggests that the development of CPS is inhibited in mice with anagen hair follicles. Antigen-specific, T-cell receptor V beta 7+ suppressor T cells, which are recognized to down-regulate the CPS response to TCSA, were not generated in sensitized anagen mice. Culture supernatants of epidermal cells derived from mice with anagen hair follicles contained factor(s) that suppress in vivo the development of CPS. It was found that levels of mRNA for tumor necrosis factor alpha (TNF alpha) were markedly decreased in epidermal cells from early anagen to telogen mice, whereas message for IL-1 receptor antagonist (IL-1ra) was transcribed increasingly during this hair cycling. These findings suggest that altered keratinocyte production of these cytokines is involved in mediating the anagen-associated depression of CPS.

Granulocyte macrophage colony-stimulating factor is overproduced by keratinocytes in atopic dermatitis. Implications for sustained dendritic cell activation in the skin

Lesional skin of atopic dermatitis (AD) harbors high numbers of dendritic cells with enhanced stimulatory capacity for T lymphocytes. In this study, lesional AD skin was shown to stain heavily in both epidermal and dermal compartments for GM-CSF, a cytokine crucial to dendritic cell functions. Keratinocyte cultures established from uninvolved skin of AD patients exhibited markedly increased spontaneous and PMA-stimulated release of GM-CSF compared with keratinocytes from nonatopic controls. Correspondingly, keratinocytes from AD patients showed higher constitutive as well as PMA-induced GM-CSF gene expression. Larger amounts of GM-CSF were produced by AD keratinocytes, also in response to IL-1alpha, but not after stimulation with LPS, lipoteichoic acid, or staphylococcal enterotoxin B. Hydrocortisone reduced GM-CSF gene expression and protein release in both atopic and control keratinocytes. Supernatants from atopic keratinocytes were able to strongly stimulate PBMC proliferation in a GM-CSF-dependent manner. Moreover, conditioned medium from PMA-treated AD keratinocytes, together with exogenous IL-4, could support phenotypical and functional maturation of peripheral blood precursors into dendritic cells. Enhanced production of GM-CSF by keratinocytes may contribute relevantly to the establishment and chronicity of AD lesions, in particular to the increased number, sustained activation, and enhanced antigen-presenting functions of dendritic cells.