Peptide specificity and HLA restriction do not dictate lymphokine production by allergen-specific T-lymphocyte clones.

Human and murine CD4+ T lymphocytes can be subdivided into distinct subsets [T-helper type 0 (Th0), Th1 or Th2], based on their lymphokine production profiles. Not much is known about the factors that determine these restricted lymphokine secretion profiles. Peptide specificity and human leucocyte antigen (HLA) restriction may be such factors. As it is well established that allergen-specific T lymphocytes from atopic individuals and non-atopic controls differ in their lymphokine secretion profile, we studied two allergen-specific T-lymphocyte clones (TLC) with identical peptide specificity and HLA restriction that were generated from the peripheral blood of an atopic donor and a non-atopic control donor. The two CD4+ TLC recognize the same epitope (20-33) of the house dust mite Dermatophagoides pteronyssinus major allergen Der p II. Both TLC recognize the epitope in an HLA-DQB1*0602-restricted manner. However, the lymphokine production profiles of these TLC show clear differences after allergen-specific or polyclonal activation. As expected, TLC JBD4 from the atopic donor produced high levels of interleukin-4 (IL-4) without detectable interferon-gamma (IFN-gamma), whereas TLC PBA1 from the non-atopic donor produced both IFN-gamma and IL-4 upon allergen-specific or polyclonal activation. Inasmuch as both TLC recognized the same epitope of Der p II in association with the same HLA-DQ molecule, these data suggest that peptide specificity and HLA restriction of human allergen-specific TLC do not dictate their lymphokine secretion profile.     

In vivo relevance of CD30 in atopic dermatitis

CD30 expression was evaluated by immunohistochemistry in lesional skin biopsies of eight patients with active atopic dermatitis (AD) and three patients with allergic contact (nickel-induced) dermatitis (ACD). CD30 expression was also assessed in a large panel of CD4 + and CDS + T-cell clones generated from the skin biopsies of four patients with AD. Finally, the levels of soluble CD30 (sCD30) were measured in the serum of 41 patients with AD, 19 patients with ACD, and 60 healthy controls. In all specimens of lesional AD skin, where the great majority of infiltrating cells were CD4+ T cells, remarkable numbers of cells were CD30+, whereas virtually no CD30 + cells were found in the skin of patients with ACD. In CD4+ T-cell clones generated from the lesional AD skin, most of which produced both interleukin (IL)-4 and interferon-gamma (IFN-γ) (Th0–like cells) or IL-4 and 1L-5, but not IFN-γ (Th2–like cells), CD30 expression directly correlated with the ability to produce IL-4 and IL-5, but was inversely related to IFN-γ production. High levels of sCD30 (correlated with disease activity: r = 0.618) were detected in the serum of most AD patients, whereas there was no increase of sCD30 levels in the serum of patients with ACD. These data support the view that Th0/Th2–type responses predominate in the skin of patients with AD and suggest that the presence of CD30 + T cells in tissues and/or increased levels of sCD30 in biologic fluids are indicative of Th2–dominated responses.     

Skin-derived aeroallergen-specific T-cell clones of Th2 phenotype in patients with atopic dermatitis.

T-cell lines have been derived from aeroallergen-induced eczematous patch test sites of patients with atopic dermatitis (AD). Biopsy specimens were obtained 24 hours after allergen application to the skin, and only in vivo-activated T cells were propagated. From one patient, the T-cell lines were subcloned at 0.3 cells per well. With allergen-induced interleukin (IL) production, all clones tested (n = 13) were found to be specific for the allergen, producing IL-4 and granulocyte-macrophage-colony-stimulating factor. No IL-2 or interferon-gamma was found. The allergen-specific proliferative response of these clones, although the response was dependent on exogenous IL-2 or IL-4, also proved that all clones were allergen specific. Under optimal stimulation (aCD3 plus phorbol myristate acetate), 15% of the clones appeared to be of Th0 phenotype and 70% of Th2 phenotype. In 15% of the clones, IL-4 was produced in the absence of IL-2, IL-5, or interferon-gamma. Supernatants of all clones tested induced IgE production by B cells from normal non-atopic donors. The T-cell lines of the other patient demonstrated similar results; allergen-specific proliferation was dependent on exogenous IL-2 or IL-4 and stimulation with aCD3 plus phorbol myristate acetate demonstrated that the T cells in these lines were of the Th2 phenotype. In conclusion, our data reveal that, in AD, percutaneous sensitization to aeroallergens may occur and indicate that allergen-specific Th2 type T cells may be responsible for the high levels of (specific) IgE found in 80% of patients with AD.     

Positive atopy patch test reactions to Pityrosporumorbiculare in atopic dermatitis patients

BACKGROUND: Pityrosporum orbiculare, although a part of our normal cutaneous microflora, can cause skin infections and induce specific immunoglobulin (Ig) E antibodies in atopic dermatitis patients. P. orbiculare is therefore considered to be one of the trigger factors for atopic dermatitis. OBJECTIVE: To investigate if P. orbiculare can induce an eczematous reaction in atopic dermatitis patients, seborrhoeic dermatitis patients and healthy controls. METHODS: Fifteen atopic dermatitis patients, eight seborrhoeic dermatitis patients and eight healthy controls were patch tested with extract of P. orbiculare on non-lesional, tape-stripped skin of the back. NaCl was used as a negative control. The patch tests were evaluated after 24, 48 and 72 h. Skin biopsies were taken from P. orbiculare patch test sites at 24 h and 72 h, from NaCl patch test sites at 72 h, from non-lesional skin and, in the atopic dermatitis patients, also from lesional skin. The skin biopsies were investigated with immunohistochemical techniques. P. orbiculare-specific IgE in serum was analysed with RAST. RESULTS: Specific IgE to P. orbiculare was found in serum from 13/15 atopic dermatitis patients and in eight of them a positive patch test reaction to P. orbiculare was observed, with a maximal reaction at 48 h. Significantly higher serum levels of P. orbiculare-specific IgE were detected in patch test-positive compared with patch test-negative atopic dermatitis patients (P < 0. 01). The seborrhoeic dermatitis patients and healthy controls were RAST and patch test-negative for P. orbiculare. In the patch test-positive atopic dermatitis patients an infiltration of CD4+ T cells and eosinophils was observed at the P. orbiculare patch test sites together with an upregulation of ICAM-1 and HLA-DR expression. CONCLUSIONS: P. orbiculare can induce an eczematous reaction in sensitized atopic dermatitis patients and may be an important trigger factor in these patients. The P. orbiculare patch test can be of diagnostic value in this subgroup of atopic dermatitis patients.     

Lipoteichoic acid from Staphylococcus aureus enhances allergen-specific immunoglobulin E production in mice

BACKGROUND: Our previous study demonstrated that lipoteichoic acid (LTA) from Staphylococcus aureus induced T helper type 2 (Th2)-prone dermatitis resembling that seen in atopic dermatitis (AD) patients in mice sensitized percutaneously with an allergen. However, the effects of LTA on allergen-specific IgE production in such sensitized mice have not been elucidated. OBJECTIVE: The purpose of this study was to determine the effects of LTA from S. aureus on allergen-specific IgE production in mice sensitized percutaneously with a house dust mite antigen (MA). METHODS: Mice were sensitized with a single topical application of MA and/or LTA to barrier-disrupted abdominal skin. One to 5 weeks later, MA-specific IgE antibodies in sera from sensitized mice were detected by an enzyme-linked immunosorbent assay (ELISA). Expression of B7.1 (CD80), B7.2 (CD86) and CD40L molecules by CD40-positive (CD40+) and CD4-positive (CD4+) cells in the lymph nodes of sensitized mice were analysed by flow-cytometry (FACS). RESULTS: Simultaneous sensitization with MA and LTA increased IgE production 3 weeks later, significantly more than sensitization with MA alone. FACS analysis of CD40+ cells in the lymph nodes from sensitized mice showed that simultaneous sensitization with MA and LTA did not enhance CD80- or CD86-expression by antigen-presenting cells such as B lymphocytes and dendritic cells more than sensitization with MA alone. However, analysis of CD4+ cells in the lymph nodes showed that simultaneous sensitization with MA and LTA increased the number of CD40L-expressing Th cells more than sensitization with MA alone. CONCLUSION: These results suggest that LTA enhances allergen-specific IgE production by a mechanism associated with up-regulation of CD40L-expressing Th cells and this might explain the role of skin colonization with S. aureus in AD patients.     

Different growth factor requirements for human Th2 cells may reflect in vivo induced anergy.

We previously reported the isolation of allergen-specific Th2 lines and clones from atopy patch test (APT) sites of atopic dermatitis (AD) patients. Upon stimulation with allergen or anti-CD3+ phorbol myristate acetate (PMA) IL-4 was released with or without IL-5, while no (or extremely low concentrations of) IL-2 and interferon-gamma (IFN-gamma) were detectable. A high IL-4/IFN-gamma ratio facilitates production of allergen-specific IgE, of which high levels are observed in AD patients. Here we show that the above mentioned Th2 cells are notably different from murine Th2 cells. Not IL-4, which is the autocrine acting growth factor for murine Th2 cells, but IL-2 was needed for proliferation of these human APT-derived Th2 lines and clones. Of significance, unless exogenous IL-2 was added, no proliferative response to allergen, presented by Epstein-Barr virus-transformed B (EBV-B) cells, non-T cells or IgE-bearing Langerhans cells (LC), occurred. Lack of proliferation and IL-2 production after full T cell receptor (TCR) triggering is a characteristic first described for in vitro anergized T cells. However, like the clones we describe in this study, anergic T cells may retain production of cytokines other than IL-2. A further resemblance between anergic T cells and the human Th2 clones reported here is that IL-4 can enhance IL-2-driven proliferation, but is not capable of inducing T cell growth by itself. The absence of IL-4-driven proliferation differentiates human Th2 cells from murine Th2 cells. Both produce IL-4 when stimulated in a cognate fashion, but only murine Th2 cells will proliferate. We conclude that the presently reported human Th2 cells are different from murine Th2 cells, in that they need other T cells to produce IL-2 required for their expansion. Moreover, the Th2 cells phenotypically resemble anergic T cells. As yet, however, we have no clue as to whether these features account for the current Th2 cells only or for human Th2 cells in general. We hypothesize that the Th2 phenotype of AD skin-derived, allergen-specific T cells may be induced in vivo by LC, which lack CD80, and therefore do not provide secondary signals through CD28-CD80 interaction.     

The role of IL-22 in the pathogenesis of skin diseases

IL-22 is an IL-10 family cytokine that acts mainly on epithelial cells. It is produced by immune cell subsets, including CD4? T cells, natural killer cells, and natural killer T cells. In the skin, IL-22 mediates keratinocyte proliferation and epidermal hyperplasia, inhibits terminal differentiation of keratinocytes, and induces the production of antimicrobial proteins. Although IL-22 production was initially linked with IL-17 expression in Th17 cells, IL-22 production can also occur in an apparently unique subset of cells that lacks the production of IL-17 and IFN-γ (Th22). Interestingly, Th22 cells express skin homing chemokine receptors CCR4 and CCR10. Indeed, Th22 cells reside in the normal skin and are shown to be enriched in the lesional skin of inflammatory skin diseases, indicating the importance of IL-22 in skin homeostasis and pathogenesis of skin diseases. Although psoriasis is the first example of an organ-specific immune disorder for which the role of IL-22 has been comprehensively studied, a growing body of evidence indicates that this cytokine also plays a critical role in the pathogenesis of atopic dermatitis. In this review, we discuss the role of IL-22 in the pathogenesis of skin diseases, particularly focusing on psoriasis and atopic dermatitis. Targeting IL-22 may have promise as a potential therapeutic for various skin diseases.     

Relationship between facilitated allergen presentation and the presence of allergen-specific IgE in serum of atopic patients.

Allergen presentation to allergen-specific T cells can be facilitated when IgE-allergen complexes are endocytosed by antigen-presenting cells (APC) after binding to the low-affinity Fc epsilon R type II (CD23). Here we present a study on the relative capabilities of sera of atopic patients to mediate facilitated antigen presentation (FAP). To this aim FAP was studied in an in vitro model in which CD23-expressing Epstein-Barr virus (EBV)-B cells act as APC to T lymphocyte clones (TLC) that are specific for Der p 2, a major allergen of housedust mite Dermatophagoides pteronyssinus (Dp). Der p 2 is immune-complexed by preincubation in sera from atopic patients, containing allergen-specific IgE. If EBV-B cells are preincubated with these complexes before using the cells as APC, the allergen-specific TLC proliferate at 100-1000-fold lower allergen concentration than required for T cell activation after presentation of uncomplexed allergen. The relative capability of various sera to mediate FAP was correlated with total serum IgE, and especially with Der p 2-specific serum IgE. In the model used, a high FAP capacity could be demonstrated only in sera with a total serum IgE concentration above approximately 2 micrograms/ml or with Der p 2-specific IgE above approximately 100 ng/ml. Maximal FAP, i.e. the ability to induce maximal proliferation of the TLC, was obtained in the presence of more than +/- 600 ng Der p 2-specific IgE/ml. At 100-600 ng/ml Der p 2-specific IgE the level of FAP was correlated with the concentration of allergen-specific IgE, whereas at lower concentrations FAP was low or absent. All tested sera from eczema patients, all having serum anti-Der p 2-IgE concentrations > 600 ng/ml, showed a high FAP capacity, whereas all tested sera from atopic patients without eczema, which had serum anti-Der p 2-IgE levels < 600 ng/ml, showed no or a low FAP capacity. The association of high FAP capacity with eczema may reflect a functional role of FAP in the pathogenesis of atopic dermatitis.     

The relative contribution of IL-4 and IL-13 to human IgE synthesis induced by activated CD4 or CD8 T cells

The relative contribution of IL-4 and IL-13 to the regulation of IgE synthesis has remained relatively poorly characterized, partially because of lack of suitable animal models. We have studied the roles of IL-4 and IL-13 in human IgE synthesis induced by supernatants derived from activated CD4⁺⁺ or CD8⁺ T cell clones. Neutralizing anti–IL-4 and anti–IL-13 monoclonal antibodies (mAbs) inhibited IgE synthesis induced by anti-CD40 mAbs and supernatants from CD4⁺ T cells by an average 61% and 42%, respectively (n = 25). Recombinant IL-13 had additive effects on IL-4-induced IgE synthesis, but only when IL-4 was present at low concentrations. Accordingly, IL-4 was the dominant IgE synthesis–inducing cytokine derived from highly polarized T helper (TH)₂ cells. However, anti–IL-13 mAbs also significantly inhibited IgE synthesis induced by two of three supernatants derived from allergen-specific T_H2-like cell lines generated from the skin of patients with atopic dermatitis. Furthermore, anti–IL-13 mAbs almost completely inhibited IgE synthesis induced by supernatants from T_H1 cells or CD8⁺ T cell clones. Taken together, these data indicate that IL-13, in addition to IL-4, contributes to IgE synthesis induced by all T helper cell subsets, including allergen-specific T_H2 cells. Moreover, IL-13 appears to be the major IgE synthesis–inducing cytokine derived from T_H1 cells or CD8⁺ T cells. (J Allergy Clin Immunol 1997;100:792-801.)     

CD14 promoter polymorphisms in atopic families: implications for modulated allergen-specific immunoglobulin E and G1 responses

BACKGROUND: CD14 promoter DNA sequence polymorphisms for the endotoxin receptor gene have been implicated in modulating allergen-specific immunoglobulin (Ig)E responses in randomly selected individuals with atopy. We sought to determine if a single nucleotide polymorphism in the CD14 promoter region is associated with atopy in atopic families, and to assess its influence on serum levels of CD14 and allergen-specific IgE and IgG1 responses. METHODS: We screened 367 members of 91 Caucasian nuclear families with a history of asthma for pulmonary function by spirometry, including methacholine challenge to detect bronchial hyperreactivity, and atopy by serum total IgE and skin prick test to 14 allergens. The CD14 promoter single nucleotide polymorphism was analyzed in DNA isolated from peripheral blood mononuclear cells to identify C/C, C/T and T/T genotypes. Serum tests were done for soluble CD14 (sCD14) and dust mite-specific antibody (Der p 1-IgG1). RESULTS: Serum sCD14 levels were not associated with clinical phenotypes (asthma, bronchial hyperreactivity or atopy). However, sCD14 levels were inversely related to both allergen-specific IgE and Der p 1-IgG1 production, but only among those with evidence of atopic sensitization. Linear regression analysis, accounting for random family effects, demonstrated a higher production of allergen-specific IgE or Der p 1-IgG1 associated with the T/T genotype and a lower level of specific IgE and IgG1 production associated with sCD14 levels. CONCLUSIONS: An element of the innate immune system (CD14) has profound effects upon modulating the acquired allergen-specific immunoglobulin responses among those with an inherited atopic predisposition.     

The disease progression in the keratin 14 IL-4-transgenic mouse model of atopic dermatitis parallels the up-regulation of B cell activation molecules, proliferation and surface and serum IgE

We have previously characterized the keratin 14 interleukin-4-transgenic (IL-4-Tg) mouse model of atopic dermatitis as a chronic pruritic inflammatory skin disease typified by skin infiltration of inflammatory cells and early up-regulation of Th2 cytokines and late surge of Th1 cytokines. In the present study, we examined the involvement of B cells. Systematic examinations of the following immunological parameters on B cells were carried out in non-Tg control mice and in IL-4-Tg mice at before disease onset and early and late disease stages so that we could determine the immunological sequence of events leading to the disease development: surface expressions of IA/IE, activation and costimulatory molecules, proliferation under LPS or IgM stimulation, quantification of cell surface and serum IgE, IgG1, and IgG2a. Our results showed that as the disease progresses from before onset to early disease and to late disease, there is a parallel increase in surface markers of B cell activation (IA/IE, CD44, CD69, CD80 and CD86), in B cell proliferation, and in cell surface and serum IgE. Significant increases of Th2-driven serum IgG1 and IgE in early disease was followed by significant increase of Th1-driven IgG2a in late disease. Importantly the significant increases of activation molecule (IA/IE), proliferation (to LPS), and surface IgE on B cells of the IL-4-Tg mice precedes the up-regulation of serum IgE and disease onset. These data suggest that activated B cells may play a role in atopic dermatitis disease development by up-regulating serum IgE concentration, which serves as a marker of disease onset.     

Immune regulation in atopic dermatitis

Atopic dermatitis is a chronic inflammatory skin disease with a pathogenesis of complex immune dysregulation and interplay of genetic, environmental and psychological factors. Activation and skin-selective homing of peripheral-blood T cells, and effector functions in the skin, represent sequential immunological events in the pathogenesis of atopic dermatitis. Both CD4(+) and CD8(+) T cells bearing the cutaneous-lymphocyte-associated antigen represent activated memory/effector T cell subsets and induce IgE, mainly via IL-13, and prolong eosinophil lifespan, mainly via IL-5. Dysregulated apoptosis in skin-homing T cells and keratinocytes contributes to the elicitation and progress of atopic dermatitis. T cell survival is enhanced in the skin by cytokines and extracellular-matrix proteins. These activated T cells induce keratinocyte apoptosis, leading to eczema formation.     

Prominent involvement of activated Th1-subset of T-cells and increased expression of receptor for IFN-gamma on keratinocytes in atopic dermatitis acute skin lesions

BACKGROUND: Atopic dermatitis (AD) is an allergic skin disease mediated by antigen-specific IgE and an important role has been ascribed to CD4+ cells (Th cells). The objective of the study was to evaluate humoral and cellular immunological factors in the blood and the skin lesions of AD patients, and to analyze the presence of inflammatory cell-surface markers in blood and skin biopsies. METHODS: The parameters for monitoring of 40 AD patients included results of prick test to inhalant allergens and epicutaneous (patch) test to contact allergens; values of total IgE, serum immunoglobulins (IgG, IgA, IgM) and different cell markers in the sera (CD3, CD4, CD8, CD20, CD21, CD23, HLA-DR). We also analyzed the presence of inflammatory cell-surface markers (CD3, CD4, CD8, CD20, CD20, CD1a, CD23, CD29, CD45Ro, IFNgamma+ markers) in the biopsies of skin lesions from 10 AD patients and 5 healthy controls (HCs) by immunohistochemical analysis (method of avidin-biotin immunoperoxidase). RESULTS: Beside increased total serum IgE and positive skin tests, a significantly higher percentage of CD23+ cells with lower percentage of CD21+ cells was revealed in peripheral blood of AD patients in comparison to HCs. A positive epidermal expression of the majority of markers of T cells (CD3+, CD4+, CD8+, CD29+, CD45Ro+, IFNgamma+) and those of Langerhans' cells (LCs) (CD1a, CD23+), without those of B cells (CD20+) were noted in AD patients, but no in the skin of HCs. Furthermore, significant difference was also found between the two groups for increased expression of CD3, CD4, CD8, CD29, CD45Ro, IFNgamma+ markers (markers for IFNgamma receptor) and higher intraepidermal CD23+ LCs and intradermal CD1a+ LCs in AD skin lesions. CONCLUSIONS:The obtained results suggest involvement of various humoral factors with increased production of IgE and cooperation between Th subsets and LCs, with higher production of related cytokines, and disturbed cellular immunity, including epidermal LCs with IgE receptors of high and low affinity in AD. The annotation of activated Th1 cells with increased producing of IFNgamma in acute AD skin lesions is notable, and might lead to IFNgamma binding to keratinocytes and consequently inflammatory skin changes in the disease.     

Cutaneous CD30+ cells in children with atopic dermatitis

BACKGROUND: CD30 expression can be considered a marker of Th2 cells. We investigated the presence of CD30+ cells in the lesional skin of children with atopic dermatitis (AD). We also analyzed the possible relationship between CD30+ cells and serum soluble CD 30 (sCD30) levels, and IgE, soluble interleukin-2 (IL-2) receptor (sIL-2R) or soluble CD23 (sCD23) levels in the blood, and clinical score. METHODS: Ten eczematous children (4 males, 6 females; median age: 4 years and 5 months; range: 11 months to 14 years), 9 sex- and age-matched control children and an adult control group were studied. A clinical score (SCORAD index), was given to eczematous lesions. Blood was taken for the determination of IgE, sCD30, sIL-2R and sCD23 levels. Punch biopsies of lesional skin were stained with hematoxylin and eosin or incubated with anti-CD30 monoclonal antibodies. Skin prick tests (SPTs) were also performed. RESULTS: In the biopsy specimens, CD30 expression was observed in high proportions of infiltrating cells. In children with AD, total serum IgE, sCD30, sIL-2R, sCD23 and eosinophils were significantly elevated compared to controls. CD30+ cells were not associated with serum IgE, sCD30, sIL-2R, sCD23, or SPT results, score of inflammatory cells in lesional skin or clinical score. Children with AD who had high total IgE and specific IgE antibodies did not differ from those with normal total IgE and negative specific IgE in respect of age, clinical score, number of CD30+ cells, sCD30, sIL-2R and sCD23 levels, score of inflammatory cells in skin or clinical score. CONCLUSION: Our results showed remarkable numbers of CD30+ cells in the lesional skin and high sCD30 in the serum of children with AD. CD30+ cells did not correlate with systemic markers of IgE reaction.     

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

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

The development of atopic dermatitis is independent of Immunoglobulin E up-regulation in the K14-IL-4 SKH1 transgenic mouse model

Background We have successfully generated an IgE‐associated (extrinsic/allergic) mouse model of atopic dermatitis in K14‐IL‐4‐Tg/CByB6 mice. The newly described subset of non‐IgE‐associated (intrinsic/non‐allergic) atopic dermatitis in human patients raises the question on the role of IgE in the pathogenesis. Objective The aim of this study was to develop a non‐IgE‐associated atopic dermatitis model in K14‐IL‐4‐Tg/SKH1 mice. Methods K14‐IL‐4‐Tg/CByB6 mice were crossed with SKH1 mice to produce K14‐IL‐4‐Tg/SKH1 mice. Phenotypes of clinical and histological, cytokine expression in the skin lesions, and total serum IgE in K14‐IL‐4‐Tg/CByB6 and K14‐IL‐4‐Tg/SKH1 mice were compared. The CD40 and CD40L on T and B cells were also studied to differentiate their roles in IgE production. Results K14‐IL‐4‐Tg/SKH1mice had a normal total serum IgE level and manifested a chronic inflammatory skin phenotype identical to that of K14‐IL‐4‐Tg/CByB6 IgE‐mediated mice in clinical morphology, histology, infiltration of mononuclear cells/eosinophils/mast cells, mast cell degranulation, and up‐regulation of chronic lesional cytokine mRNA expression of IL‐1β, IL‐3, IL‐4, IL‐6, IL‐10, IL‐12, IL‐13, IFN‐γ, TNF‐α, and TNF‐β. We also found that the inability of CD4⁺ T cells of the K14‐IL‐4‐Tg/SKH1mice to up‐regulate CD40L expression upon stimulation might account for their inability to up‐regulate the IgE level. B cell abnormality was ruled out as CD19⁺ B cells of K14‐IL‐4‐Tg/SKH1 mice synthesized the same amount of IgE in vitro compared with K14‐IL‐4‐Tg/CByB6 mice in the presence of IL‐4 and soluble CD40L. Our studies further suggested that the defect of early growth response‐1 in T cells might be responsible for the impaired CD40L up‐regulation in K14‐IL‐4‐Tg/SKH1 mice. Conclusion K14‐IL‐4‐Tg/SKH1 mice developed skin inflammation that resembled human intrinsic atopic dermatitis. Therefore, this model may be suitable to study the pathogenesis of intrinsic atopic dermatitis.     

Human memory Th17 cells express a functional histamine H4 receptor

The histamine H4 receptor is functionally expressed on CD4(+) T cells and in particular on human CD4(+) Th2-polarized T cells. Interleukin (IL)-17-producing T cells (Th17 cells) represent a newly defined major CD4(+) T-cell subset, having been identified in psoriatic plaques and in acute skin lesions of atopic dermatitis where histamine is also present in high concentrations. To elucidate the role of the histamine H4 receptor (H4R) on these effector T cells, we polarized human memory T cells into Th17 cells. Further, we investigated H4R expression and assessed its function by real-time PCR, by a cytokine secretion assay of IL-17, and by electrophoretic mobility shift assay of activating protein-1 (AP-1). We show that Th17 cells polarized by IL-1β together with IL-23 express the H4R on mRNA and protein level. Additionally, we identified IL-17-positive cells in psoriatic skin lesions. The IL-17-positive lymphocytes were all positive also for functional H4R. Stimulation with histamine or a H4R agonist increased the production of IL-17 and induced activating protein-1 in Th17 cells. In inflammatory skin diseases with enhanced histamine release, such as psoriasis and atopic dermatitis, histamine might foster the immunomodulatory potency of skin-infiltrating Th17 cells.     

Murine model of atopic dermatitis associated with food hypersensitivity

BACKGROUND: Atopic dermatitis (AD) is an eczematous skin eruption that generally begins in early infancy and affects up to 12% of the population. The cause of this disorder is not fully understood, although it is frequently the first sign of atopic disease and is characterized by an elevated serum IgE level, eosinophilia, and histologic tissue changes characterized early by spongiosis and a CD4(+) T(H)2 cellular infiltrate. Hypersensitivity to foods has been implicated as one causative factor in up to 40% of children with moderate-to-severe AD. OBJECTIVE: The purpose of this study was to establish a murine model of food-induced AD. METHODS: Female C3H/HeJ mice were sensitized orally to cow's milk or peanut with a cholera toxin adjuvant and then subjected to low-grade allergen exposure. Histologic examination of skin lesions, allergen-specific serum Ig levels, and allergen-induced T-cell proliferation and cytokine production were examined. RESULTS: An eczematous eruption developed in approximately one third of mice after low-grade exposure to milk or peanut proteins. Peripheral blood eosinophilia and elevated serum IgE levels were noted. Histologic examination of the lesional skin revealed spongiosis and a cellular infiltrate consisting of CD4(+) lymphocytes, eosinophils, and mast cells. IL-5 and IL-13 mRNA expression was elevated only in the skin of mice with the eczematous eruption. Treatment of the eruption with topical corticosteroids led to decreased pruritus and resolution of the cutaneous eruption. CONCLUSION: This eczematous eruption resembles AD in human subjects and should provide a useful model for studying immunopathogenic mechanisms of food hypersensitivity in AD.