Regulation of isotype switching

IL-33 Enhances the Total Production of IgG, IgG1, and IgG3 in Angiostrongylus cantonensis-Infected Mice

The purpose of this study is to clarify the role of IL-33 in the immune response to angiostrongyliasis, especially in terms of antibody production and isotype switching. In our experiment, C57BL/6 mice were each infected with 35 infectious larvae and were divided into groups that received an intraperitoneal injection of IL-33, anti-IL-33 monoclonal antibody (mAb), or anti-ST2 mAb 3 days post-infection (dpi) and were subsequently administered booster shots at 5-day intervals with the same dose. Serum samples from each group were collected weekly for ELISA assays. The levels of total IgG, IgG1, and IgG3 were significantly increased in A. cantonensis-infected mice that were treated with IL-33, and the levels decreased significantly in infected groups treated with anti-IL-33 or anti-ST2 mAb. These results suggest that IL-33 may play a critical role in the pathogenesis of human angiostrongyliasis and could be useful for understanding protective immunity against this parasitic infection.

Tobacco Smoking Could Accentuate Epithelial-Mesenchymal Transition and Th2-Type Response in Patients With Chronic Rhinosinusitis With Nasal Polyps

Tobacco smoking (TS) has been known as one of the most potent risk factors for airway inflammatory diseases. However, there has been a paucity of information regarding the immunologic alteration mediated by TS in patients with chronic rhinosinusitis with nasal polyps (CRSwNP). To identify the effect of TS, we harvested human tissue samples (never smoker: n=41, current smoker: n=22, quitter: n=23) and analyzed the expression of epithelial-derived cytokines (EDCs) such as IL-25, IL-33, and thymic stromal lymphopoietin. The expressions of Th2 cytokines and total serum IgE showed a type-2 inflammatory alteration by TS. In addition, the epithelial marker E-cadherin and epithelial-mesenchymal transition (EMT)-associated markers (N-cadherin, α-SMA, and vimentin) were evaluated. Histological analysis showed that EDC expressions were upregulated in the current smoker group and downregulated in the quitter group. These expression patterns were consistent with mRNA and protein expression levels. We also found that the local Th2 cytokine expression and IgE class switching, as well as serum IgE levels, were elevated in the current smoker group and showed normal levels in the quitter group. Furthermore, the expressions of E-cadherin decreased while those of N-cadherin, α-SMA, and vimentin increased in the current smoker group compared those in the never smoker group. Taken together, these results indicate that TS contributes to the deterioration of pathogenesis by releasing local EDCs and Th2 cytokines, resulting in EMT in patients with CRSwNP. We verified that alterations of immunological response by TS in sinonasal epithelium can play a vital role in leading to CRSwNP.

Sestrin2 Mediates IL-4-induced IgE Class Switching by Enhancing Germline ε Transcription in B Cells

Sestrin2 (Sesn2), a metabolic regulator, accumulates in response to a diverse array of cellular stresses. Sesn2 regulates cellular metabolism by inhibiting the mammalian target of rapamycin complex 1 through the AMP-activated protein kinase (AMPK) signaling pathway. Recently, researchers reported that Sesn2 regulates the differentiation and function of innate immune cells and T cells; however, the role of Sesn2 in B cells is largely unknown. In this study, we investigated the role of Sesn2 in Ig class switching and Ig production in mouse B cells. We observed that mouse B cells express Sesn2 mRNA. Interestingly, the expression of germline ε transcripts (GLTε) was selectively decreased in lipopolysaccharide-stimulated Sesn2^−/− splenocytes. Overexpression of Sesn2 increased GLTε promoter activity in B cells. In addition, AICAR (an activator of AMPK) selectively increased IL-4-induced GLTε expression and surface IgE (sIgE) expression in splenocytes. Furthermore, AICAR selectively enhanced IL-4-induced GLTε expression, sIgE expression, and IgE production by anti-CD40-stimulated B cells. We observed that ovalbumin (OVA)-specific IgE concentration was reduced in OVA-challenged Sesn2^−/− mice. Taken together, these results indicate that Sesn2-AMPK signaling selectively enhances IL-4-induced IgE class switching and IgE production by B cells, suggesting that this could be a therapeutic strategy targeting Sesn2 in IgE-mediated allergic diseases.

IFNγ is Required for Optimal Antibody-Mediated Immunity against Genital Chlamydia Infection

Defining the mechanisms of immunity conferred by the combination of antibody and CD4⁺ T cells is fundamental to designing an efficacious chlamydial vaccine. Using the Chlamydia muridarum genital infection model of mice, which replicates many features of human C. trachomatis infection and avoids the characteristic low virulence of C. trachomatis in the mouse, we previously demonstrated a significant role for antibody in immunity to chlamydial infection. We found that antibody alone was not protective. Instead, protection appeared to be conferred through an undefined antibody-cell interaction. Using gene knockout mice and in vivo cellular depletion methods, our data suggest that antibody-mediated protection is dependent on the activation of an effector cell population in genital tract tissues by CD4⁺ T cells. Furthermore, the CD4⁺ T cell-secreted cytokine gamma interferon (IFN-γ) was found to be a key component of the protective antibody response. The protective function of IFN-γ was not related to the immunoglobulin class or to the magnitude of the Chlamydia-specific antibody response or to recruitment of an effector cell population to genital tract tissue. Rather, IFN-γ appears to be necessary for activation of the effector cell population that functions in antibody-mediated chlamydial immunity. Our results confirm the central role of antibody in immunity to chlamydia reinfection and demonstrate a key function for IFN-γ in antibody-mediated protection.

Effects of low-dose light-emitting-diode therapy in combination with water bath for atopic dermatitis in NC/Nga mice

BACKGROUND

Light-emitting diode (LED) phototherapy and water bath therapy have beneficial effect on atopic dermatitis (AD)-like skin disease. However, not all current treatments work well and alternative therapies are need. The contribution of combination therapy with low-dose 850 nm LED and water bath was investigated on dermatophagoides farina (Df)-induced dermatitis in NC/Nga mice.

METHODS

Low-dose LED (10, 15, and 20 J/cm(2) ) irradiation, water bath (36 ± 1°C) were administered separately and together to the Df-induced NC/Nga mice in acrylic jar once a day for 2 weeks.

RESULTS

Combined therapy with low-dose LED therapy and water bath therapy significantly ameliorated the development of AD-like skin lesions. These effects were correlated with the suppression of total IgE, NO, histamine, and Th2-mediated immune responses. Furthermore, combination therapy significantly reduced the infiltration of inflammatory cells and the induction of thymic stromal lymphopoietin (TSLP) in the skin lesions. The beneficial therapeutic effects of this combination therapy might regulate by the inhibition of various immunological responses including Th2-mediated immune responses, inflammatory mediators such as IgE, histamine, and NO, as well as inflammatory cells.

CONCLUSIONS

The combination therapy of LED and water bath might be used as an efficacious, safe, and steroid-free alternative therapeutic strategy for the treatment of AD.

Food allergies: the basics

IgE-associated food allergy affects approximately 3% of the population and has severe effects on the daily life of patients-manifestations occur not only in the gastrointestinal tract but also affect other organ systems. Birth cohort studies have shown that allergic sensitization to food allergens develops early in childhood. Mechanisms of pathogenesis include cross-linking of mast cell- and basophil-bound IgE and immediate release of inflammatory mediators, as well as late-phase and chronic allergic inflammation, resulting from T-cell, basophil, and eosinophil activation. Researchers have begun to characterize the molecular features of food allergens and have developed chip-based assays for multiple allergens. These have provided information about cross-reactivity among different sources of food allergens, identified disease-causing food allergens, and helped us to estimate the severity and types of allergic reactions in patients. Importantly, learning about the structure of disease-causing food allergens has allowed researchers to engineer synthetic and recombinant vaccines.

7,3',4'-Trihydroxyisoflavone Ameliorates the Development of Dermatophagoides farinae-Induced Atopic Dermatitis in NC/Nga Mice

Atopic dermatitis is an inflammatory and chronically relapsing skin disorder that commonly occurs in children; the number of atopic dermatitis patients is increasing. The cause and mechanism of atopic dermatitis have not been defined clearly, although many studies are ongoing. Epidemiological studies suggest that soybean and its isoflavones have immunoregulatory activities. Here, we report that 7,3′,4′-trihydroxyisoflavone (7,3′,4′-THIF), a major metabolite of daidzin, effectively inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO), tumor necrosis factor (TNF)-α, and interleukin (IL)-6 production in RAW 264.7 cells, and also reduced β-hexosaminidase secretion in RBL-2H3 cells. Moreover, 7,3′,4′-THIF significantly reduced scratching time, transepidermal water loss, and mast cell infiltration. It also decreased protease-activated receptor (PAR)-2 and IL-4 expression and increased filaggrin expression in skin lesions of NC/Nga mice. These results suggest that 7,3′,4′-THIF improves Dermatophagoides farina body extract-induced atopic dermatitis in NC/Nga mice.

Administration of poly(I:C) improved dermatophagoides farinae-induced atopic dermatitis-like skin lesions in NC/Nga mice by the regulation of Th1/Th2 balance

Atopic dermatitis (AD) is characterized by a chronic and replapsing skin disease with Th2-dominant allergic inflammation. Poly(I:C) has been shown to have immunopotentiator properties, but its effect on AD has not been examined. In this study, the immunomodulatory effects of poly(I:C), using dermatophagoides farinae (Df)-induced AD-like skin lesions in NC/Nga mice, were investigated. The clinical scores were reduced significantly by the treatment with poly(I:C) at 25 and 50 μg/mouse. Histological analysis of the skin also revealed that treatment of poly(I:C) at 25 and 50 μg/mouse significantly reduced the inflammatory cellular infiltrate, including mast cells and eosinophils. Moreover, poly(I:C) increased the level of IFN-γ, a Th1 cytokine, whereas decreasing that of selective Th2 cytokine both in vivo and in vitro. The levels of serum IgE and Th2 chemokines such as eotaxin, TARC, in spleen cells were also reduced by poly(I:C). These results suggest that poly(I:C) inhibit the development of Df-induced AD-like skin lesions in NC/Nga mice through regulation of the Th1/Th2 balance. Therefore, our results indicate that poly(I:C) might be a useful immunomodulatory agent for the treatment of human AD.

Glucosamine improved atopic dermatitis-like skin lesions in NC/Nga mice by inhibition of Th2 cell development

Dysregulated Th subset responses, characterized by Th2-dominant allergic inflammation, are thought to be central to the pathogenesis of atopic dermatitis (AD). Glucosamine has been shown to have immunosuppressive properties, but its effect on AD has not been examined. In this study, the immunoregulatory effects of glucosamine, using dermatophagoides farinae (Df)-induced AD-like skin lesions in NC/Nga mice, were investigated. The clinical scores were reduced significantly by the treatment with glucosamine at 10 and 20 mg/day. Histological analysis of the skin also revealed that treatment of glucosamine at 10 and 20 mg/day significantly reduced the inflammatory cellular infiltrate, including mast cells and eosinophils. The levels of serum IgE and Th2 cytokines in spleen cells were reduced, whereas no significant change was detected in IFN-γ, a Th1 cytokine. To determine the mechanism associated with inhibition of the Th2 immune response, the effects of glucosamine on the selective differentiation pathway of the Th subset in vitro was examined in NC/Nga mice. The results showed that glucosamine suppressed the differentiation of naïve CD4(+) T cells to Th2 cells in vitro. On the basis of in vivo and in vitro results of the NC/Nga mice, the immunobiological effects of glucosamine on peripheral blood mononuclear cells from patients with AD were examined. The production of Th2 cytokines, such as IL-4 and IL-5, was significantly decreased after in vitro administration of glucosamine, which suggest that glucosamine might be a useful immunomodulatory agent for the treatment of human AD.

Pro/Con debate: Is occupational asthma induced by isocyanates an immunoglobulin E-mediated disease?

Isocyanates, low-molecular weight chemicals essential to polyurethane production, are one of the most common causes of occupational asthma, yet the mechanisms by which exposure leads to disease remain unclear. While isocyanate asthma closely mirrors other Type I Immune Hypersensitivity (Allergic) disorders, one important characteristic of hypersensitivity ('allergen'-specific IgE) is reportedly absent in a large portion of affected individuals. This variation from common environmental asthma (which typically is induced by high-molecular weight allergens) is important for two reasons. (1) Allergen-specific IgE is an important mediator of many of the symptoms of bronchial hyper-reactivity in 'allergic asthma'. Lack of allergen-specific IgE in isocyanate hypersensitive individuals suggests differences in pathogenic mechanisms, with potentially unique targets for prevention and therapy. (2) Allergen-specific IgE forms the basis of the most commonly used diagnostic tests for hypersensitivity (skin prick and RAST). Without allergen-specific IgE, isocyanates may go unrecognized as the cause of asthma. In hypersensitive individuals, chronic exposure can lead to bronchial hyperreactivity that persists years after exposure ceases. Thus, the question of whether or not isocyanate asthma is an IgE-mediated disease, has important implications for disease screening/surveillance, diagnosis, treatment and prevention. The present Pro/Con Debate, addresses contemporary, controversial issues regarding IgE in isocyanate asthma.

IL-21: a new player in the control of isotype switch in Peyer's patches

Peyer's patches (PP) are lymphoid follicles of the small intestine containing predominantly IgA(+) B cells. In this JLB issue, IL-21 is reported to dampen TGF-beta1-induced IgG2b but not IgA production by mouse B cells, possibly explaining why IgA(+) B cells predominate in PP.

PAS-1, a protein from Ascaris suum, modulates allergic inflammation via IL-10 and IFN-gamma, but not IL-12

Helminths and their products have a profound immunomodulatory effect upon the inductive and effector phases of inflammatory responses, including allergy. We have demonstrated that PAS-1, a protein isolated from Ascaris suum worms, has an inhibitory effect on lung allergic inflammation due to its ability to down-regulate eosinophilic inflammation, Th2 cytokine release and IgE antibody production. Here, we investigated the role of IL-12, IFN-gamma and IL-10 in the PAS-1-induced inhibitory mechanism using a murine model of asthma. Wild type C57BL/6, IL-12(-/-), IFN-gamma(-/-) and IL-10(-/-) mice were immunized with PAS-1 and/or OVA and challenged with the same antigens intranasally. The suppressive effect of PAS-1 was demonstrated on the cellular influx into airways, with reduction of eosinophil number and eosinophil peroxidase activity in OVA+PAS-1-immunized wild type mice. This effect well correlated with a significant reduction in the levels of IL-4, IL-5, IL-13 and eotaxin in BAL fluid. Levels of IgE and IgG1 antibodies were also impaired in serum from these mice. The inhibitory activity of PAS-1 was also observed in IL-12(-/-) mice, but not in IFN-gamma(-/-) and IL-10(-/-) animals. These data show that IFN-gamma and IL-10, but not IL-12, play an important role in the PAS-1 modulatory effect.

S epsilon S mu and S epsilon S gamma switch circles in human nasal mucosa following ex vivo allergen challenge: evidence for direct as well as sequential class switch recombination

B cells switch to IgE under the influence of IL-4, IL-13, and CD40 costimulation through a multistep process involving epsilon germline transcription and class switch recombination. Classically, switching has been considered an event restricted to lymphoid tissues; however, epsilon germline transcripts (I(initiator)epsilon RNA) have been observed within lung, sinus, and nasal tissue of individuals with asthma, sinusitis, and rhinitis. Furthermore, nasal mucosal tissue from allergic rhinitics produces epsilon germline transcripts following ex vivo allergen challenge. Collectively, these studies raised the possibility that switching to IgE may occur locally, at sites of allergic inflammation. Although epsilon germline transcripts are considered necessary to target the IgE locus, it is class switch recombination that ultimately leads to de novo IgE production. In this study, we demonstrate that S epsilon S mu DNA switch circles (products of class switch recombination) as well as I epsilon and C epsilon RNA are produced within nasal tissue from allergic individuals following ex vivo allergen challenge. epsilon germline transcription was inhibited when tissue was cultured with a combination of allergen and neutralizing Abs against IL-4 and IL-13, indicating that de novo cytokine production mediated the isotype switch. We also show allergen-induced appearance of S epsilon S gamma DNA switch circles and up-regulation of C gamma 4 mRNA, illustrating that sequential switching to IgE also occurred. This work strongly suggests that B cells residing within the nasal mucosa undergo switching to IgE in the context of a local immune response to allergen.

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.

1alpha,25-dihydroxyvitamin D3 inhibits anti-CD40 plus IL-4-mediated IgE production in vitro

In the present study, we examined whether anti-CD40+IL-4-mediated B cell proliferation and immunoglobulin synthesis is affected by vitamin D (VD) and its low-hypercalcemic analogue EB1089 in Bcells from healthy donors. Analysis of vitamin D receptor (VDR) expression showed that only anti-CD40+IL-4-stimulated, but not resting B cells express VDR. Studies on B cell proliferation revealed that anti-CD40+IL-4-mediated proliferation of B cells was not affected by VD or EB1089. By contrast, IgE synthesis was markedly inhibited by both, VD and EB1089, starting at concentrations from 10(-10) M for VD and 10(-12) M for EB1089, with maximal inhibition at 10(-6) M (VD 85.5+/-9.7%; EB1089 77.3+/-10.8%). The production of the other Ig (IgA and IgG) was not significantly inhibited by VD after anti-CD40+IL-4 stimulation, and IgM production was only slightly reduced (18.7+/-7.9%). These observations were confirmed by intracellular staining of the different isotypes in B cells after anti-CD40+IL-4 stimulation, which showed a strong reduction of IgE(+) cells in the presence of VD. Analyses of molecules that are known to affect IgE production (CD23 and IL-6) revealed that these are not involved in VD-dependent inhibition of IgE production. By contrast, epsilon germ-line transcription was inhibited by VD (41.2+/-26.1%; n=5), as was NF-kappaB (p50 and p65) protein expression in stimulated cells. These data show that VD and its analogue EB1089 inhibit IgE production of anti-CD40+IL-4-stimulated B cells in vitro. The involved mechanism includes epsilon germ-line transcription, NF-kappaB activation and switch recombination suggesting that complex mechanisms of VD action in anti-CD40+IL-4-stimulated B cells are responsible.

Lipoteichoic acid from Staphylococcus aureus induces Th2-prone dermatitis in mice sensitized percutaneously with an allergen

BACKGROUND

We found previously that lipoteichoic acid (LTA) from Staphylococcus aureus has the ability to induce Th2 cytokine production by peripheral blood mononuclear cells (PBMC) from patients with atopic dermatitis (AD). However, it is not known whether LTA can induce a Th2-dominant cytokine response in the skin of AD patients.

OBJECTIVE

The purpose of this study was to determine the effects of LTA in mice sensitized percutaneously with a house dust mite antigen (MA) through barrier-disrupted skin, as an experimental animal model of AD.

METHODS

Mice were sensitized with MA by a single topical application to barrier-disrupted abdominal skin. Seven days after the sensitization, the mice were challenged on the dorsal skin by LTA to elicit localized skin inflammation. The cytokine response in the dorsal skin was investigated by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistological analysis. The infiltration of inflammatory cells in the skin was also observed by histological staining.

RESULTS

Injection of LTA into the dorsal skin of MA-sensitized mice, which show a Th2-dominant cytokine response against the homologous antigen, increased the expression of mRNA for IFN-gamma, IL-4 and IL-5, but not IL-2. Immunohistological analysis demonstrated that levels of IFN-gamma, IL-4 and IL-5 transcripts corresponded with those of protein synthesis. In addition, the dorsal skin of MA-sensitized mice challenged with LTA showed significantly increased numbers of neutrophils, eosinophils, mononuclear cells and mast cells compared with control mice challenged with LTA.

CONCLUSION

These results suggest that LTA has the ability to induce localized Th2-prone dermatitis in an allergen-independent manner in the skin of AD patients and may explain the role of colonization with S. aureus in AD patients.

Evolution of IgM, IgE and IgG(1-4 )antibody responses in early childhood monitored with recombinant allergen components: implications for class switch mechanisms

The formation of IgE antibodies against environmental allergens represents the hallmark of type I allergy. Data from in vitro cultured cells and experimental animal models provide controversial evidence for isotype switching from IgM to IgE production via sequential as well as non-sequential (i.e. direct) class switch. We analyzed the evolution of IgE responses in 11 children developing birch pollen and/or grass pollen allergy during the first 7 years of life using purified recombinant allergen molecules (major birch pollen allergen, Bet v 1; major timothy grass pollen allergens, Phl p 1, Phl p 2, Phl p 5). Demographic, clinical and serological data indicated a postnatal sensitization to pollen allergens. A parallel development of IgG(1-4) and IgE responses to recombinant allergen molecules compatible with a strictly sequential class switch to IgE was observed only in one child. The only partly synchronized and dissociated development of allergen-specific antibody responses found in all other cases can be best explained by a partly sequential class switch involving few switch stations or, more likely, by direct class switching. Kinetics and courses of allergen-specific antibody responses (IgM, IgG(1-4), IgE) during the first years of life suggest that, once established, allergen-specific IgE responses are driven by antigen contact rather than by cytokines controlling class switch to IgE.

Basophil recruitment and IL-4 production during human allergen-induced late asthma

BACKGROUND

Basophils represent an important source of inflammatory mediators and cytokines after IgE-dependent activation in human beings.

OBJECTIVE

To assess the role of basophils in allergic asthma, we measured the number of basophils in the bronchial mucosa and their capacity to express IL-4 mRNA and protein during allergen-induced late asthmatic responses.

METHODS

Fiberoptic bronchoscopic bronchial biopsies were obtained at 24 hours from sites of segmental bronchial allergen challenge and control sites in 19 patients with atopic asthma and 6 nonatopic healthy volunteers. Basophil numbers were assessed by immunohistochemistry through use of mAb 2D7. IL-4 mRNA--positive cells were detected through use of in situ hybridization and colocalized to basophils through use of sequential immunohistochemistry/in situ hybridization. IL-4 protein was detected and colocalized to basophils through use of dual immunohistochemistry.

RESULTS

After allergen challenge, there was an increase in the median number of 2D7-positive basophils per square millimeter in the bronchial mucosa in patients with asthma (0.9 cells/mm(2) at baseline to 8.8 cells/mm(2) after challenge; P =.002), which also was significantly higher than what was seen in nonasthmatic controls (P =.01). Similarly, IL-4 mRNA--positive cells were increased at 24 hours in patients with asthma (1.4 to 14) in comparison with controls (0 to 0; P =.02). Colocalization studies revealed that 15% and 41% of the basophil population in patients with asthma after allergen-challenge expressed, respectively, IL-4 mRNA and protein. Conversely, 19% of IL-4 mRNA-positive cells and 72% of IL-4 protein--positive cells were accounted for by basophils.

CONCLUSION

After allergen provocation in sensitive patients with atopic asthma, basophils are recruited to the bronchial mucosa and express IL-4 mRNA and protein, which might contribute to local IgE synthesis and/or tissue eosinophilia or other aspects of allergic inflammation during late responses and ongoing asthma.

Glucocorticoids upregulate CD40 ligand expression and induce CD40L-dependent immunoglobulin isotype switching

IL-4 and CD40 ligation are essential for IgE synthesis by B cells. We have shown previously that hydrocortisone (HC) induces IgE synthesis in IL-4-stimulated human B cells. In this study we demonstrate that HC fails to induce IgE synthesis in B cells from CD40 ligand-deficient (CD40L-deficient) patients. Disruption of CD40L-CD40 interactions by soluble CD40-Ig fusion protein or anti-CD40L mAb blocked the capacity of HC to induce IgE synthesis in normal B cells. HC upregulated CD40L mRNA expression in PBMCs and surface expression of CD40L in PBMCs as well as in purified populations of T and B cells. Upregulation of CD40L mRNA in PBMCs occurred 3 hours after stimulation with HC and was inhibited by actinomycin D. Upregulation of CD40L mRNA and induction of IgE synthesis by HC were inhibited by the steroid hormone receptor antagonist RU-486. These results indicate that ligand-mediated activation of the glucocorticoid receptor upregulates CD40L expression in human lymphocytes.

Roles of TH1 and TH2 cytokines in a murine model of allergic dermatitis

Skin lesions in atopic dermatitis (AD) are characterized by hypertrophy of the dermis and epidermis, infiltration by T cells and eosinophils, and expression of the cytokines IL-4, IL-5, and IFN-gamma. The role of these cytokines in the pathogenesis of AD is not known. We took advantage of a recently described murine model of AD elicited by epicutaneous sensitization with ovalbumin (OVA) (1) and of the availability of mice with targeted deletions of the IL-4, IL-5, and IFN-gamma cytokine genes to assess the role of these cytokines in this model.OVA-sensitized skin from IL-5(-/-) mice had no detectable eosinophils and exhibited decreased epidermal and dermal thickening. Sensitized skin from IL-4(-/-) mice displayed normal thickening of the skin layers but had a drastic reduction in eosinophils and a significant increase in infiltrating T cells. These findings were associated with a reduction in eotaxin mRNA and an increase in mRNA for the T-cell chemokines macrophage inflammatory protein-2 (MIP-2), MIP-1beta, and RANTES. Sensitized skin from IFN-gamma-/- mice was characterized by reduced dermal thickening. These results suggest that both the TH2 cytokines IL-4 and IL-5 and the TH1 cytokine IFN-gamma play important roles in the inflammation and hypertrophy of the skin in AD.

Increased frequencies of allergen-induced interleukin-13-producing cells in atopic individuals during the pollen season

We have reported previously that allergen-specific serum IgE levels were correlated with allergen-induced interleukin (IL)-4 in type I allergic individuals. Here, we wanted to investigate whether IL-13, another switch factor for IgE, was induced by allergen in vitro and if so, whether this was correlated with the elevated serum IgE-levels seen in atopic individuals, and whether the cytokine profile changed during pollen season. Peripheral blood mononuclear cells from 14 atopic and 14 healthy individuals collected out of the pollen season were incubated in vitro with allergens (birch or timothy) and the number of IL-4, IL-13, IL-10 and IFN-gamma producing cells was determined by ELISPOT. In response to the specific allergen, IL-13-producing cells were seen in allergic but not in healthy individuals. The number of IL-13-producing cells was significantly correlated with the allergen-specific serum IgE levels. When the allergic individuals were tested during the pollen season, the number of allergen-specific IL-4- and IL-13-producing cells, as well as serum levels of specific IgE, increased. The IL-13 increase seen in ELISPOT was confirmed by a RT-PCR assay. No seasonal changes were seen in response to purified protein derivative (PPD) or the mitogen PHA. During the pollen season, the IL-4 and IL-13 responses were highly correlated. Taken together, our results support the roles of both IL-13 and IL-4 in the regulation of allergen-specific IgE levels in atopic individuals.

Role of JAK3 in CD40-Mediated Signaling

CD40 is a member of the tumor necrosis factor receptor family and plays an important role in B-cell survival, growth, differentiation, and isotype switching. Recently, CD40 has been shown to associate with JAK3, a member of the family of Janus Kinases, which are nonreceptor protein kinases involved in intracellular signaling mediated by cytokines and growth factors. To investigate the role of JAK3 in CD40-mediated signaling, we studied the effect of CD40 stimulation on B-cell proliferation, IgE isotype switching, and upregulation of surface expression of CD23, ICAM-1, CD80, and LT-α in JAK3-deficient patients. Our studies show that stimulation of B cells with monoclonal antibody to CD40 in the presence of interleukin-4 (IL-4) or IL-13 resulted in similar responses in JAK3-deficient patients and normal controls. This suggests that JAK3 is not essential for CD40-mediated B-cell proliferation, isotype switching, and upregulation of CD23, ICAM-1, CD80, and LT-α surface expression.

Role of JAK3 in CD40-Mediated Signaling

CD40 is a member of the tumor necrosis factor receptor family and plays an important role in B-cell survival, growth, differentiation, and isotype switching. Recently, CD40 has been shown to associate with JAK3, a member of the family of Janus Kinases, which are nonreceptor protein kinases involved in intracellular signaling mediated by cytokines and growth factors. To investigate the role of JAK3 in CD40-mediated signaling, we studied the effect of CD40 stimulation on B-cell proliferation, IgE isotype switching, and upregulation of surface expression of CD23, ICAM-1, CD80, and LT-α in JAK3-deficient patients. Our studies show that stimulation of B cells with monoclonal antibody to CD40 in the presence of interleukin-4 (IL-4) or IL-13 resulted in similar responses in JAK3-deficient patients and normal controls. This suggests that JAK3 is not essential for CD40-mediated B-cell proliferation, isotype switching, and upregulation of CD23, ICAM-1, CD80, and LT-α surface expression.

Retinoic Acid Inhibits CD40 + Interleukin-4–Mediated IgE Production In Vitro

To elucidate the role of retinoic acid (RA) in anti-CD40 + interleukin-4 (IL-4)–mediated B-cell activation, the effect of 10−12 to 10−6 mol/L RA was studied in anti-CD40 (1 μg/mL) + IL-4 (5 ng/mL)-mediated proliferation and Ig synthesis by human peripheral blood mononuclear cells (PBMC) and B cells in healthy donors. Anti-CD40 + IL-4–mediated proliferation of PBMC and B cells was inhibited by RA in a dose-dependent manner, with maximal inhibition of 62% ± 5% in PBMC and 55% ± 4.4% in B cells by all-trans RA, and 58% ± 6.7% and 51% ± 4.7%, respectively by 13-cis RA. IgE synthesis was even more markedly inhibited by RA starting at concentrations of >10−14mol/L for B cells and >10−10 mol/L for PBMC. Maximal inhibition of IgE production for B cells was at 10−8mol/L for all-trans RA (94% ± 1.8%) and 96% ± 3.2% for 13-cis RA. Low concentrations of RA inhibiting IgE synthesis (10−10 mol/L) affected neither B-cell proliferation nor the production of IgA, IgG, and IgM. Elucidation of the mechanism involved in this inhibition of IgE production shows that epsilon germline transcription is decreased by RA, whereas production of interferon-γ (IFN-γ) was not enhanced in the presence of RA. To differentiate whether the RA effect was mediated by RA receptors , β, and γ, the expression of the retinoic acid receptors (RAR) was examined by reverse transcriptase-polymerase chain reaction (RT-PCR). The data show that unstimulated human peripheral B cells express mRNA of the RA receptor , β, and γ. Using retinoids with different receptor binding specificity (CD336, CD437, CD2019, CD367), dose-dependent inhibition of IgE synthesis was shown by all four derivates, but was most marked by an RA binding the  receptor with high specificity. Taken together, this study shows that RA inhibits IgE production of anti-CD40 + IL-4–stimulated B cells in vitro.

© 1998 by The American Society of Hematology.

Retinoic Acid Inhibits CD40 + Interleukin-4–Mediated IgE Production In Vitro

To elucidate the role of retinoic acid (RA) in anti-CD40 + interleukin-4 (IL-4)–mediated B-cell activation, the effect of 10−12 to 10−6 mol/L RA was studied in anti-CD40 (1 μg/mL) + IL-4 (5 ng/mL)-mediated proliferation and Ig synthesis by human peripheral blood mononuclear cells (PBMC) and B cells in healthy donors. Anti-CD40 + IL-4–mediated proliferation of PBMC and B cells was inhibited by RA in a dose-dependent manner, with maximal inhibition of 62% ± 5% in PBMC and 55% ± 4.4% in B cells by all-trans RA, and 58% ± 6.7% and 51% ± 4.7%, respectively by 13-cis RA. IgE synthesis was even more markedly inhibited by RA starting at concentrations of >10−14mol/L for B cells and >10−10 mol/L for PBMC. Maximal inhibition of IgE production for B cells was at 10−8mol/L for all-trans RA (94% ± 1.8%) and 96% ± 3.2% for 13-cis RA. Low concentrations of RA inhibiting IgE synthesis (10−10 mol/L) affected neither B-cell proliferation nor the production of IgA, IgG, and IgM. Elucidation of the mechanism involved in this inhibition of IgE production shows that epsilon germline transcription is decreased by RA, whereas production of interferon-γ (IFN-γ) was not enhanced in the presence of RA. To differentiate whether the RA effect was mediated by RA receptors , β, and γ, the expression of the retinoic acid receptors (RAR) was examined by reverse transcriptase-polymerase chain reaction (RT-PCR). The data show that unstimulated human peripheral B cells express mRNA of the RA receptor , β, and γ. Using retinoids with different receptor binding specificity (CD336, CD437, CD2019, CD367), dose-dependent inhibition of IgE synthesis was shown by all four derivates, but was most marked by an RA binding the  receptor with high specificity. Taken together, this study shows that RA inhibits IgE production of anti-CD40 + IL-4–stimulated B cells in vitro.

© 1998 by The American Society of Hematology.

Lymphotoxin-alpha is an important autocrine factor for CD40 + interleukin-4-mediated B-cell activation in normal and atopic donors

Stimulation of human B cells with anti-CD40 + interleukin-4 (IL-4) results not only in proliferation and immunoglobulin E (IgE)-production, but also increased production of the cytokine lymphotoxin-alpha (LT-alpha) (formerly also known as tumour necrosis factor-beta (TNF-beta)). Here, we studied the role of LT-alpha (TNF-beta) in B cells following stimulation with anti-CD40 + IL-4 from normal versus atopic donors. Anti-CD40 + IL-4 stimulation of peripheral blood mononuclear cells (PBMC) from atopic donors resulted in enhanced production of soluble LT-alpha (TNF-beta) and increased membrane LT-alpha (TNF-beta) expression on the B cells compared with normal donors. Functional evaluation of LT-alpha (TNF-beta) in CD40 + IL-4-stimulated B cells shows that recombinant LT-alpha (TNF-beta) induces proliferation of B cells and enhances CD40 + IL-4-mediated B-cell proliferation and IgE synthesis in both normal and atopic donors in a dose-dependent manner. These findings were supported by semiquantitative analysis of epsilon-germline transcripts using reverse transcription-polymerase chain reaction (RT-PCR) showing increased epsilon-germline transcription in the presence of LT-alpha. Furthermore, addition of anti-LT-alpha (anti-TNF-beta) to CD40 + IL-4-stimulated B cells partially inhibited proliferation and IgE synthesis in a dose-dependent manner indicating a role of endogenous LT-alpha (TNF-beta) production by B cells during continued CD40 + IL-4 stimulation. These data suggest that LT-alpha (TNF-beta) plays a potentially significant role during B-cell proliferation and IgE synthesis. Moreover, LT-alpha (TNF-beta) production seems to be differentially regulated in B cells from normal and atopic donors.

Epicutaneous sensitization with protein antigen induces localized allergic dermatitis and hyperresponsiveness to methacholine after single exposure to aerosolized antigen in mice

Our understanding of the pathogenesis of atopic dermatitis (AD) and its relationship to asthma remains incomplete. Herein, we describe a murine model of epicutaneous (EC) sensitization to the protein allergen, chicken egg albumin, ovalbumin (OVA), which results in a rise in total and OVA-specific serum IgE and leads to the development of a dermatitis characterized by infiltration of CD3(+) T cells, eosinophils, and neutrophils and by local expression of mRNA for the cytokines IL-4, IL-5, and interferon-gamma. A single exposure of the EC sensitized mice to aerosolized OVA induced eosinophilia in the bronchoalveolar lavage fluid and airway hyperresponsiveness to intravenous methacholine as assessed by measurement of pulmonary dynamic compliance (Cdyn). These results suggest a possible role for EC exposure to antigen in atopic dermatitis and in the development of allergic asthma.

Genetics of food allergy

Genetics of human diseases has passed through three main historical phases: (1) studies of formal genetics aimed at investigating mechanisms of inheritance using Mendelian models in population, family and twin surveys; (2) studies of associations between HLA antigens and diseases; and (3) direct mapping of genes through candidate gene or random genomic search approach. Very few data in each of these three phases are available for food allergy and intolerance. They are mostly confined to formal genetics studies of allergy in general and to HLA association studies in celiac diseases. The main reason for paucity of data in this important area of investigation is represented by the heterogeneity of the clinical entities grouped under the label of food allergy at the level of: (1) the clinical phenotype, because of the many diseases and end-organs interested; (2) pathophysiological variables involved, since several immunological and non-immunological mechanisms can be invoked in different cases of food allergy and intolerance; and (3) the foods or their absorbed metabolites which induce symptoms. However, progress made in genetics of allergy can be in part extrapolated to the limited number of cases where an IgE-mediated mechanism has been demonstrated. The review of studies based on a more punctual definition of the allergic phenotype and of the candidate genes (regions) of allergy: (1) suggests that allergen recognition and specific IgE response, total IgE (and IgG4) polyclonal activation, up-regulation of inflammatory cells (mast cells and eosinophils mainly) and hyper-responsiveness of end-organs are possibly regulated by different genetic and environmental factors; and (2) calls particular attention on the following genomic regions: 5q31.1-33, 6p21.3, 11q13,14. Research on genetics of food allergy and intolerance is highly recommended because of its high prevalence and of the potential applicative value of results for preventive measures of dietary control in subjects at risk. Since `food allergy and intolerance' does not represent an useful phenotype for genetic studies because of its heterogeneity, adequate strategies of gene mapping should be designed in study groups selected for defined variables with a well established role in the pathogenesis of the different clinical expressions of this common condition.

Increased allergen-specific Th2 responses in vitro in atopic subjects receiving subclinical allergen challenge

The study aimed to determine whether inhalation of subclinical allergen doses-leads to a shift in the balance between T helper (Th) 1 and Th2 cells in asthmatic patients. Elevated IgE requires allergen-specific T cells producing cytokines such as interleukin (IL)-4 or IL-13. Interferon-gamma (IFN-gamma) produced by Th1 cells counteracts the effects of IL-4. In nature, allergic persons are often exposed to low levels of allergen, leading to hyperreactivity, but not to acute allergic reactions. In this study, nine allergic persons inhaled low doses of allergen or placebo in a double-blind manner over seven consecutive weekdays. During the study, the bronchial responsiveness to histamine challenge increased, but no subject exhibited asthmatic symptoms. Blood was drawn on days 0, 1, 4, and 9, and the number of IL-4- and IFN-gamma-producing cells was measured by enzyme-linked immunospot (ELISPOT) assay after in vitro stimulation with a low-dose phytohemagglutinin (PHA) mixed with the relevant allergen or with PHA alone. In three of the four subjects receiving allergen, the IL-4/IFN-gamma ratio increased during the time of the study. No increase was seen in the placebo group. No increase was seen in serum IgE levels in any of the groups. We conclude that a shift in the balance between Th1 and Th2 cells can be detected in subjects exposed to subclinical allergen doses.

Specific induction of interleukin-4-producing cells in response to in vitro allergen stimulation in atopic individuals

BACKGROUND AND OBJECTIVE

CD4+ T cells can be divided into two major subsets, T helper (TH)1 and TH2 cells. Interleukin-4 (IL-4) is produced by TH2 cells and induces switching of immunoglobulin (Ig) M/IgG to IgE. Interferon-gamma (IFNgamma) produced by TH1 cells counteracts the IgE-promoting effects of IL-4. In this study we wanted to investigate whether the number of IL-4-producing cells could be a direct measurement of allergen exposure in vitro, and whether this was correlated to the elevated serum IgE-levels seen in atopic persons.

METHODS

We compared the number of IL-4- and IFNgamma-producing cells using an enzyme-linked immunospot assay (ELISPOT) in response to allergens from birch and cat in peripheral mononuclear cells from atopic and healthy individuals.

RESULTS

In the two sensitized groups there was an increase in the number of IL-4-producing cells in response to the specific allergen which was not seen in the healthy group (1/20000 cells and 1/200000 cells, respectively, P < 0.001 for birch). In criss-cross experiments where birch-sensitized individuals were stimulated with cat allergen, no IL-4-producing cells were seen, indicating a high degree of specificity. In individual subjects, the elevated numbers of IL-4-producing cells were significantly correlated with their allergen-specific serum IgE levels. When allergen was combined with a suboptimal dose of PHA, there was a synergistic increase in the number of allergen-induced IL-4-producing cells (1/4000 cells) in the atopic donors, which was not seen with the number of IFNgamma-producing cells.

CONCLUSIONS

Allergen-specific IL-4 producing cells in a peripheral blood mononuclear cell (PBMC) culture can be detected by ELISPOT and the response can synergistically be enhanced by suboptimal concentrations of PHA.

Homodimerization of the human interleukin 4 receptor alpha chain induces Cepsilon germline transcripts in B cells in the absence of the interleukin 2 receptor gamma chain

The cytokines interleukin (IL)-4 and IL-13 play a critical role in inducing Cepsilon germline transcripts and IgE isotype switching in human B cells. The IL-4 receptor (IL-4R) in B cells is composed of two chains, the IL-4-binding IL-4Ralpha chain, which is shared with the IL-13R, and the IL-2Rgamma (gammac) chain, which is shared with IL-7R, IL-9R, and IL-15R. IL-4 induces Cepsilon germline transcripts and IgE isotype switching in B cells from patients with gammac chain deficiency. Induction of Cepsilon germline transcripts by IL-4 in B cells that lack the gammac chain may involve signaling via the IL-13R. Alternatively, the IL-4Ralpha chain may transduce intracellular signals that lead to Cepsilon gene transcription independently of its association with other chains. We show that ligand-induced homodimerization of chimeric surface receptors consisting of the extracellular and transmembrane domains of the erythropoietin receptor and of the intracellular domain of IL-4Ralpha induces Janus kinase 1 (Jak1) activation, STAT6 activation, and Cepsilon germline transcripts in human B cell line BJAB. Disruption of the Jak1-binding proline-rich Box1 region of IL-4Ralpha abolished signaling by this chimeric receptor. Furthermore, B cells transfected with a chimeric CD8alpha/IL-4Ralpha receptor, which is expressed on the cell surface as a homodimer, constitutively expressed Cepsilon germline transcripts. These results suggest that homodimerization of the IL-4Ralpha chain is sufficient to transduce Jak1-dependent intracellular signals that lead to IgE isotype switching.

Interleukin-4 receptor expression by human B cells: functional analysis with a human interleukin-4 toxin, DAB389IL-4

BACKGROUND

Studies of human IgE-secreting B cells have proven difficult because of the small size of this population. We have used an interleukin-4 (IL-4) fusion toxin to detect functionally IL-4 receptor (IL-4R) expression on B cells involved in IgE synthesis.

METHODS

In diphtheria toxin IL-4 (DAB389IL-4) the receptor-binding domain of diphtheria toxin has been replaced with human IL-4. DAB389IL-4 cytotoxicity depends on IL-4R binding and internalization.

RESULTS

Addition of DAB389IL-4 inhibited IgE synthesis induced by IL-4+ anti-CD40 monoclonal antibody or hydrocortisone. IgE inhibition resulted from DAB389IL-4 B-cell cytotoxicity because DAB389IL-4 inhibited IL-4-independent B-cell proliferation. Thus induction of human IgE synthesis involves IL-4R+ cells. In contrast, terminally differentiated, IgE-producing B cells no longer express functional IL-4R because DAB389IL-4 only modestly inhibited ongoing IgE synthesis by B cells from patients with hyper-IgE states and only minimally affected IL-4-induced IgE synthesis in normal B cells when the toxin was added at day 7. Pokeweed mitogen-induced IgM synthesis was sensitive to early but not to late addition of DAB389IL-4. Thus the loss of functional IL-4R immunoglobulin-secreting B cells is independent of isotype switching.

CONCLUSIONS

IgE-secreting B cells no longer express functional IL-4R. Therapies for allergic disease that target the IL-4R would not affect IgE-secreting B cells but may block the recruitment of B cells into the IgE-secreting pool. For optimal benefits this approach may be combined with therapies that target IL-4R-, IgE-secreting B cells.

Overview of equine pruritus

Pruritus is a common complaint associated with equine dermatoses. Self-mutilation results in alopecia, excoriations, scaling, and crusting; the aesthetic appearance of the horse is often ruined and the horse may be unfit for riding or showing. This article specifically addresses those pruritic dermatoses caused by allergies, including food allergy/intolerance, atopy and contact allergy, as well as by two ectoparasites, stick-tight fleas and rhabditic mange. The clinical signs, diagnostic tests, and treatment recommendations are discussed for each disorder. Insect hypersensitivity and pruritus associated with the other more common ectoparasites are covered in depth elsewhere in this issue.

Role of protein tyrosine kinases and phosphatases in isotype switching: crosslinking CD45 to CD40 inhibits IgE isotype switching in human B cells

Protein tyrosine kinases and protein tyrosine phosphatases play an important role in the transduction of signals via antigen receptors in T and B cells, and in CD40-dependent B-cell activation. To examine the role of tyrosine kinases and phosphatases in B-cell isotype switching, we examined the effects of the engagement of the transmembrane phosphatase CD45 on the synthesis of IgE induced by IL-4 and anti-CD40 monoclonal antibody (mAb). Crosslinking CD45 to CD40 using biotinylated mAbs and avidin strongly inhibited CD40-mediated IgE synthesis in IL-4-treated human B cells. CD40/CD45 crosslinking did not affect epsilon germline transcription in B cells stimulated with IL-4, but strongly inhibited induction of S mu/S epsilon switch recombination as detected by a nested primer polymerase chain reaction assay. The B-cell src-type tyrosine kinase lyn, which is activated following CD40 engagement, is a potential target for the effects of CD45 observed in our experiments, because CD45/CD40 crosslinking resulted in the inhibition of CD40-mediated lyn phosphorylation and activation. These results suggest an important role for protein tyrosine kinases and phosphatases in CD40-mediated induction of isotype switching to IgE.

Allergy. Is localized immunoglobulin E synthesis the problem?

Cell-cell interactions controlling immunoglobulin E synthesis could be important components of the feedback loops that are initiated by exposure to allergens.