Allergen-induced Th1 and Th2 cytokine secretion in relation to specific allergen sensitization and atopic symptoms in children

BACKGROUND: Allergic diseases are believed to be due to T helper (Th)2-like immunity to allergens in affected tissues, and immune responses to allergens are characterized by a cross-regulation between Th1 and Th2 cells. Atopic individuals may develop IgE antibodies to only one or more allergens. However, the mechanisms behind sensitization to a specific allergen, e.g. why an individual develops IgE to cat but not birch, are not known. Our aim was to study birch- and cat-induced Th1 and Th2 cytokine secretion in children who were sensitized to birch but not to cat, and vice versa. MATERIALS AND METHODS: The subjects in the study were 60 12-year-old children. Seventeen of the children were sensitized (skin prick test and circulating IgE positive) to birch but not cat, 13 were sensitized to cat but not birch, 11 were sensitized both to birch and cat, and 19 children were skin prick test and circulating IgE negative. Forty-six children had a history of atopic symptoms, and 42 of them had current symptoms. Peripheral blood mononuclear cells were separated from venous blood and stimulated with cat or birch allergen. The levels of IL-4, IL-5, IL-9, IL-10, IL-13 and IFN-gamma in the cell supernatants were analysed by ELISA. RESULTS: Sensitized children produced more of the Th2 cytokines IL-4, IL-5, IL-9 and IL-13 than non-sensitized atopic and non-atopic children in response to stimulation with the allergen they were sensitized to. High levels of the Th2 cytokines IL-4 and IL-5 and low levels of the anti-inflammatory cytokine IL-10 were associated with atopic symptoms, and high cat-induced IL-9 levels with asthma. CONCLUSIONS: The Th2 cytokines IL-4, IL-5, IL-9 and IL-13 were all commonly detected in sensitized children after stimulation with the specific, in contrast to an unrelated, allergen. Atopic symptoms were associated with increased levels of IL-4 and IL-5 and tended to be associated with low levels of IL-10, and asthma with high cat-induced IL-9 levels.     

Interferon-γ- and interleukin-4-targeted gene therapy for atopic allergic disease

Two cytokines, interferon-gamma (IFN-gamma) and interleukin-4 (IL-4), which play critical roles in the regulation of serum IgE level by directing the interplay of T helper (Th)1 and Th2 cells, were chosen as targets for gene therapy. Anti-allergic activity was evaluated by determining the serum IgE level, and the functional status of each helper T cell was monitored by the serum concentrations of IgG1 and IgG2a. Experimental animals (BALB/c mice) were divided into four groups: the control group; the ovalbumin (OVA) group; the IFN-gamma group; and the IL-4 group. The control group was injected with saline and the OVA group with OVA-alum. The IFN-gamma and IL-4 groups were treated with OVA-alum plus the cDNAs of mouse IFN-gamma and IL-4 in an expression vector. These treatments were applied intramuscularly on a monthly basis for 4 months. OVA-alum treatment significantly increased the serum IgE and IgG1 concentrations, but did not affect IgG2a. Concomitant treatments with the cDNA of IFN-gamma or IL-4 returned the serum IgE almost to the control level and significantly suppressed the OVA-induced increase of IgG1. IFN-gamma cDNA increased the serum IgG2a but IL-4 cDNA had no affect. These results suggest that IFN-gamma inhibited the OVA-induced IgE production by suppressing the Th2 pathway and by enhancing the Th1 pathway. Administration of IL-4 cDNA suppressed the OVA-induced enhancement of IgE production by inhibiting the Th2 pathway rather than by potentiating it.     

In vivo administration of IL-18 can induce IgE production through Th2 cytokine induction and up-regulation of CD40 ligand (CD154) expression on CD4+ T cells

IL-18 is considered to be a strong cofactor for CD4+ T helper 1 (Th1) cell induction. We have recently reported that IL-18 can induce IL-13 production in both NK cells and T cells in synergy with IL-2 but not IL-12, suggesting IL-18 can induce Th1 and Th2 cytokines when accompanied by the appropriate first signals for T cells. We have now found that IL-18 can act as a cofactor to induce IL-4, IL-10 and IL-13 as well as IFN-gamma production in T cells in the presence of anti-CD3 monoclonal antibodies (mAb). IL-18 can rapidly induce CD40 ligand (CD154) mRNA and surface expression on CD4+ but not CD8+ T cells. The administration of IL-18 alone in vivo significantly increased serum IgE levels in C57BL/6 (B6) and B6 IL-4 knockout mice. Furthermore, the administration of IL-18 plus IL-2 induced approximately 70-fold and 10-fold higher serum levels of IgE and IgG1 than seen in control B6 mice, respectively. IgE and IgG1 induction in B6 mice by administration of IL-18 plus IL-2 was eliminated by the pretreatment of mice with anti-CD4 or anti-CD154, but not anti-CD8 or anti-NK1.1 mAb. These results suggest that IL-18 can induce Th2 cytokines and CD154 expression, and can contribute to CD4+ T cell-dependent, IL-4-independent IgE production.     

T regulatory cells in allergy and health: a question of allergen specificity and balance

Anergy, tolerance and active suppression may not be independent events, but rather involve similar mechanisms and cell types in immune regulation. Induction of allergen-specific regulatory/suppressor T cells (T(Reg)) seems essential for the maintenance of a healthy immune response to allergens. Allergen-specific immunotherapy can induce specific T(Reg) cells that abolish allergen-induced proliferation of T helper 1 (Th1) and Th2 cells, as well as their cytokine production. T(Reg) cells utilize multiple suppressive mechanisms, interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) as secreted cytokines and CTLA-4, PD-1, mTGF-beta, mIL-10, TGF-betaR and IL-10R as surface molecules. An important aspect of T(Reg) cells is the regulation of antibody isotypes and suppression of proinflammatory cells. IL-10 and TGF-beta secreted by T(Reg) cells skew production of IgE towards the noninflammatory isotypes, IgG4 and IgA, respectively. Furthermore, T(Reg) cells may directly or indirectly suppress effector cells of allergic inflammation such as basophils and eosinophils. In conclusion, induction of antigen-specific T(Reg) cells may redirect an inappropriate immune response against allergen or autoantigens with the help of a broad range of suppressor mechanisms.     

Sublingual immunotherapy with Dermatophagoides monomeric allergoid down-regulates allergen-specific immunoglobulin E and increases both interferon-γ- and interleukin-10-production

BACKGROUND: The clinical efficacy and safety of sublingual immunotherapy (SLIT) for aeroallergens has been demonstrated in several trials, whereas the immunological changes induced by this treatment, which may account for the clinical improvement, are still unclear. OBJECTIVE: To investigate the effects of a successful SLIT on the in vitro allergen-driven T cell response and cytokine secretion as well as on the serum levels of chemokines and of IgE, IgG1 and IgG4 antibodies (Abs). MATERIALS AND METHODS: Twenty-five Dermatophagoides pteronyssinus (Dp)-sensitive patients with perennial rhinitic and/or rhinitic and asthmatic symptoms were randomized into two groups (13 untreated (UT) and 12 SLIT-treated) for a 1 year and half study. The proliferative response of peripheral blood mononuclear cell (PBMC) to purified Der p1 allergen, their cytokines (IFN-gamma, IL-4, IL-10 and TGF-beta) production and serum levels of chemokines associated with T helper type 1 (Th1) (CXCL10) or T helper type 2 (Th2) (CCL22) responses and of Dp-specific IgE, IgG1 and IgG4 Abs were evaluated before and after 6 months of treatment. RESULTS: SLIT induced a significant reduction of symptom medication scores after 6, 12 and 18 months of treatment in comparison with UT patients. SLIT-treated patients showed a significant decrease in serum levels of DP-specific IgE Abs, whereas total IgE, and specific IgG1 and IgG4 Abs remained unchanged. The proliferative response of allergen-specific T cells to Der p1 in vitro after 6 months of treatment was reduced, while no effect was observed on T cell proliferation to recall antigen (streptokinase). Moreover, Der p1-driven IFN-gamma and IL-10 were significantly increased in culture supernatants of PBMC from 6 month-treated patients in comparison with those detected at the beginning of therapy. CONCLUSIONS: These data suggest that the allergen-driven enhancement of IL-10- and IFN-gamma-producing T cells precedes and associates with SLIT-induced down-regulation of specific IgE, thus providing a rationale to explain the clinical benefit of SLIT in allergic patients.     

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 1L-13. Interferon-gamma (IFN-y) produced by Till 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-γ-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-y 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 Thl and Th2 cells can be detected in subjects exposed to subclinical allergen doses.     

Analysis of recombinant mycobacteria as T helper type 1 vaccines in an allergy challenge model

The potential for development of mycobacteria as T helper type 1 (Th1) vaccines capable of induction of Th1 responses to recombinant antigens was explored in a model system based on an immunodominant peptide from house dust mite. Different recombinant mycobacterial preparations were compared for their ability to induce a Th1 response to the peptidea. It was found that mycobacterial viability was not a prerequisite for Th1 immunogenicity. A dominant interferon-gamma (IFN-gamma) response to peptide was observed in splenocytes from C57BL/6J mice immunized with live or heat-killed preparations of recombinant Mycobacterium vaccae or with live attenuated bacillus Calmette-Guèrin (BCG) vaccine expressing the antigen. Interleukin-5 (IL-5), a marker of a Th2 response, was detected only in mice receiving live M. vaccae. A similar pattern was observed in BALB/b mice, although the magnitude of the IFN-gamma response was much lower. Control and immunized mice were subsequently exposed to allergen using a Th2-inducing challenge protocol. A significant shift from a Th2 to a Th1 response was observed in immunized mice, as judged by cytokine expression by splenocytes and by subclass of circulating antibody. The effect was seen in three inbred mouse strains differing in their innate bias towards Th1 or Th2 responses. It was dependent on the presence of specific antigen in the mycobacterial preparation and, under the immunization conditions tested, was more pronounced with dead M. vaccae than with live BCG as carrier vaccine. The results demonstrate the potency of killed mycobacteria as Th1 adjuvants and suggest a potential application for recombinant mycobacteria in antigen-specific immune modulation.     

Inhibition of T helper 2-type responses, IgE production and eosinophilia by synthetic lipopeptides

In allergy and asthma, the fine balance between the T helper (Th) 1, Th2 and T regulatory cytokine responses appears to be shifted towards Th2. Here, we report that synthetic lipopeptides which contain the typical lipid part of the lipoprotein of gram-negative bacteria stimulate a distinct regulatory cytokine pattern and inhibit several Th2 cell-related phenomena. The most potent analogue of synthetic lipopeptides, lipopeptide CGP 40774 (LP40) was not active in MyD88-deficient mice and stimulated Toll-like receptor (TLR)-2, but not TLR-4. LP40 potentiated the production of IFN-gamma and IL-10, but not IL-4 and IL-5 by human T cells. In addition, triggering of TLR-2 by lipopeptides promoted the in vitro differentiation of naive T cells towards IL-10- and IFN-gamma-producing T cells and suppressed IL-4 production by Th2 cells. Accordingly, LP40 inhibited IgE production induced by allergen, anti-IgD antibody, Nippostrongylus brasiliensis or murine acquired immunodeficiency virus. Furthermore, ovalbumin-induced lung eosinophilic inflammation was abolished and Schistosoma mansoni egg-induced granuloma size and eosinophil counts were suppressed in mice by LP40. These results demonstrate that stimulation of TLR-2 by lipopeptides represents a novel way for possible treatment of allergy and asthma by regulating the disrupted cytokine balance.     

Elimination of IgE regulatory rat CD8+ T cells in vivo increases the co-ordinate expression of Th2 cytokines IL-4, IL-5 and IL-10.

Immunization of rats with soluble antigen (ovalbumin) and the castor bean toxin, ricin, eliminates a subpopulation of CD8+ T cells which suppress IgE responses in vivo. This treatment also reduces the ability of splenic T cells to produce interferon-gamma (IFN-gamma) and enhances their capacity to make interleukin-4 (IL-4). In this report we describe the effect of immunization with ricin and antigen on the expression of mRNA for other T-helper type 2 (Th2) cytokines--IL-5 and IL-10--and their relationship to serum IgE and IL-4 mRNA expression. Splenocytes were taken from rats at different times after immunization with antigen or ricin and antigen and activated in vitro with phorbol myristate acetate (PMA) and ionomycin for 6 hr and total RNA extracted and reverse transcribed. Cytokine gene expression was detected using a quantitative polymerase chain reaction (PCR). Expression of IL-4, IL-5, and IL-10 was increased 7-20-fold 11 days after immunization with ricin and antigen (from 0.107% to 0.769% beta-actin for IL-4, from 0.0167% to 0.381% beta-actin for IL-5, and from 0.0581% to 0.954% beta-actin for IL-10), and preceded maximum serum IgE levels by 4-5 days. There was no increase in IgE or mRNA for these cytokines in rats immunized with antigen alone. The level of IL-4, IL-5, and IL-10 expression declined rapidly after 12 days. Our results suggest that immunization with antigen and ricin preferentially induces a Th2 response, and that CD8+ T cells may play a part in down-regulating the development of Th2 T cells.     

Human Th1 and Th2 lymphocytes: their role in the pathophysiology of atopy

In human beings, as in mice, two distinct patterns of cytokine secretion have been defined among CD4+ helper T-cell clones. Human type 1 helper (Th1), but not type 2 helper (Th2), cells produce interleukin-2 (IL-2), gamma-interferon (IFN-gamma), and tumor necrosis factor-beta, whereas Th2, but not Th1, cells secrete IL-4 and IL-5, but not IL-2 or IFN-gamma. Other cytokines, such as IL-3, IL-6, GM-CSF, or TNF-alpha, are produced by both Th1 and Th2 cells. Th0 cells, a third Th subset, show combined production of Th1- and Th2-type cytokines. The different cytokine patterns are associated with different functions. In general, Th2 cells provide an excellent helper function for B-cell antibody production, particularly of the IgE class. On the other hand, Th1 cells are responsible for delayed type hypersensitivity reactions and are cytolytic for autologous antigen-presenting cells, including B cells. Most allergen- or helminth-antigen-specific human CD4+ T-cell clones exhibit a Th2 phenotype, whereas most clones specific for bacterial antigens show a Th1 profile. Allergen-specific Th2 cells seem to play a crucial role in atopy. These cells induce IgE production via IL-4 and favor the proliferation, differentiation, and activation of eosinophils via IL-5. In addition, Th2-derived IL-3 and IL-4 are mast-cell growth factors that act in synergy, at least in vitro. Recent evidence indicates that allergen-specific Th2 cells are selectively enriched in tissues affected by allergic inflammation, such as the bronchial mucosa of subjects with allergic asthma.(ABSTRACT TRUNCATED AT 250 WORDS)     

Administration of interleukin-12 exerts a therapeutic instead of a long-term preventive effect on mite Der p I allergen-induced animal model of airway inflammation

Interleukin-12 (IL-12) is a key cytokine, which promotes T helper type 1 (Th1) cell-mediated immunity and inhibits Th2-type responses. It has been previously shown that IL-12 administration during active immunization following a single allergen exposure can prevent antigen-induced increases in immunoglobulin E (IgE) formation, Th2 cytokine production and bronchoalveolar lavage (BAL) eosinophils in a murine model of allergic airway inflammation. Thus, these studies have now been extended and two IL-12 treatment protocols on this murine model were evaluated. Administration of IL-12 during the active immunization strikingly increased Der p I-specific serum IgG2a and transiently decreased the levels of IgG1 and IgE antibodies following multiple allergen challenges. Such early treatment of IL-12 down-regulated IL-5 production and modestly up-regulated interferon-gamma production but did not effect BAL eosinophilia. These results suggest that repeated exposure to antigen and IL-12 is necessary to maintain a persistent Th1-recall response. Furthermore, administration of IL-12 to actively immunized mice, in which Th2-associated responses were established, had a significant effect on IgG2a synthesis and a modest effect on IgE levels, also down-regulation of IL-5 production, and markedly increased interferon-gamma production and abolished recruitment of eosinophils. Therefore, these data indicate that IL-12 can inhibit antigen-induced eosinophil infiltration into airways, despite the existence of a Th2-associated response. Taken together, these studies suggest that IL-12 may be useful as an immunotherapeutic agent in the treatment of such pulmonary allergic disorders as bronchial asthma.     

A double-blind placebo-controlled birch allergy vaccination study II: correlation between inhibition of IgE binding, histamine release and facilitated allergen presentation

Background The pathogenesis of IgE‐mediated allergic disease is closely related to the production of T‐helper type 2 (Th2) cytokines, which lead to IgE production pivotal for activation of mast cells and basophils. Proliferating T cells along with eosinophils expanded and attracted by Th2 cytokines are major contributors to the late‐phase reaction. The activation of these Th2 cells is strongly enhanced by CD23‐mediated IgE facilitated allergen presentation (FAP). Objective The present study aims to investigate the effect of specific immunotherapy (SIT)‐induced allergen‐specific non‐IgE antibodies (blocking antibodies) on IgE binding to allergen, histamine release (HR) and CD23‐mediated allergen uptake in antigen‐presenting cells. Methods Competition between IgE and non‐IgE for allergen binding was studied by Advia Centaur antibody measurements, passively sensitized basophils were used to study HR and IgE‐facilitated binding of allergen to B cells (FAP) was studied by flow cytometry. FAP measurements were performed both with and without the addition of a reference IgE serum, which was included to obtain optimal complex formation. The serum samples were obtained from birch pollen immunotherapy (n=21) or placebo control patients (n=21) before and after 1 and 2 years of treatment. Results Statistically significant reduction of all parameters investigated was observed after 1 year of treatment and the effect was maintained during the second year of treatment. There was a clear correlation between the two FAP measurements and between each of them and the level of T cell activation reported upon previously. Moreover, strong correlations were found between changes in FAP, IgE binding and HR. Conclusion The present study clearly demonstrates that SIT induces changes in the composition of serum antibodies that inhibit IgE binding, HR and FAP to a similar extent. This suggests that these measurements, individually or in combination, may be used to monitor the immunological effect of SIT, even though direct correlations to changes in clinical parameters could not be demonstrated.     

Suppression of allergic airway inflammation and IgE responses by a class I restricted allergen peptide vaccine

CD8 T cells are known to deviate CD4 T-cell responses from Th2 toward Th1. Reduction of Th2 cytokines and increased interferon-γ ameliorates allergic airway disease. We have developed a novel approach to the suppression of allergic airway inflammation, by designing a MHC class I-restricted allergen peptide vaccine, which induces potent and long-lived CD8 T-cell responses. Vaccination of C57BL/6 mice before allergen sensitization completely prevented allergen-specific immunoglobulin E (IgE) antibody responses. Vaccination after sensitization failed to suppress IgE, but inhibited accumulation of eosinophils and neutrophils in airways after subsequent allergen challenge. Vaccination suppressed Th2 airway infiltration and enhanced the lung Th1 response without inducing excessive CD8 cellular infiltration or interleukin-17, and the combination of class I peptide with adjuvant was more effective than adjuvant alone. Airway hyperreactivity was prevented by vaccination in an allergen-specific fashion. Class I peptide vaccines might therefore represent a robust and long-lasting immunotherapeutic strategy in allergic disease.     

Inverse relationship between neopterin and immunoglobulin E

Polarized human T helper (Th) cells play a key role in the network of the specific immune system compartments. Cell-mediated immune response depends on activation of Th1-type cells, typically producing and releasing interferon-gamma and interleukin-2, whereas activation of Th2-type cells and production of cytokines such as interleukin-4, -5, and -10 are involved in humoral immune response and the production of immunoglobulins. Increased amounts of neopterin are produced during the Th1-type immune response by human monocytes/macrophages upon stimulation with the Th1-derived cytokine interferon-gamma, and thus the determination of neopterin concentrations allows us to monitor Th1-type immune response. We compared serum concentrations of neopterin with immunoglobulin E (IgE), a typical product of the Th2-type immune response, in order to examine the relationship between Th1-type and Th2-type immune system stimulation in 709 healthy outpatients, who visited the physician's office for a medical health checkup. Eleven percent presented with serum neopterin concentrations >8.7 nmol/L; 26% had increased serum concentrations of IgE (>100 kIU/L). There existed an inverse correlation between serum neopterin and IgE concentrations (Spearman's rank correlation coefficient: r(s) = -0.100; P < 0.01) which was stronger when excluding data < or = 8.7 nmol/L neopterin and < or = 100 kIU/L IgE (n = 246; r(s) = -0.519; P < 0.0001). Data indicate that increased serum neopterin concentrations are associated with low serum IgE and increased serum IgE with low serum neopterin concentrations. This finding fully agrees with the current understanding that in humans the activation of Th1 and Th2 cell-mediated immune responses are down-regulating each other.     

Differential regulation of allergen-specific antibodies in allergy and specific immunotherapy

Allergen-specific immunotherapy (SIT) aims to specifically skew an allergic response into a normal immune reaction against an allergen. The response to bee venom (BV) provides an especially suited model to study the immunological mechanisms of SIT in human. The BV-phospholipase A2 (PLA) represents the major antigen/allergen of BV. In SIT of BV allergy both whole BV and T cell epitope peptides of PLA were successfully applied. It appeared that the induction of specific anergy in peripheral T cells and reactivation of the T cells by microenvironmental cytokines represent the basic key steps in the immunological mechanism of SIT. The proliferative and cytokine responses by specific T cells were significantly suppressed simultaneously with an increase in IL-10 after 7 days. The anergic state was fully established after 4 weeks. Neutralization of IL-10 in PBMC by a specific antibody reconstituted the original proliferative and cytokine responses. Intracytoplasmatic cytokine staining revealed that IL-10 was initially produced by activated allergen-specific T cells. IL-10-producing B cells and monocytes were involved at a later stage of SIT and in maintenance of the anergy. The addition of IL-10 to stimulated PBMC or purified B cells inhibited IgE synthesis and enhanced the IgG4 antibody formation. Thus, SIT generates IL-10, which in turn induces specific anergy by autokrine interaction in T cells and counter-regulates IgE and IgG4 production. Particular cytokines from the tissue microenvironment reactivate the T cells to produce distinct Th1 or Th2 cytokine patterns respectively and by this way direct SIT towards successful or unsuccessful treatment. High amounts of allergen administered in SIT preferentially generate Th1 cytokines in T cells and IgG4 antibodies in memory B cells. Further investigations demonstrated that suppression of T cells by IL-10 is an active process, which depends on the expression and participation of CD28.     

Cytomegalovirus M43 gene modulates T helper cell response

Role of viral genes in modulating T helper 1 (Th1) and T helper 2 (Th2) balance is of principal interest in the study of cytomegalovirus (CMV) immunity. Murine CMV (MCMV) mutants were used to explore a possible mechanism for the ability of virus to induce a predominant Th1 response and to suppress Th2 response by examining the production of Th1 (IFN-gamma, IL-2) and Th2 (IL-4, IL-10) cytokines by the splenocytes of mice infected with wild type (WT) and MCMV mutants. Results (n=6) show that as compared with WT, the MCMV mutant with specific disruption of M43 gene upregulates the production of IL-4 (P=0.0002) and to a lesser extent IL-10 (P=0.015) at 14 days post infection. This indicates that M43 gene may play a role in suppressing Th2 (IL-4) production, especially in the later stage of infection. The IL-4 and IL-10 production during infection with M43 mutant occurs in the presence of a strong IFN-gamma (Th1) response, overriding the cross-regulatory effects of these cytokines within the Th1/Th2 paradigm and suggesting that the predominant response during CMV infection is still a Th1 type response.     

Exogenous type-1 cytokines modulate mercury-induced hyper-IgE in the rat

Suppression of IgE responses is a major goal for immunotherapy, especially in the field of allergy. The Th2 subset of helper T cells plays a vital role in class switching of B cells to IgE production by releasing IL-4. In susceptible rat strains, mercuric chloride (HgCl2) induces activation of Th2 cells, with enhanced expression of IL-4, polyclonal B cell activation and very high levels of circulating IgE. We have previously shown that spontaneous regulation of this response coincides with enhanced expression of Th1/type-1 cytokines, including interferon-gamma (IFN-gamma) and IL-12. We now report the effects of administration of exogenous type-1 cytokines on HgCl2-induced Th2 responses. At high doses, recombinant rat IFN-gamma markedly reduced serum IgE levels. Recombinant mouse IL-12 was less effective at suppressing the IgE response following HgCl2, although it caused marked up-regulation of IFN-gamma gene expression in the spleen. In Lewis rats, which are resistant to HgCl2-induced autoimmunity, a rise in serum IFN-gamma was observed after HgCl2, but administration of polyclonal anti-IFN-gamma antibodies did not render them susceptible to induction of a Th2 response by HgCl2. Our data show that individual type-1 cytokines are capable of suppressing the dramatic Th2 response induced by HgCl2 in the rat, even when they are not given until after starting HgCl2 administration. IFN-gamma is a pivotal cytokine in ameliorating the Th2 response and measures aimed at selective up-regulation of this cytokine may be of therapeutic value in suppression of unwanted IgE responses.     

Interleukin-10-treated dendritic cells do not inhibit Th2 immune responses in ovalbumin/alum-sensitized mice

BACKGROUND: It is well known that the immunoregulatory cytokine interleukin (IL)-10 inhibits the accessory function of human dendritic cells (DC) in vitro. Recently, we have shown that these IL-10 DC inhibit the production of T helper cell 1 (Th1) and T helper cell 2 (Th2) cytokines by T cells from atopic individuals in vitro. The current study was set out to analyze whether IL-10 DC also exert inhibitory effects in vivo in a murine model of allergy to ovalbumin adsorbed to the adjuvant aluminium hydroxide (OVA/alum). METHODS: OVA-pulsed or unpulsed bone marrow-derived DC, treated with IL-10 or left untreated during generation, were injected intravenously into BALB/c mice prior to and during OVA/alum sensitization, and sera and immune responses of mesenterial lymph node cells were analyzed. Additionally, bronchoalveolar lavage was performed after intranasal challenge with OVA. RESULTS: Treatment of BALB/c mice with OVA-pulsed DC led to a significantly enhanced proliferation as well as Th2 (IL-4, IL-5), Th1 (interferon-gamma) and IL-10 cytokine production after restimulation of lymph node cells with OVA in vitro compared with OVA immunization alone. In contrast, using OVA-pulsed IL-10 DC for transfer, proliferation and cytokine production by lymph node cells were not enhanced. OVA-specific immunoglobulin G1 (IgG1) and IgG2a production were significantly increased after transfer of OVA-pulsed DC and OVA-pulsed IL-10 DC, respectively, whereas anti-OVA IgE production and airway eosinophilia remained unchanged. CONCLUSIONS: Our data indicate that IL-10 treatment of DC decreases the Th1 and Th2 stimulatory capacity of DC but does not actually inhibit systemic (IgE) and local (airway inflammation) allergen-specific immune responses in a murine model of allergy.