Margarete Niebuhr

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.

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.

Interleukin (IL)-31 induces pro-inflammatory cytokines in human monocytes and macrophages following stimulation with staphylococcal exotoxins

To cite this article: Kasraie S, Niebuhr M, Werfel T. Interleukin (IL)‐31 induces pro‐inflammatory cytokines in human monocytes and macrophages following stimulation with staphylococcal exotoxins. Allergy 2010; 65: 712–721.

Dysregulation of toll‐like receptor‐2 (TLR‐2)‐induced effects in monocytes from patients with atopic dermatitis: impact of the TLR‐2 R753Q polymorphism

Background:  Atopic dermatitis (AD) is often complicated by an enhanced susceptibility to bacterial skin infections, especially with Staphylococcus aureus. Toll‐like receptors (TLR), especially TLR‐2 recognizes cell wall components of S. aureus, e.g. lipoteichoic acid (LTA) and peptidoglycan (PGN). A heterozygous TLR‐2 R753Q polymorphism occurs in a frequency of 11.5% in adult AD patients and has been shown to be associated with a severe phenotype of AD.

Staphylococcal Alpha-Toxin Is a Strong Inducer of Interleukin-17 in Humans

ABSTRACT 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.

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.

Impaired TLR-2 expression and TLR-2-mediated cytokine secretion in macrophages from patients with atopic dermatitis

Background:  In many patients with atopic dermatitis (AD), the disease is complicated by their enhanced susceptibility to bacterial skin infections, especially with Staphylococcus aureus. The pattern recognition receptor toll‐like receptor (TLR)‐2 recognizes components of S. aureus, for example, lipoteichoic acid (LTA) and peptidoglycan (PGN) and, therefore, might be crucial in the pathogenesis and flare‐ups of AD.

Innate immunity, allergy and atopic dermatitis.

Purpose of reviewWe review here the recent discoveries in innate immunity that shed light on the pathophysiology of atopic dermatitis. Recent findingsThe 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. SummaryTo 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.

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.

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.