Exacerbation of atopic dermatitis on grass pollen exposure in an environmental challenge chamber.

BACKGROUND: It has frequently been speculated that pruritus and skin lesions develop after topical exposure to aeroallergens in sensitized patients with atopic dermatitis (AD). OBJECTIVE: We sought to study cutaneous reactions to grass pollen in adult patients with AD with accompanying clear IgE sensitization to grass allergen in an environmental challenge chamber using a monocenter, double-blind, placebo-controlled study design. METHODS: Subjects were challenged on 2 consecutive days with either 4000 pollen grains/m(3) of Dactylis glomerata pollen or clean air. The severity of AD was assessed at each study visit up to 5 days after challenge by (objective) scoring of AD (SCORAD). Additionally, air-exposed and non-air-exposed skin areas were each scored using local SCORAD scoring and investigator global assessments. Levels of a series of serum cytokines and chemokines were determined by using a Luminex-based immunoassay. The primary end point of the study was the change in objective SCORAD scores between prechallenge and postchallenge values. RESULTS: Exposure to grass pollen induced a significant worsening of AD. A pronounced eczema flare-up of air-exposed rather than covered skin areas occurred. In grass pollen-exposed subjects a significantly higher increase in CCL17, CCL22, and IL-4 serum levels was observed. CONCLUSIONS: This study demonstrates that controlled exposure to airborne allergens of patients with a so-called extrinsic IgE-mediated form of AD induced a worsening of cutaneous symptoms.

Staphylococcal α-toxin induces a functional upregulation of TLR-2 on human peripheral blood monocytes.

Resistance to bacterial skin infections, for example with Staphylococcus aureus (S. aureus), is based on the function of intact innate immune mechanisms. Toll-like receptor (TLR)-2 recognizes components of S. aureus and is known to be expressed on monocytes. Staphylococcal exotoxins such as staphylococcal enterotoxin B (SEB) or α-toxin are produced by many S. aureus strains. To investigate TLR-2 regulation and function on human monocytes upon stimulation with staphylococcal exotoxins to elucidate a putative feedback loop between different staphylococcal components. Monocytes were stimulated with α-toxin or SEB, respectively. TLR-2 expression and regulation as well as functional effects of TLR-2 stimulation with Pam3Cys (TLR-2/TLR-1), lipoteichoic acid (LTA) (TLR-2/TLR-6) and peptidoglycan (PGN) (TLR-2 and Nod) were then investigated both at the mRNA and protein level and compared to monocytes from patients with psoriasis. α-toxin significantly upregulated TLR-2 expression. TLR-2 mediated IL-1ß, IL-6 and IL-8 secretion was significantly augmented after upregulation with staphylococcal exotoxins. CD36 expression was significantly more downregulated after TLR-2 upregulation with SEB and consecutive LTA stimulation and TLR-2 upregulation with α-toxin following LTA and PGN stimulation, respectively. PGN enhanced CD54 expression after upregulation of the receptor with α-toxin. Expression of HLA-DR was unaffected. However, no differences were observed in monocytes from psoriasis patients compared to healthy controls. Together, our findings provide a new link between staphylococcal α-toxin and TLR-2 signalling in monocytes which may have implications for skin diseases where skin colonization with S. aureus and dysregulation of TLR-2 have been described.

Staphylococcal exotoxins induce interleukin 22 in human th22 cells.

BACKGROUND: We have shown previously that T cells from atopic dermatitis (AD) patients produce more IL-22 upon staphylococcal exotoxin stimulation compared to psoriasis patients and healthy controls. The role of staphylococcal exotoxins on polarized memory T helper (Th)22 cells which are enriched in inflamed AD skin remains elusive. Our aim was to investigate IL-22 production in response to staphylococcal enterotoxin B (SEB) and α-toxin stimulation in human memory T cells and polarized Th22 cells. METHODS: IL-22 induction was investigated in human peripheral blood-derived CD4+CD45RO+CD45RA- T cells and polarized Th22 cells after SEB and sublytic α-toxin stimulation in a time-dependent manner at the mRNA and protein (ELISA) levels. RESULTS: Th22 cells secreted more IL-22 compared to freshly isolated peripheral blood-derived memory T cells. SEB and α-toxin induced IL-22 in memory T cells as well as in Th22 cells. More IL-22 was induced by SEB and α-toxin in freshly isolated peripheral blood memory T cells compared to Th22 cells derived from memory T cells in long-term cell culture without polarization and Th22 cells under Th22-promoting conditions with IL-6 and TNF-α. No differences in IL-22 induction by staphylococcal exotoxins were observed between cells from AD compared to psoriasis patients and healthy controls. CONCLUSIONS: Increased IL-22 secretion can promptly be induced by staphylococcal exotoxins in skin infiltrating CD4+CD45RO+CD45RA- memory T cells and can potentially amplify chronic skin inflammation in AD in the context of bacterial colonization and infection. This should be investigated further in detail in lesional skin of AD and psoriasis patients.

Is there a therapeutic benefit of complete lymph node dissection in melanoma patients with low tumor burden in the sentinel node?

In the case of a positive sentinel lymph node (SLN), melanoma patients are recommended to proceed to complete lymph node dissection (CLND). However, CLND for SLN-positive patients - especially with minimal tumor burden in SLN - is becoming more controversial. We analyzed the clinical course of 305 SLN-positive patients with a mean follow-up of 51.1 months by Kaplan-Meier analyses. Overall, 58/305 (17%) patients did not undergo CLND. These were compared with a matched selection of 58 comparable patients who underwent CLND. Moreover, 106/305 patients with minimal tumor burden in SLN (<0.1 mm diameter of the largest tumor deposit) were analyzed separately. Of these 106 patients, 34 did not undergo CLND, whereas 72/106 patients were treated by CLND. In the matched groups, the CLND group and the non-CLND group did not differ significantly with respect to clinical characteristics, characteristics of the primary melanoma, and histopathological parameters of SLN. There were no differences in recurrence-free survival (P=0.765) and overall survival (P=0.844). The total number of regional lymph node metastases and time to regional lymph node metastases were not significantly higher for non-CLND patients. The subgroup of patients with minimal tumor burden in SLN also did not benefit significantly from CLND. In our analyses from a single German center, we could not find any evidence for a therapeutic survival benefit for CLND after positive SLN. However, future prospective randomized trials should confirm these data.

microRNA-21 is upregulated in malignant melanoma and influences apoptosis of melanocytic cells.

Overexpression of microRNA-21 (miR-21) has been observed in various cancer types, but little is known about the role of miR-21 in melanoma. In this study, we demonstrate that levels of miR-21 are significantly increased in primary melanoma tissues as compared to benign nevi and in human melanoma cell lines as compared to melanocytic cell preparations. We show that downregulation of miR-21 in melanoma cell lines with high endogenous miR-21 expression induced apoptosis, whereas proliferation was not significantly altered. Upregulation of miR-21 in melanocytes resulted in increased proliferation and decreased apoptosis. However, in the MEWO melanoma cells with low endogenous miR-21 expression, upregulation of miR-21 had no functional effects. These findings indicate a potential pathogenetic role of miR-21 upregulation in a subgroup of melanomas.

Participation of complement 3a receptor (C3aR) in the sensitization phase of Th2 mediated allergic contact dermatitis.

The complement system has emerged as a bridge between innate and adaptive immune responses. An involvement of C3aR has been described during skin inflammation. The aim of the study was to investigate the role of C3a in a mouse model of allergic skin inflammation, such as allergic contact dermatitis (ACD) which is a clinical manifestation of contact sensitivity (CS). The sensitization phase was studied using the local lymph node test: Mice were sensitized on three consecutive days by application of non-irritant concentrations of toluene-2,4-diisocyanate (TDI; 0.5%) onto the ear skin. On day 5, auricular draining lymph nodes were obtained. The elicitation phase was investigated by sensitization with TDI on the depilated and tape-stripped abdominal skin and challenge with TDI on the ear skin and measuring of ear swelling in vivo and cytokine secretion in activated splenocytes in vitro respectively. Complement 3a receptor deficient (C3aRKO) mice showed increased cytokine responses (interleukin[IL]-5, IL-6, IL-17, granulocyte macrophage-colony stimulating factor [GM-CSF]) in the sensitization phase of ACD to TDI. However, no differences in CS responses to TDI were observed in C3aR KO mice compared with WT controls in the elicitation phase of ACD as assessed by measuring of ear swelling in vivo and cytokines in skin and in activated splenocytes in vitro, namely IL-1α, IL-2, IL-4, IL-5, IL-6, IL-10, IL-17, interferon-γ (IFN-γ), GM-CSF and tumor necrosis factor (TNF)-α. These findings provide a new insight into the participation of C3a in the sensitization phase of CS immune responses.

Staphylococcal α-toxin induces a higher T cell proliferation and interleukin-31 in atopic dermatitis.

BACKGROUND: Patients with atopic dermatitis (AD) are frequently colonized with α-toxin-producing Staphylococcus aureus which is in turn positively correlated with the severity of eczema. METHODS: IN this study we addressed T cell proliferation and T cell as well as monocyte cytokine secretion upon α-toxin stimulation in peripheral blood mononuclear cells (PBMCs) from AD patients compared to healthy controls. RESULTS: We found that α-toxin stimulation of PBMCs markedly enhanced T cell proliferation both in patients with AD and healthy controls and was significantly increased in AD patients compared to healthy controls. PBMCs of AD patients secreted significantly more IL-31 compared to those of healthy controls upon α-toxin and SEB stimulation. Moreover, α-toxin stimulation yielded an increase in T cell (IL-2, IL-9, IL-10 and IFN-γ) as well as monocyte (IL-1ß and TNF-α) cytokine secretion. CONCLUSION: Our results could partly explain how skin colonization and infection with S. aureus can contribute to chronic skin inflammation and pruritus in AD.

A protective role of complement component 3 in T cell-mediated skin inflammation.

Keratinocytes synthesize complement component 3 (C3) constitutively, and increased expression of C3 has been described during skin inflammation. In this study, we investigated the role of C3 in T cell-mediated allergic contact dermatitis, which is a clinical manifestation of contact sensitivity (CS). C3-deficient mice (C3KO) showed substantial higher CS responses to haptens, inducing a Th1 cytokine-mediated skin inflammation (2,4-dinitrofluorobenzene and dinitrochlorobenzene), and to haptens known to induce a Th2-polarized inflammatory response (fluoro-isothiocynate and toluene-2,4-diisocyanate) as compared to their wild-type (WT) controls. There was a higher influx of GR-1(+) , CD4(+) , and CD8(+) cells into the skin of hapten-treated C3KO mice compared with WT mice. Activated splenocytes from C3KO mice immunized with DNCB secreted higher amounts of IFN-γ compared with WT controls but not of Th2 (IL-4, IL-5, and IL-10) cytokines or IL-17. A higher secretion of IL-12 from splenocytes of C3KO mice as compared with WT mice was observed after TLR-4 ligand (LPS) or TLR-2 ligand (peptidoglycan) stimulation. Thus, an increased expression of IL-12 and of IFN-γ may be responsible for the increased hapten-induced inflammation in C3 deficiency. Finally, we demonstrated that C3KO mice developed oral tolerance to haptens to a lower degree than WT mice. Our findings provide a new insight into a novel anti-inflammatory role of C3 in skin inflammation.

Malassezia sympodialis thioredoxin-specific T cells are highly cross-reactive to human thioredoxin in atopic dermatitis.

BACKGROUND: IgE-mediated cross-reactivity between fungal antigens and human proteins has been described in patients with atopic dermatitis (AD), but it remains to be elucidated whether there is also cross-reactivity at the T-cell level. OBJECTIVE: We sought to explore cross-reactivity at the T-cell level between the fungal thioredoxin (Mala s 13) of the skin-colonizing yeast Malassezia sympodialis and its homologous human thioredoxin (hTrx). METHODS: T-cell lines (TCLs) were generated in the presence of rMala s 13 from the peripheral blood and from skin biopsy specimens of positive patch test reactions of patients with AD sensitized to Mala s 13 and hTrx. Patients with AD not sensitized to Malassezia species, healthy subjects, and patients with psoriasis served as control subjects. Mala s 13-specific T-cell clones (TCCs) were generated from TCLs. TCCs were characterized by antigen specificity, phenotype, and cytokine secretion pattern. Human keratinocytes were stimulated with IFN-γ, TNF-α, and IL-4, and the release of hTrx was determined by means of ELISA. RESULTS: Mala s 13-specific TCLs and TCCs from the blood and skin of patients with AD sensitized to Mala s 13 and hTrx were fully cross-reactive with hTrx. Mala s 13- and hTrx-specific TCCs could not be generated from control subjects. The majority of cross-reactive TCCs were CD4(+) and coexpressed cutaneous lymphocyte antigen. In addition to T(H)1 and T(H)2 TCCs, we could also identify TCCs secreting IL-17 and IL-22. After stimulation with IFN-γ and TNF-α, keratinocytes released substantial amounts of thioredoxin. CONCLUSION: In patients with AD sensitized to Malassezia species, cross-reactivity at the T-cell level to Mala s 13 and the homologous hTrx is detectable. hTrx autoreactive skin-homing T cells might be relevant for cutaneous inflammation in patients with AD.

Intrinsic alterations of pro-inflammatory mediators in unstimulated and TLR-2 stimulated keratinocytes from atopic dermatitis patients.

In many patients with atopic dermatitis (AD), the disease is complicated by their enhanced susceptibility to bacterial skin infections, especially with Staphylococcus aureus (S. aureus). Resistance to bacterial skin infections, e.g. S. aureus, is based on the function of intact innate immune mechanisms in the epidermis, mainly provided by keratinocytes. Toll-like receptor (TLR)-2 recognizes components of S. aureus and is known to be expressed on keratinocytes. The aim of this study was to investigate intrinsic TLR-2 expression and cytokine secretion upon TLR-2 stimulation with peptidoglycan (PGN), lipoteichoic acid (LTA) and N-palmitoyl-S-[2,3-bis(palmitoyl)-(2RS)-propyl]-(R)cysteinyl-alanyl-glycine (Pam3Cys) in keratinocytes from patients with AD compared to healthy controls. Human primary keratinocytes (HPKs) were cultivated from hair follicles of patients with AD and non-atopic healthy controls and stimulated with Pam3Cys, LTA and PGN. TLR-2, TLR-1 and TLR-6 expression were investigated at the mRNA level. IL-6, IL-8, chemokine C-C motif ligand (CCL)-20 and MMP-9 production were studied at the protein level. TLR-2, TLR-1 and TLR-6 were expressed on both HPKs from patients with AD as well as healthy controls without significant differences between these groups. HPKs from patients with AD had an intrinsically reduced capacity to produce IL-6, IL-8, CCL-20 and MMP-9 and responded less to TLR-2 stimulation compared to HPKs from healthy controls. Our findings show evidence for intrinsic alterations in HPKs from patients with AD compared to healthy controls and diminished responses upon TLR-2 stimulation that might contribute to the enhanced susceptibility to skin infections with S. aureus.

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

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

TLR-2-mediated cytokine and chemokine secretion in human keratinocytes.

The human epidermis provides a first line of defense against exogenous pathogens. Resistance to bacterial skin infections, e.g. with Staphylococcus aureus (S. aureus), is based on the function of intact innate immune mechanisms in the epidermis, mainly provided by keratinocytes. They establish the local cytokine and chemokine milieu which is necessary for attracting other cells participating in an immune response. Toll-like receptor (TLR)-2 recognizes components of S. aureus and is known to be expressed on keratinocytes. The aim of this study was to investigate TLR-2-mediated chemokine and cytokine secretion on human primary keratinocytes (HPKs) both on mRNA and on protein level. As there is no selective TLR-2 ligand known so far, we chose Pam3Cys that acts via TLR-2/TLR-1 heterodimers, lipoteichoic acid (LTA) that acts via TLR-2/TLR-6 and peptidoglycan (PGN) which acts via TLR-2 and Nod. Pam3Cys stimulation yielded in an enhanced secretion of CCL20, CCL2, MMP9 and IL-8 in HPK, whereas stimulation with PGN or LTA showed no or solely slight effects. Our findings show evidence for a functional TLR-2/TLR-1 signalling profile in HPKs upon stimulation with Pam3Cys contributing to the defense against bacterial skin infections.

Staphylococcal exotoxins are strong inducers of IL-22: A potential role in atopic dermatitis.

BACKGROUND: Patients with atopic dermatitis (AD) and psoriasis are frequently colonized with Staphylococcus aureus that produces staphylococcal enterotoxin B (SEB) and α-toxin. In patients with AD, S aureus colonization is positively correlated with the severity of their eczema. Moreover, IL-22-producing cells have been shown to accumulate in AD skin and to correlate with disease severity. OBJECTIVE: To assess IL-22 production in response to SEB and sublytic α-toxin stimulation in patients with AD and psoriasis compared with healthy controls. METHODS: IL-22 induction was investigated in PBMCs, T cells, and autologous cocultures of keratinocytes and T cells on SEB and α-toxin stimulation in a time-dependent and dose-dependent manner at the mRNA and protein (ELISA and flow cytometry) level. Anti-IL-1 receptor or anti-IL-6 antibodies were used in blocking experiments. RESULTS: Staphylococcal enterotoxin B and sublytic α-toxin concentrations induced IL-22 production in PBMCs and isolated CD4(+) T cells. IL-22 secretion was enhanced by α-toxin stimulation in autologous cocultures of keratinocytes and T cells. In T cells and PBMCs from patients with AD, IL-22 secretion was significantly enhanced on α-toxin stimulation compared with patients with psoriasis and healthy controls. CONCLUSION: Increased IL-22 secretion induced by staphylococcal exotoxins in the skin partially explains how skin colonization and infection with S aureus can contribute to chronic skin inflammation in AD.

Innate immunity, allergy and atopic dermatitis.

PURPOSE OF REVIEW: We review here the recent discoveries in innate immunity that shed light on the pathophysiology of atopic dermatitis. RECENT FINDINGS: The mechanisms that promote the enhanced susceptibility to cutaneous infections in atopic dermatitis are complex interactions among several factors. They include skin barrier dysfunction, reduced skin lipid content, and abnormalities of the innate immune response. Some of the innate immune defects observed in atopic dermatitis are primary defects, such as epithelial barrier defects and defects in signaling or expression of innate receptors. Others may be secondary to the effects of the adaptive immune response. For example, deficiencies in antimicrobial peptides may be due to the overexpression of T helper 2 cytokines such as interleukin-4 and interleukin-13. However, how all components interact with each other remains to be fully investigated. SUMMARY: To break this vicious circle, a multiprolonged approach directed at healing or protecting the skin barrier and addressing the immune dysregulation is necessary to improve and control the disease.

Dysregulation of CD36 upon TLR-2 stimulation in monocytes from patients with atopic dermatitis and the TLR2 R753Q polymorphism.

BACKGROUND: The cutaneous colonization with Staphylococcus aureus represents a potent trigger factor of atopic dermatitis. Toll-like receptor (TLR)-2 and CD36 have been shown to play a pivotal role in the internalization of staphylococcal components. AIMS: To investigate the impact of TLR-2 ligands on cell surface protein expression in monocytes from wild type (WT) AD patients and TLR-2 R753Q polymorph AD patients. RESULTS: CD36 expression was significantly less downregulated in TLR-2 polymorph AD patients compared to wild type AD patients upon stimulation with peptidoglycan (PGN) and lipoteichoic acid (LTA) and compared to healthy controls upon stimulation with PGN. Expression of CD86 was higher upon N-palmitoyl-S-[2,3-bis(palmitoyl)-(2RS)-propyl]-(R)cysteinyl-alanyl-glycine (Pam3Cys) stimulation in TLR-2 R753Q polymorph AD patients compared to wild type AD patients. Expression of CD80 and CD54 were unaffected. CONCLUSION: The differences in CD36 expression in TLR-2 polymorph AD patients compared to wild type AD patients and healthy controls may be associated with an enhanced susceptibility to skin infections with S. aureus.

Quantitative patch and repeated open application testing in hydroxyisohexyl 3-cyclohexene carboxaldehyde sensitive-patients.

OBJECTIVE: To identify the concentration of the fragrance compound hydroxyisohexyl 3-cyclohexene carboxaldehyde (INCI) (HICC) that is sufficiently low not to cause an allergic reaction in patients with proven sensitization. METHODS: Repeated open application testing (ROAT) in 64 subjects with 2 preparations (perfume and cream) in different concentration (0.005-2.5%). Confirmatory patch testing with four preparations in two different concentrations (2.5% and 5%). RESULTS: The concentrations of HICC being tolerated by 90% of those sensitized to HICC are estimated as <88.2 ppm (cream) and <270 ppm (perfume) equivalent to 1.2 microg/cm(2) (perfume) and 4.9 microg/cm(2) (cream). Patch test preparations differed with regard to sensitivity (88.5-98.1%) and specificity (37.5-87.5%) against the ROAT result as external criterion. ROAT concentrations and the reaction strength in patch testing were inversely correlated (Kendall's tau-b: 0.69), both indicating the existence of different degrees of susceptibility. CONCLUSION: To protect 90% (50%) of people sensitized, the use concentration should be in the range of 0.009-0.027% (0.18-0.34%), depending on the product type. Taking into account these results, excessive concentrations should be avoided, as this would continue to sensitize people. Close monitoring is indispensable to prove the efficacy of any recommendations aiming to prevent induction.

Intracutaneous injection of the macrophage-activating lipopeptide-2 (MALP-2) which accelerates wound healing in mice--a phase I trial in 12 patients.

Chronic skin ulcers, such as leg ulcers, pressure sores and diabetic foot ulcers, are a challenge to physicians and medical personnel and a cause of tremendous discomfort and ensuing loss of quality of life to the patients. Wound healing involves production and action of various growth factors. A novel approach, distinct from the application of single growth factors, is the administration of the macrophage stimulator macrophage-activating lipopeptide-2 (MALP-2). The rationale is based on the finding that macrophages are the main source of several growth factors required for wound healing, which are sequentially released during this process. MALP-2 has previously been shown to be effective in an established animal model with diabetic mice. The purpose of the present phase I study was to establish tolerability of MALP-2 when applied into small cutaneous wounds in human beings. Twelve patients (six females and six males; mean age 66.8 years; range 52-87 years) with different diagnoses were enrolled into the study. An artificial wound was created with a 2-mm diameter skin biopsy punch and a volume of 30 microl MALP-2 (0.125-1 microg) or vehicle control, respectively, was injected intracutaneously into the wound and closed with a water-resistant transparent adhesive. Photos were taken daily from every patient up to 6 days, and skin biopsies were performed after 1 week from six patients. We could show in the present study for the first time that MALP-2 caused a transient erythema and was tolerated without any systemic side effects up to a dose of 1 microg per wound in human beings. In healthy as well as in diabetic patients, MALP-2 induced local inflammation that faded after 48 h. The effectiveness of MALP-2 in the healing of chronic wounds in humans, e.g. in chronic skin ulcers, such as leg ulcers, pressure sores and diabetic foot ulcers, could now be addressed in further studies.

Antibiotic treatment of cutaneous infections with Staphylococcus aureus in patients with atopic dermatitis: current antimicrobial resistances and susceptibilities.

BACKGROUND/AIMS: Atopic dermatitis (AD) is a common chronic inflammatory skin disease. In many patients, the disease is complicated by enhanced susceptibility to skin infections, especially with Staphylococcus aureus. The aim of this study was to determine the antimicrobial susceptibility of skin-colonizing S. aureus strains in patients with AD and consecutively to recommend the first-line antibiotic therapy. METHODS: We studied S. aureus-positive skin swabs (n = 102) from lesional skin of children, adolescents and adults with AD presenting to our inpatient and outpatient departments from January 2005 to June 2006. RESULTS: Antimicrobial susceptibility testing revealed resistance against oxacillin, amoxicillin/clavulanic acid, cephalexin and cefuroxim in 3%, against tetracycline in 17%, against gentamicin in 16%, against erythromycin and clindamycin in 21%, against trimethoprim/sulfamethoxazol in 23%, against levofloxacin in 23%, against fusidic acid in 25%, against fosfomycin in 12% and against rifampicin in 16%. All strains isolated were susceptible to vancomycin. CONCLUSION: Currently, the first generation cephalosporin cephalexin appears to be the preferential first-line antibiotic for the treatment of bacterial superinfections with S. aureus in children and adults with AD due to its restricted antimicrobial spectrum to Gram-positive bacteria and a limited number of Gram-negative strains. Cefuroxim and amoxicillin/clavulanate, which also showed 3% resistances in our patients, cover a broader range of bacterial micro-organisms. However, a broader coverage is not required in case of AD, as S. aureus is the most frequent bacterial micro-organism causing skin infections.

The Toll-like receptor 2 R753Q mutation modifies cytokine production and Toll-like receptor expression in atopic dermatitis.

BACKGROUND: Impaired host defense mechanisms may crucially modulate the pathogenesis of atopic dermatitis (AD). More than 10% of patients with AD are heterozygous for the Toll-like receptor 2 (TLR-2) R753Q single nucleotide polymorphism (SNP) and exhibit severe eczema. OBJECTIVE: To elucidate the functional effect of the TLR-2 mutation and its putative relevance for AD. METHODS: Using the human embryonic kidney 293 transfection system, we characterized the properties of the TLR-2 R753Q SNP. Moreover, TLR-2 expression, IL-8 production, and cytokine secretion were analyzed in monocytes and CD4+ T cells of patients with AD with and without the mutant TLR-2 gene. RESULTS: Human embryonic kidney 293 transfectants mimicking this heterozygous mutation produced less IL-8 when stimulated with lipoteichoic acid (LTA), heat-inactivated Staphylococcus aureus or triacylated lipopeptides requiring the TLR-2/1 heterodimer. Suppressed production of IL-8 was confirmed in monocytes from patients with mutant AD after stimulation with peptidoglycan. Cell surface TLR-2 expression was severely impaired in CD3/CD28 activated CD4+ T cells of patients with AD bearing the mutant receptor, which could be restored on LTA stimulation. In contrast, LTA decreased TLR-2 expression among nonatopic individuals and patients with AD with the TLR-2 wild-type gene. T cells from patients with AD exhibited markedly suppressed IL-2 production after macrophage-activating lipopeptide-2 activation. However, no difference was found between mutant and wild-type patients with AD for IL-5, TNF-alpha, IFN-gamma, and IL-2 production. CONCLUSION: Collectively, the outcome of innate and adaptive immune responses in AD is modulated by the TLR-2 R753Q SNP.