Glucocorticoids increase the synthesis of immunoglobulin E by interleukin 4-stimulated human lymphocytes

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.

Hydrocortisone enhances allergen-specific IgE production by peripheral blood mononuclear cells from atopic patients with high serum allergen-specific IgE levels

BACKGROUND

Although there is convincing evidence that human B cells can be induced to produce IgE by a combination of interleukin 4 (IL-4) and hydrocortisone (HC) in atopic subjects, it is still uncertain if this performs the same functions in allergen-specific IgE synthesis.

OBJECTIVE

This study was designed to investigate the differences of IgE regulation between atopics and nonatopics, interactions of HC with IL-4, and the correlation between in vitro total IgE, allergen-specific IgE synthesis and serum IgE levels.

METHODS

Peripheral blood mononuclear cells (PBMCs) from 16 atopic asthma patients sensitive to Dermatophagoides farinae and seven nonatopic controls were cultured with IL-4 and/or HC. Total IgE and D. farinae-specific IgE in culture supernatant were measured by ELISA and FAST.

RESULTS

IL-4 increased total IgE synthesis in PBMCs from both atopics and nonatopics, whereas, HC had this effect only in some atopics who showed spontaneous IgE production in vitro. HC acted synergistically with IL-4 in total IgE synthesis. Their effects were more remarkable in cases with lower total serum IgE levels. PBMCs from eight of 16 atopics produced D. farinae-specific IgE in vitro either spontaneously or by IL-4 and/or HC. HC had more profound effects than IL-4 in these patients. They also showed higher total IgE synthesis by HC, and higher specific serum IgE levels than the others. IL-4 and/or HC did not induce any D. farinae-specific IgE synthesis by PBMCs from nonatopics.

CONCLUSION

HC had a more profound effect than IL-4 on the induction of D. farinae-specific IgE synthesis in atopic patients with high serum allergen specific IgE levels. Further studies to determine the causes of these effects, such as the presence of long lived allergen specific B cells as the result of the priming effect of IL-4 in vivo, may be needed.

Mechanism of topical glucocorticoid treatment of hay fever: IL-5 and eosinophil activation during natural allergen exposure are suppressed, but IL-4, IL-6, and IgE antibody production are unaffected

BACKGROUND

Allergic rhinitis is traditionally defined as an IgE- and mast cell-mediated hypersensitivity reaction. Allergen challenge models suggest that cytokines and eosinophil mediators may also play roles. However, the causal relationship among inflammatory cells, their products, and patients' symptoms during natural allergen exposure has not been established.

OBJECTIVE

We sought to elucidate the mechanisms of seasonal allergic rhinitis and the beneficial effects of topical glucocorticoids.

METHODS

Thirty patients with ragweed-induced hay fever and a strongly positive serologic test response for ragweed IgE antibody received budesonide nasal spray or placebo in a randomized, parallel, double-blind study. Nasal wash fluids and sera were collected before and during the hay fever season. The levels of inflammatory mediators and allergen-specific immunoglobulins were measured by immunoassay. The activation markers on blood eosinophils were quantitated by flow cytometry.

RESULTS

Compared with placebo-treated patients, budesonide-treated patients had strikingly reduced symptoms. In the placebo group, nasal symptoms correlated with nasal lavage fluid eosinophil-derived neurotoxin and IL-5 levels. At the season peak, the budesonide-treated group had significantly lower nasal fluid eosinophil-derived neurotoxin, IL-5, and soluble intracellular adhesion molecule-1 levels. In the treated group eosinophil expression of CD11b was suppressed at the season peak. In contrast, levels of IL-4 and IL-6 in nasal fluid and the seasonal increases in serum ragweed-specific IgE and nasal fluid IgA antibodies did not differ between groups.

CONCLUSION

Eosinophilic inflammation plays a critical role in seasonal allergic rhinitis symptoms. One of the therapeutic effects of glucocorticoids is to suppress this inflammation.

Glucocorticoids in T cell development and function*

Glucocorticoids are small lipophilic compounds that mediate their many biological effects by binding an intracellular receptor (GR) that, in turn, translocates to the nucleus and directly or indirectly regulates gene transcription. Perhaps the most recognized biologic effect of glucocorticoids on peripheral T cells is immunosuppression, which is due to inhibition of expression of a wide variety of activationinduced gene products. Glucocorticoids have also been implicated in Th lineage development (favoring the generation of Th2 cells) and, by virtue of their downregulation of fasL expression, the inhibition of activation-induced T cell apoptosis. Glucocorticoids are also potent inducers of apoptosis, and even glucocorticoid concentrations achieved during a stress response can cause the death of CD4(+)CD8(+ )thymocytes. Perhaps surprisingly, thymic epithelial cells produce glucocorticoids, and based upon in vitro and in vivo studies of T cell development it has been proposed that these locally produced glucocorticoids participate in antigen-specific thymocyte development by inhibiting activation-induced gene transcription and thus increasing the TCR signaling thresholds required to promote positive and negative selection. It is anticipated that studies in animals with tissue-specific GR-deficiency will further elucide how glucocorticoids affect T cell development and function.

Inhibition of Th1 immune response by glucocorticoids: dexamethasone selectively inhibits IL-12-induced Stat4 phosphorylation in T lymphocytes

Glucocorticoids are widely used in the therapy of inflammatory, autoimmune, and allergic diseases. As the end-effectors of the hypothalamic-pituitary-adrenal axis, endogenous glucocorticoids also play an important role in suppressing innate and cellular immune responses. Previous studies have indicated that glucocorticoids inhibit Th1 and enhance Th2 cytokine secretion. IL-12 promotes Th1 cell-mediated immunity, while IL-4 stimulates Th2 humoral-mediated immunity. Here, we examined the regulatory effect of glucocorticoids on key elements of IL-12 and IL-4 signaling. We first investigated the effect of dexamethasone on IL-12-inducible genes and showed that dexamethasone inhibited IL-12-induced IFN-gamma secretion and IFN regulatory factor-1 expression in both NK and T cells. This occurred even though the level of expression of IL-12 receptors and IL-12-induced Janus kinase phosphorylation remained unaltered. However, dexamethasone markedly inhibited IL-12-induced phosphorylation of Stat4 without altering its expression. This was specific, as IL-4-induced Stat6 phosphorylation was not affected, and mediated by the glucocorticoid receptor, as it was antagonized by the glucocorticoid receptor antagonist RU486. Moreover, transfection experiments showed that dexamethasone reduced responsiveness to IL-12 through the inhibition of Stat4-dependent IFN regulatory factor-1 promoter activity. We conclude that blocking IL-12-induced Stat4 phosphorylation, without altering IL-4-induced Stat6 phosphorylation, appears to be a new suppressive action of glucocorticoids on the Th1 cellular immune response and may help explain the glucocorticoid-induced shift toward the Th2 humoral immune response.

In vitro IgE inhibition in B cells by anti-CD23 monoclonal antibodies is functionally dependent on the immunoglobulin Fc domain

CD23, the low affinity receptor for IgE (FcvarepsilonRII), is involved in regulation of IgE synthesis by B-lymphocytes. Five monoclonal antibodies to human CD23 were generated from cynomolgus macaques immunized with purified soluble CD23 (sCD23). Four of the five primate antibodies blocked the binding of IgE complexes to CD23 positive cells and also inhibited the production of IgE in vitro by IL-4 induced human peripheral blood mononuclear cells (PBMC). The variable domains of several primate antibodies were utilized to construct chimeric macaque/human (PRIMATIZED((R))) monoclonal antibodies. PRIMATIZED((R)) p5E8G1, containing human gamma 1 constant region, inhibited IgE production in vitro as efficiently as the parent primate antibody, but the human gamma 4 constant version, PRIMATIZED((R)) p5E8G4, was not as effective in IgE inhibition. An F(ab')(2) of p5E8G1 did not inhibit IgE production but did interfere with IgE inhibition by the intact anti-CD23 antibody in a dose dependent fashion. The murine monoclonal antibody MHM6 recognizes human CD23 at a different epitope than primate antibody 5E8, and inhibits IgE production by IL-4 induced PBMC. As with the F(ab')(2) of p5E8G1, the F(ab')(2) of MHM6 also failed to inhibit IgE production. These data imply that the mechanism by which anti-CD23 antibodies inhibit IgE production requires cross-linking of CD23 to an IgG receptor. These data also imply that neither bivalent cross-linking of CD23 alone or inhibition of CD23 binding to its natural ligands is sufficient to inhibit IgE production.

How do glucocorticoids influence stress responses? Integrating permissive, suppressive, stimulatory, and preparative actions

The secretion of glucocorticoids (GCs) is a classic endocrine response to stress. Despite that, it remains controversial as to what purpose GCs serve at such times. One view, stretching back to the time of Hans Selye, posits that GCs help mediate the ongoing or pending stress response, either via basal levels of GCs permitting other facets of the stress response to emerge efficaciously, and/or by stress levels of GCs actively stimulating the stress response. In contrast, a revisionist viewpoint posits that GCs suppress the stress response, preventing it from being pathologically overactivated. In this review, we consider recent findings regarding GC action and, based on them, generate criteria for determining whether a particular GC action permits, stimulates, or suppresses an ongoing stress-response or, as an additional category, is preparative for a subsequent stressor. We apply these GC actions to the realms of cardiovascular function, fluid volume and hemorrhage, immunity and inflammation, metabolism, neurobiology, and reproductive physiology. We find that GC actions fall into markedly different categories, depending on the physiological endpoint in question, with evidence for mediating effects in some cases, and suppressive or preparative in others. We then attempt to assimilate these heterogeneous GC actions into a physiological whole.

Glucocorticoids and immune function

The prevailing notion has been that cytokines such as interleukin-1 released from sites of inflammation cross the blood-brain barrier and drive the hypothalamo-pituitary-adrenal (HPA) axis so that cortisol is released into the circulation to exert indiscriminate systemic anti-inflammatory effects. It is now clear that feedback from the HPA axis is subject to more subtle and localized regulation. The signal that activates cortisol release travels to the hypothalamus via vagal sensory afferents (so the brain 'knows' where the inflammation is), and the effects of the released cortisol are regulated within individual tissues via numerous mechanisms, including changes in the affinity of the cortisol receptors, and changes in the equilibrium point of the cortisol/cortisone shuttle (11 beta hydroxysteroid dehydrogenases 1 and 2). This equilibrium is locally regulated by cytokines. These mechanisms are central to the regulation of the balance of Th1 to Th2 cytokines within sites of inflammation, and to the appropriate or inappropriate termination of the inflammatory response in infections or autoimmunity.

Cortisol metabolism, cortisol sensitivity and the pathogenesis of leprosy reactions

The concentration of cortisol in a tissue is regulated by a reversible enzyme 'shuttle' that can deactivate cortisol by converting it to cortisone, or activate cortisone by converting it to cortisol. The activity of this shuttle, and the direction in which it operates, is regulated by numerous factors including cytokines. This results in large swings in the effective cortisol concentration in sites of inflammation at different phases of an inflammatory response. Thus changes in local cortisol concentration can be largely independent of circulating cortisol levels. The relevant shuttle enzymes are present in skin, blood vessels and nervous tissue, and inhibition of the enzymes in skin enhances the local anti-inflammatory effect of cortisol. We therefore suggest that changes in the activity or direction of action of the shuttle in leprosy lesions may predispose to reactions, requiring exogenous steroid supplements to regain control of the inflammation.

IgE Hyperproduction Through Enhanced Tyrosine Phosphorylation of Janus Kinase 3 in NC/Nga Mice, a Model for Human Atopic Dermatitis

IgE hyperproduction frequently observed in patients with atopic dermatitis (AD) may greatly contribute to the pathogenesis of AD, but its mechanisms are still unclear. NC/Nga mice raised in nonsterile circumstances spontaneously suffered from AD-like skin lesions with elevation of plasma IgE levels. We investigated mechanisms of the IgE hyperproduction in NC/Nga mice. Splenic T cells from SPF NC/Nga mice had a level of CD40 ligand (CD40L) expression comparable to that of BALB/c mice. Although there was no difference in the expression of CD40 on B cells between NC/Nga and BALB/c mice, B cells of NC/Nga mice produced much more IgE in the presence of soluble CD40L and IL-4. The stimulation with CD40L and/or IL-4 resulted in tyrosine phosphorylation of Janus kinase 3 (JAK3) in B cells, which was more strongly inducible in NC/Nga mice than in BALB/c mice. In B cells isolated from PBMC of AD patients with high serum IgE levels, JAK3 was constitutively phosphorylated at the tyrosine residue, and its phosphorylation was enhanced by the treatment with CD40L and/or IL-4 as was that in splenic B cells of NC/Nga mice with dermatitis and high IgE levels. Thus, it is suggested that constitutive and enhanced JAK3 phosphorylation in B cells highly sensitive to CD40L and IL-4 may be attributable to IgE hyperproduction in NC/Nga mice and patients with AD.

Inhibitors of the p38 Mitogen-Activated Kinase Modulate IL-4 Induction of Low Affinity IgE Receptor (CD23) in Human Monocytes

CD23, the low affinity IgE receptor, is up-regulated on the surface of IL-4-treated B cells and monocytes and is immediately proteolytically processed, releasing soluble fragments of CD23. Here, we report that inhibitors of the p38 mitogen-activated kinase (p38 MAPK), SK&F 86002 or the more selective inhibitor, SB 203580, reduce the levels of soluble CD23 formed by IL-4-stimulated human monocytes or the human monocytic cell line, U937. In contrast to compounds such as the metalloprotease inhibitor batimastat ([4-(N-hydroxyamino)-2-(R)-isobutyl-3-(S)-(2-thiophenethiomethyl)succinyl]-(S)-phenylalanine-N-methylamide, sodium salt), p38 MAPK inhibitors do not directly inhibit proteolytic processing of CD23. Further, evaluation of surface intact CD23 (iCD23) by flow cytometry demonstrated that SK&F 86002 and SB 203580 reduced the surface expression of iCD23 in a concentration-dependent fashion, while batimastat increased the surface expression of iCD23. The decrease in surface iCD23 was accompanied by a decrease in total cell-associated CD23 protein levels but not CD23 mRNA. IL-4 induced a late (>4-h) increase in p38 MAPK activity and corresponding activation of its substrate MAPKAPK-2. This activation was blocked by addition of SB 203580 before IL-4 induction, in parallel with the inhibition of CD23 expression. Modulation of CD23 by antibodies has been shown to alleviate the symptoms of murine collagen-induced arthritis, implicating CD23 as an important proinflammatory agent. These data show that in addition to the known cytokine inhibitory actions of SK&F 86002 and SB 203580, they also confer an additional potential anti-inflammatory activity through modulation of CD23 expression.

Topical sodium cromoglycate in the treatment of moderate-to-severe atopic dermatitis

BACKGROUND

Unsatisfactory treatment results for severe atopic dermatitis have led to many experimental therapies, including cromolyn sodium in various vehicles at concentrations ranging from 1% to 10%. Results suggest that the vehicle used to deliver the cromolyn is relevant to its effectiveness.

OBJECTIVE

To test the efficacy of low concentrations of cromolyn in a water-soluble vehicle in the treatment of moderate-to-severe atopic dermatitis in a double-blind, placebo-controlled study.

METHODS

Twenty-six pediatric patients who had failed to respond to conventional therapy were randomized into 2 treatment groups: patients in group A used the study drug for 1 month (phase I), then received the placebo for 1 month (phase II); and patients in group B used the placebo for 1 month, then received the study drug for 1 month. The study drug was cromolyn sodium inhalation solution mixed into a water-based emollient cream to a final concentration of 0.21%. Upon enrollment and at each follow-up visit, every patient was given a severity score based on extent and severity of skin involvement.

RESULTS

At enrollment, there were no significant differences between groups A and B in severity scores, age, sex, race, skin test and/or RAST positivity, eosinophil levels, IgE concentrations, or the presence of concomitant rhinitis or asthma. After the first phase of the study treatment, severity scores had decreased significantly for both groups with a significant difference between group A (cromolyn) and group B (placebo). After crossover, both groups had significantly lower severity scores than at entry into the study.

CONCLUSION

Treatment with topical cromolyn in a hydrophilic emollient vehicle has a significant anti-inflammatory effect on moderate-to-severe atopic dermatitis. We have now incorporated this treatment into our clinical practice.

The effects of androstenediol and dehydroepiandrosterone on the course and cytokine profile of tuberculosis in BALB/c mice

Immunity to Mycobacterium tuberculosis requires a T helper 1 (Th1) cytokine balance accompanied by tumour necrosis factor-alpha (TNF-alpha), and activated macrophages. These facets of the immune response are sensitive to suppression by glucocorticoids (GC), which can reactivate and exacerbate tuberculosis in man and animals. Dehydroepiandrosterone (DHEA) and its derivative, 3beta,17beta androstenediol (AED), are reported to have antiglucocorticoid properties in vivo. We therefore investigated the effects of predetermined optimal doses of these compounds, on the course of pulmonary tuberculosis in an established model in BALB/c mice in which an early phase of Th1-mediated response accompanied by adrenal hyperplasia, is followed by a switch to Th2, progressive loss of TNF-alpha expression and disease progression. Both compounds were protective, particularly AED which caused a fall in bacterial counts and prolonged survival. These effects correlated with the appearance within 3 days of cellular infiltrates rich in cells expressing interleukin-2 (IL-2), IL-1alpha and TNF-alpha, and with partial suppression of the switch to IL-4 producing cells that occurred in controls. AED also caused enhanced development of granulomas at 14 days, and persistence of granuloma formation to 120 days, with a corresponding suppression of areas affected by pneumonia. Much of the therapeutic effect of AED and DHEA was obtained by treating for only the first 3 weeks, which is the phase of adrenal hyperplasia. These results suggest that the ratio of GC to anti-GC steroids may play a role in the pathogenesis of tuberculosis, and further investigation could lead to novel treatment strategies.

Sympathectomy-induced immune changes are not abrogated by the glucocorticoid receptor blocker RU-486

Removal of sympathetic noradrenergic input to the immune system by injection of 6-hydroxydopamine (6-OHDA) triggers increases in antigen-specific in vitro splenocyte proliferation and cytokine production in BALB/cJ and C57B1/6J mice. This examines the possible role of glucocorticoids in these previously reported changes. In both strains, chemical sympathectomy triggers an elevation of glucocorticoid levels immediately following injection of 6-OHDA, returning to normal within one to two days. In the BALB/cJ strain, glucocorticoid elevation is seen only after the initial 6-OHDA injection; levels in chronically denervated animals are not different from controls. In the C57B1/6J strain, the increase is seen even with chronically denervated animals. Prior implantation of mice with pellets containing the glucocorticoid receptor antagonist RU-486 does not abrogate denervation-induced increases in cytokine production or proliferation in either strain. In addition to the previously reported increased interleukin (IL)-2 and IL-4 production, there is an increase in IFN-gamma production in the C57B1/6J strain following either acute or chronic denervation. The persistence of denervation-induced changes even when the effect of corticosterone is blocked with RU-486 or diminished with chronic denervation indicates that the changes are driven mainly by a glucocorticoid-independent mechanism.

Induction of cytokine receptors by glucocorticoids: functional and pathological significance

Current concepts on the role of glucocorticoid hormones in the regulation of inflammatory and immune responses depict this role as being inhibitory. Over the past decade, however, a large variety of studies have shown that glucocorticoids also exert stimulatory effects on immune function, suggesting that the present concept of the role of glucocorticoids in the immune system in not sufficient and needs to be extended. Here, Jan Wiegers and Hans Reul ask how these apparently paradoxical effects fit together and what their functional and pathological significance might be.

Differential Regulation of Interleukin-10 (IL-10) and IL-12 by Glucocorticoids In Vitro

Antigen-presenting cells are thought to modulate the development of Th1 and Th2 cells by the secretion of interleukin-10 (IL-10) and IL-12. Because glucocorticoids (GC) favor the development of Th2 responses, we determined whether dexamethasone (DEX) and hydrocortisone (HC) have differential effects on lipopolysaccharide-induced IL-10 and IL-12 production in whole-blood cultures. Significant inhibition of IL-12(p40) and IL-12(p70) was found with 10−8 mol/L and 10−9 mol/L DEX respectively, whereas IL-10 was relatively insensitive or even stimulated. Accordingly, the expression of IL-12(p40) and IL-12(p35) mRNA was more sensitive to DEX than IL-10 mRNA. The glucocorticoid receptor (GR) antagonist RU486 enhanced IL-12 production and largely abrogated the inhibition of IL-12 by GC, indicating that this suppression was mainly GR-mediated. High concentrations of RU486 were inhibitory for IL-10, suggesting that GC may exert a positive effect on IL-10. In the presence of neutralizing anti–IL-10 antibodies, DEX was still capable of IL-12 suppression whereas RU486 still enhanced IL-12 production, indicating that GC do not modulate IL-12 via IL-10 exclusively. Taken together these results indicate that GC may favor Th2 development by differential regulation of IL-10 and IL-12.

Differential Regulation of Interleukin-10 (IL-10) and IL-12 by Glucocorticoids In Vitro

Antigen-presenting cells are thought to modulate the development of Th1 and Th2 cells by the secretion of interleukin-10 (IL-10) and IL-12. Because glucocorticoids (GC) favor the development of Th2 responses, we determined whether dexamethasone (DEX) and hydrocortisone (HC) have differential effects on lipopolysaccharide-induced IL-10 and IL-12 production in whole-blood cultures. Significant inhibition of IL-12(p40) and IL-12(p70) was found with 10−8 mol/L and 10−9 mol/L DEX respectively, whereas IL-10 was relatively insensitive or even stimulated. Accordingly, the expression of IL-12(p40) and IL-12(p35) mRNA was more sensitive to DEX than IL-10 mRNA. The glucocorticoid receptor (GR) antagonist RU486 enhanced IL-12 production and largely abrogated the inhibition of IL-12 by GC, indicating that this suppression was mainly GR-mediated. High concentrations of RU486 were inhibitory for IL-10, suggesting that GC may exert a positive effect on IL-10. In the presence of neutralizing anti–IL-10 antibodies, DEX was still capable of IL-12 suppression whereas RU486 still enhanced IL-12 production, indicating that GC do not modulate IL-12 via IL-10 exclusively. Taken together these results indicate that GC may favor Th2 development by differential regulation of IL-10 and IL-12.

Cytokines as targets for the inhibition of eosinophilic inflammation

Eosinophilic inflammation is thought to play a central role in the pathogenesis of asthma. The immunoregulatory effects of interleukin (IL)-4, IL-5 and immunoglobulin (Ig)E suggest that these molecules play key roles in the effector function of eosinophils and mast cells. IL-4 regulates the development of CD4+ TH2-type cells, which elicit essential signals through IL-4 and IL-5 for the regulation of IgE production and eosinophilia, respectively. IL-5-regulated pulmonary eosinophilia and airways dysfunction can also occur independently of IL-4 and allergen-specific Igs. Such IL-4-independent pathways may also play a substantive role in the aetiology of asthma. Thus, evidence is now emerging that allergic airways disease is regulated by humoral and cell-mediated components. The essential and specific role of IL-5 in regulating eosinophilia, and the subsequent involvement of this leukocyte in the induction of lung damage and airways dysfunction, identifies IL-5 as a primary therapeutic target for the relief of airways dysfunction in asthma.

An intranasal glucocorticoid inhibits the increase of specific IgE initiated during birch pollen season

BACKGROUND

Recent in vitro findings show that glucocorticoids in combination with IL-4 can induce the synthesis of IgE, indicating that glucocorticoids may promote allergy.

OBJECTIVE

A double-blind, placebo-controlled study was performed to evaluate the effect of an intranasal glucocorticoid on the levels of birch pollen-specific IgE antibodies in serum from patients with allergic rhinitis.

METHODS

Eighteen patients with allergic rhinitis received treatment with an intranasal glucocorticoid (beclomethasone dipropionate, 400 microg/day) or placebo for 5 weeks, starting from the beginning of the birch pollen season. Blood samples for anti-birch IgE evaluation were taken before treatment was initiated and at 2 and 5 weeks after the beginning of the study.

RESULTS

The beclomethasone group (n = 9) had significantly lower symptom scores when compared with the placebo group (n = 9) (0.86 +/- 0.26 vs 2.79 +/- 0.76, p value = 0.01). Both the treatment group and the placebo group showed a trend of an increase in anti-birch IgE levels 2 weeks after the beginning of the treatment (from 33.1 +/- 13.1 kU/L to 44.9 +/- 20.9 kU/L in the beclomethasone group and from 53.2 +/- 18.9 kU/L to 64.1 +/- 22.1 kU/L in the placebo group). Treatment with beclomethasone returned anti-birch IgE levels to baseline by the end of the study, whereas in the placebo group the anti-birch IgE levels continued to increase (final values, 33.1 +/- 11.9 kU/L vs 72.6 +/- 23.2 kU/L, respectively). The change in IgE antibody levels in the placebo group was significantly higher than that in the beclomethasone group. No statistically significant changes in total IgE or soluble CD23 levels were detected.

CONCLUSION

We conclude that treatment with an intranasal glucocorticoid initiated at the beginning of the pollen season inhibits the induced increase in specific IgE.

Glucocorticoids and the immune function in the human immunodeficiency virus infection: a study in hypercortisolemic and cortisol-resistant patients

Immunological studies in human immunodeficiency virus (HIV)-positive patients suggest that the disease progression is accompanied by a defective production of type 1 cytokines (interleukin-2 (IL-2) and IL-12], an increased production of type 2 cytokines (IL-4, IL-6, and IL-10), and an increased production of IgE. HIV infection is also associated with activation of the hypothalamo-pituitary-adrenal axis function and increased plasma and urinary cortisol concentrations. As cortisol is involved in the physiological regulation of cytokines, a study was conducted to examine cytokine patterns in two groups of hypercortisolemic patients, one with normal sensitivity to glucocorticoids and the other with glucocorticoid resistance. Ten HIV-infected patients with normal receptor affinity to glucocorticoids (AIDS-C), 10 HIV-infected patients with low receptor affinity to glucocorticoids (AIDS-GR), and 20 healthy subjects were studied. Receptor characteristics of peripheral blood mononuclear cells were evaluated by [3H]dexamethasone binding. Serum cortisol and urinary free cortisol were measured by RIA. Serum ACTH and IgE were measured by immunoradiometric assay, and IL-2, IL-4, and IL-10 cytokines and interferon-gamma were measured by enzyme-linked immunosorbent assay. AIDS-C patients showed low IL-2 and high IL-4, IL-10, and IgE concentratios; conversely, AIDS-GR patients showed high IL-2 and low IL-4 and IgE concentrations. Thus, in HIV infection, elevated cortisol levels suppress cell-mediated immunity and stimulate humoral immunity, whereas this response is not detected in cortisol-resistant patients. These findings indicate that cortisol and its receptors are critically involved in the regulation of immune function in HIV infection.

Glucocorticoids inhibit human antigen-specific and enhance total IgE and IgG4 production due to differential effects on T and B cells in vitro

Although anti-inflammatory properties of glucocorticoids (GC) are well documented, their activity in allergic diseases is still controversial. Recently, it has been reported that GC can increase, both in vivo and in vitro, the polyclonal production of total IgE. In this study we investigated the effects of GC on the antigen (Ag)-specific IgE response in a human in vitro system with peripheral blood mononuclear cells or B cells of bee venom-sensitized individuals that allows the production of bee venom phospholipase A2 (PLA)-specific IgE and IgG4 antibodies (Ab). PLA-specific Ab were induced by simultaneously activating T cells and B cells specifically with allergen and polyclonally with anti-CD2 and soluble CD40 ligand (sCD40L) in the presence of interleukin (IL)-4. Indeed, dexamethasone and prednisolone enhanced the formation of total IgE and IgG4 in PBMC, while the production of PLA-specific IgE and IgG4 Ab was selectively inhibited in a dose-dependent manner. The suppressive effect of GC was mediated during Ag-specific stimulation and T cell-B cell interaction. This was due to GC suppressing specific T cell proliferation and cytokine production, whereas neither allergen-specific nor total IgE and IgG4 production by sCD40L/IL-4-stimulated pure B cells was affected. In contrast to GC, cyclosporine A inhibited both total and PLA-specific IgE and IgG4 secretion in peripheral blood mononuclear cells and B cell cultures. Further experiments showed that increase in nonspecific total isotype response resulted from inhibition of IL-4 uptake by cells other than B cells and sufficient availability of IL-4 to B cells for isotype switch and synthesis. Furthermore, demonstration of opposite regulatory effects of GC on specific and total isotype formation in vitro, including the inhibition of allergy-relevant Ag-specific IgE response, may contribute to a better understanding of apparently controversial observations, and explain why most allergic patients benefit from GC therapy.

Clinical applications of cytokines: new directions in the therapy of atopic diseases

OBJECTIVES

This review will enable the readers to understand the pathogenesis of allergic inflammation, and the role of various cells and cytokines in allergic diseases. Pathogenic cytokines may become key therapeutic targets in the future treatment of allergic diseases.

DATA SOURCES

MEDLINE literature search limited to the English language was performed using the relation between specific cytokines and allergic inflammation as well as therapy of allergic diseases. Relevant articles referenced in retrieved sources and current texts on ctyokines and allergic responses were also utilized.

RESULTS

The mechanism underlying allergic inflammation involves complex interactions between various cells and cytokines. The immediate reaction is caused mainly by mast cells and followed by a cell mediated response that involves eosinophils, mononuclear cells, neutrophils, T lymphocytes and macrophages. The majority of T cells in early allergic reactions are T helper type 2 (TH2)-like producing IL-4, IL-5, IL-13 but not IFN-gamma. These cytokines regulate IgE synthesis, promote eosinophil differentiation and survival, and induce vascular endothelial adhesion molecules, thus contributing to allergic inflammation.

CONCLUSIONS

Although studies of cytokine modulation have utilized animal models of allergic diseases, the increasing availability of recombinant cytokines and cytokine antagonists is likely to lead to more wide scale applications in allergic diseases.

Gulf War syndrome: is it due to a systemic shift in cytokine balance towards a Th2 profile?

The symptoms of Gulf War syndrome are compatible with the hypothesis that the immune system of affected individuals is biased towards a Th2-cytokine pattern. Factors that could lead to a Th2 shift among Gulf War veterans include exposure to multiple Th2-inducing vaccinations under stressful circumstances and the way in which such vaccinations were administered, which would be expected to maximise Th2 immunogenicity. These factors may have led to a long-term systemic shift towards a Th2-cytokine balance and to mood changes related to the immunoendocrine state. Other vaccines that lead to similar long-term, non-specific shifts in cytokine balance are well-established. If our hypothesis is proven, treatment may be possible with regimens that induce a systemic Th1 bias.

Development of immune functions related to allergic mechanisms in young children

The newborn immune system differs quantitatively and functionally from that of adults. Development of the immune system has important implications for childhood diseases. The immaturity of the immune system in the first years of life may contribute to failure of tolerance induction and in the development of allergic disease. T cell function is diminished, especially the capacity to produce cytokines; production of interferon (IFN)-gamma, and IL-4 is strongly reduced. IFN-gamma has been found to be even lower in cord blood of newborns with a family history of atopy. Differences in other cell types (natural killer cells, antigen-presenting cells, and B cells) could also play a role in the development of allergic disease. Current data suggest that irregularities in IgE synthesis, helper T cell subsets (Th1, Th2, CD45RA, and CD45RO), cytokines (IL-4, IFN-gamma), and possibly other cell types may play a role in the development of allergy in childhood. Moreover, the role of cell surface molecules, like co-stimulatory molecules (CD28, CD40L), activation markers (CD25), and adhesion molecules (LFA-1/ICAM-1, VLA-4/ VCAM-1) is also discussed. These variables are modulated by genetic (relevant loci are identified on chromosome 5q, 11q, and 14) and environmental forces (allergen exposure, viral infections, and smoke). The low sensitivity of current predictive factors for the development of allergic diseases, such as cord blood IgE levels, improves in combination with family history and by measurement of in vitro responses of lymphocytes and skin reactivity to allergens. New therapeutic approaches are being considered on the basis of our current understanding of the immunopathology of allergic disease, for instance cytokine therapy and vaccination with tolerizing doses of allergen or peptides.

Mechanisms of inhibition of IgE synthesis by nedocromil sodium: nedocromil sodium inhibits deletional switch recombination in human B cells

IgE synthesis requires IL-4 and a T cell-B cell interaction that involves the B-cell antigen CD40 and its ligand expressed on activated T cells. Nedocromil sodium (NS), an effective prophylactic agent in asthma, inhibits IgE synthesis by human B cells. In this report we examined the mechanisms of this inhibition. NS targeted the B cells because it inhibited IgE synthesis induced by anti-CD40 and IL-4 in highly purified B cells (greater than 98% CD19+). NS had no effect on the induction of epsilon-germline transcripts by IL-4 but strongly inhibited CD40-mediated S mu --> S epsilon deletional switch recombination. The effect of NS was not specific for CD40 because it inhibited IgE synthesis in B cells stimulated with hydrocortisone plus IL-4. Moreover, the effect of NS was not specific for IgE because it inhibited CD40/IL-4-driven IgG4 synthesis by B cells sorted for lack of surface expression of IgG4. NS caused only modest inhibition of spontaneous IgE synthesis by B cells from patients with hyper-IgE syndrome, suggesting that it has little effect on B cells that have already undergone isotype switching. These results strongly suggest that NS inhibits IgE isotype switching by inhibiting deletional switch recombination and that NS has a novel potential mechanism for the prevention of asthma and other allergic diseases.

RANTES and macrophage inflammatory protein 1 alpha selectively enhance immunoglobulin (IgE) and IgG4 production by human B cells

We studied the effects of various chemokines including neutrophil-activating peptide 2 (NAP-2), beta-thromboglobulin (beta-TG), platelet factor 4 (PF-4), melanoma growth stimulating activity (GRO), gamma interferon-induced protein (IP-10), regulated on activation, normal T expressed and secreted (RANTES), macrophage inflammatory protein 1 alpha (MIP-1 alpha), MIP-1 beta, and monocyte chemotactic protein 1 (MCP-1) on Immunoglobulin (IgE) and IgG4 production by human B cells. None of these chemokines with or without interleukin (IL-4), anti-CD40 or -CD58 monoclonal antibody (mAb), induced IgE and IgG4 production by B cells from nonatopic donors. However, RANTES and MIP-1 alpha selectively enhanced IgE and IgG4 production induced by IL-4 plus anti-CD40 or -CD58 mAb without affecting production of IgM, IgG1, IgG2, IgG3, IgA1, or IgA2, whereas other chemokines failed to do so. Enhancement of IgE and IgG4 production by RANTES and MIP-1 alpha was specifically blocked by anti-RANTES mAb and anti-MIP-1 alpha antibody (Ab), respectively, whereas anti-IL-5 mAb, anti-IL-6 mAb, anti-IL-10 Ab, anti-IL-13 Ab, and anti-tumor necrosis factor-alpha mAb failed to do so. Purified surface IgE positive (slgE4) and slgG4+ B cells generated either in vitro or in vivo spontaneously produced IgE and IgG4, respectively, whereas sIgE- and sIgG4- B cells failed to do so. RANTES and MIP-1 alpha enhanced spontaneous IgE and IgG4 production in slgE+ and slgG4- B cells, respectively, whereas neither RANTES nor MIP-1 alpha did so in sIgE- or sIgG4- B cells. Purified sIgE4+ and sIgG4+, but not sIgE- or sIgG4- B cells, generated in vitro and in vivo expressed receptors for RANTES and MIP-1 alpha, whereas they failed to express receptors for other chemokines. These findings indicate that RANTES and MIP-1 alpha enhance IgE and IgG4 production by directly stimulating sIgE+ and sIgG4+ B cells.

Hydrocortisone enhances total IgE levels--but not the synthesis of allergen-specific IgE--in a monocyte-dependent manner

Recently, hydrocortisone (HC), when combined with human IL-4, has been reported to increase IgE levels in supernatants (SN) of in vitro cultured leucocytes. In this study we investigated the influence of HC on allergen-specific IgE synthesis. Moreover, we examined the relevance of different cell types in this respect. Peripheral blood mononuclear cells (PBMC), T-cell depleted PBMC, CD14-depleted PBMC and highly purified B cells from 10 allergic (birch pollen and/or grass pollen) patients and five non-allergic individuals were investigated. The cells were incubated with HC and/or recombinant human IL-4 (rIL-4) for 8 days. A considerable increase of total IgE was observed in HC/rIL-4-stimulated cultures compared with rIL-4 alone, HC alone or non-stimulated cultures. We demonstrate that this effect depends on the presence of monocytes in in vitro cultures. These results were seen in every experiment, irrespective of healthy or atopic state of the blood donor. The increase of IgE could not be attributed to a rise of birch pollen-and/or grass pollen-specific IgE in patients allergic to these allergens, as shown by IgE-immunoblot. Radio-allergosorbent test (RAST) investigations of HC/rIL-4-stimulated cells cultures from allergic and non-allergic patients confirmed that HC/rIL-4-induced elevated IgE production was also not due to increased production of IgE, specific for important aero-allergens (pollens, house dust mite or animal dander). Therefore we conclude that newly synthesized IgE is not specific for allergens, but that sequential isotype switching in human B cells leads to increased polyclonal IgE production.

Inhibition of IL-4 receptor up-regulation on B cells by antisense oligodeoxynucleotide suppresses IL-4-induced human IgE production

IL-4 is shown to up-regulate its own receptor (IL-4R) on human lymphocytes, but the functional significance of up-regulated IL-4R is not clear regarding IgE production. This study investigated the possible role of IL-4-induced up-regulation of IL-4R on B cells in the induction of human IgE synthesis by means of antisense strategy. Among three antisense oligodeoxynucleotides designed against the downstream of translation initiation site of IL-4R cDNA, S-oligo 1, complementary to nucleotide 1-24, showed the strongest inhibition of the constitutive expression of IL-4R on Daudi cells. Addition of S-oligo 1 together with IL-4 also decreased the up-regulated but not constitutive levels of IL-4R on peripheral blood B cells without affecting the concomitant enhancement of CD23, CD40, HLA-DR and surface IgM expression, indicating that its effect is specific for IL-4R up-regulation. When S-oligo 1 was added to B cells costimulated with IL-4 and anti-CD40 MoAb, it induced a dose-dependent inhibition of IgE production. This inhibition was accompanied by a decrease in the expression of mature C epsilon transcripts, whereas the accumulation of germ-line C epsilon transcripts was not affected by S-oligo 1. These data suggest that the signal transduction mediated by the up-regulated IL-4R on B cells may be intimately associated with the induction of isotype switching to IgE that leads to mature C epsilon transcription and IgE production.

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.

Differential effects of gangliosides on human IgE and IgG4 production

The effects of gangliosides on human IgE and IgG4 production were studied. Of the various gangliosides tested, only GM2 and GM3 inhibited the IgE and IgG4 production induced by interleukin (IL)-4 plus hydrocortisone (HC), or that induced by IL-13 plus HC, in human surface IgE- and IgG4-negative (sIgE-, sIgG4-) B cells without affecting the production of IgG1, IgG2, IgG3, IgM, IgA1 or IgA2. In contrast, GM1, GD1a, GD1b, GD3, GT1b and GQ1b were without effects. The GM2- and GM3-mediated inhibition was specific, since each was blocked by a corresponding antibody. Of the various factors tested. IL-6, IL-10, and tumor necrosis factor (TNF)-alpha enhanced the IgE and IgG4 production induced by IL-4 plus HC or by IL-13 plus HC, while IL-8 and transforming growth factor (TGF)-beta inhibited these responses. However, only TNF-alpha counteracted the GM2- and GM3-mediated inhibition of IgE and IgG4 production, while IL-6, IL-10, anti-IL-8 monoclonal antibody and anti-TGF-beta antibody failed to do so. Anti-TNF-alpha monoclonal antibody, but not control IgG1, not only inhibited IgE and IgG4 production in the absence of TNF-alpha but also blocked the counteraction of inhibition by TNF-alpha. In cultures containing IL-4 plus HC or IL-13 plus HC. GM2 and GM3 specifically inhibited TNF-alpha production without affecting TNF-alpha receptors, IL-6 production or IL-6 receptors. These results indicate that GM2 and GM3 inhibit IgE and IgG4 production by inhibiting endogenous TNF-alpha production.

The role of eosinophils in the pathogenesis of asthma

The eosinophil is regarded as a key mediator of the pathology and abnormal physiology of bronchial asthma. Current investigations are directed at understanding how eosinophils are attracted into the respiratory tract and how they bring about the abnormalities characteristic of this disease.

T cell clones from an X-linked hyper-immunoglobulin (IgM) patient induce IgE synthesis in vitro despite expression of nonfunctional CD40 ligand

The induction of immunoglobulin E (IgE) switching in B cells requires at least two signals. The first is given by either of the soluble lymphokines interleukin 4 (IL-4) or IL-13, whereas the second is contact dependent. It has been widely reported that a second signal can be provided by the CD40 ligand (CD40L) expressed on the surface of T cells, mast cells, and basophils. A defect in the CD40L has been shown recently to be responsible for the lack of IgE, IgA, and IgG, characteristic of the childhood X-linked immunodeficiency, hyper IgM syndrome (HIGM1). IgE can however be detected in the serum of some HIGM1 patients. In this study, we isolated T cell clones and lines using phytohemagglutinin (PHA) and allergen, respectively, from the peripheral blood of one such patient who expressed a truncated form of CD40L, and investigated their ability to induce IgE switching in highly purified, normal tonsillar B cells in vitro. Unexpectedly, 4 of 12 PHA clones tested induced contact-dependent IgE synthesis in the presence of exogenous IL-4. These clones were also shown to strongly upregulated IL-4-induced germline epsilon RNA and formed dense aggregates with B cells. Of the four helper clones, three were CD8+, of which two were characteristic of the T helper cell 2 (Th2) subtype. Two allergen-specific HIGM1 T cell lines, both of the Th0 subtype, could also drive IgE synthesis when prestimulated using specific allergen. All clones and lines were negative for surface expression of CD40L, and the mutated form of CD40L was confirmed for a representative clone by RNase protection assay and sequencing. The IgE helper activity could not be attributed to membrane tumor necrosis factor alpha (TNF-alpha) although it was strongly expressed on activated clones, and the addition of neutralizing anti-TNF-alpha antibody did not abrogate IgE synthesis. These results therefore suggest the involvement of T cell surface molecules other than CD40L in the induction of IgE synthesis, and that these molecules may also be implicated in other aspects of T-B cell interactions.

In vitro and in vivo effect of glucocorticoids on IgE and IgG subclass secretion

Hydrocortisone (HC) as well as its synthetic derivatives have been shown to strongly enhance interleukin-4 (IL-4)-induced in vitro IgE synthesis. To investigate possible effects on IgG subclasses, peripheral blood mononuclear cells (PBMC) were incubated with different glucocorticosteroids in the absence or presence of IL-4. The glucocorticoids alone led to a strongly enhanced secretion of IgG1, IgG2 and IgG3, but not IgG4. The addition of IL-4 induced marked increases in IgG1 and IgG4, no changes in IgG3, but a consistent decrease in IgG2 synthesis. In order to find out whether these profound in vitro effects of corticosteroids are also reflected by changes in antibody serum levels during steroid treatment, 10 healthy volunteers took 25 mg prednisone for 7 consecutive days. We could not observe any significant changes of IgE or IgG subclass serum levels during or after this period. However, cell cultures performed after the glucocorticoid treatment revealed a marked decrease in the ability to produce IgG4 and a significantly lower potential to produce IgE in response to IL-4 alone or IL-4 and HC. We conclude that, although strongly implicated by the in vitro results, glucocorticosteroid treatment does not result in an increased allergy risk.

Glucocorticoids and the immune system in AIDS

Data reported in the literature show in the majority of cases an increased basal cortisol level in HIV-positive patients compared with controls, although the plasma concentration of cortisol in HIV-positive patients is generally within the physiological range. It is well known that pharmacological doses of glucocorticoids are immunosuppressive, but little is known about the effects of physiological concentrations of cortisol on the immune system. If a dialogue really exists between the HPA axis and the immune system, immune responses should be modulated by physiological concentrations of cortisol, as well as pathological levels of cortisol (high as in Cushing's syndrome or low as in Addison's disease), which are known to be associated with impaired immune system responses. We suggest that in HIV-positive patients, a chronic increase in the basal endogenous cortisol levels may provoke an imbalance in cytokine production, with a decrease in the production of type 1 and an increase in that of type 2. The type 1 to type 2 shift might be synergic with the increased cortisol levels in enhancing viral replication and apoptotic phenomena, and finally in causing the progression of HIV infection.

TH2 and 'TH2-like' cells in allergy and asthma: pharmacological perspectives

Recently, considerable progress has been made in understanding the molecular basis by which cytokines released from CD4+ helper T cells contribute to allergic disease. A subset of CD4+ helper T cells, termed TH2 cells, produce interleukin 4 (IL-4) and IL-5, but not interferon gamma. IL-4 has a critical role in causing B-cell immunoglobulin-isotype switch leading to IgE synthesis, and IL-5 governs eosinophilic inflammation of airway tissue. Studies on the mechanisms whereby TH2 cells, and non-T cells such as metachromatic cells, produce a highly restricted panel of cytokines has revealed molecular mechanisms that may affect our views on the induction and treatment of asthma, and these are discussed in this review by Gary Anderson and Anthony Coyle. TH2 cytokine biology may enable pharmacologists to design better, and perhaps even preventative, therapies for the treatment of asthma and allergy. Surprisingly IL-4, rather than IL-5, is emerging as a critical drug target owing to its central role in the regulation of CD4+ helper T cell phenotype commitment.

Hormonal regulation of immune responses

Females have stronger immune responses than males. Female predominance in autoimmune diseases in both experimental animals and in man is also established. Sex hormones and some other steroid hormones have been shown to exert immunoregulatory effects in both in vivo and in vitro situations. Important mechanisms of hormone action on lymphocytes have gradually been revealed. In this paper the most intriguing effects of steroid hormones on immune system and present data suggesting hormonal influence on the pathogenesis of autoimmune diseases are summarized.

Neuropeptides are potent modulators of human in vitro immunoglobulin E synthesis

We determined the effect of adrenocorticotropin hormone (ACTH) on the regulation of IgE synthesis. Depending on the concentration, ACTH enhanced or inhibited IgE synthesis in a culture system where IgE synthesis was induced with interleukin-4 (IL-4) and anti-CD40 monoclonal antibody in peripheral blood mononuclear cells. Similar effects on IgE synthesis were observed by adding ACTH-related peptides, e.g. corticotropin-releasing factor (CRF), the inducer of ACTH, or alpha-melanocyte stimulating hormone (alpha-MSH), a cleavage product of ACTH. However, ACTH had no effect on IgG or IgM synthesis in this culture system. ACTH did not act directly on either B or T cells as there was no influence on IgE synthesis in a system using purified B cells alone or co-cultured with T cells. The effect of ACTH on IgE synthesis was mediated by accessory cells. This was shown by priming purified CD14-positive monocytes with ACTH and reconstitution experiments. Therefore, these findings suggest that ACTH and the related peptides CRF and alpha-MSH can influence the microenvironment modulating an IL-4 and anti-CD40 monoclonal antibody driven class switching to IgE via accessory cells.

Mechanisms of the human allergic response. Clinical implications

During the past decade, there have been enormous strides made in our understanding of the mechanisms underlying the human allergic response. In particular, interleukin-4 and interleukin-5 play a critical role in this process. This article details the understanding of the mechanisms underlying the regulation of allergic response, which is critical to the development of new treatment of allergic diseases.

Synthetic glucocorticoids potentiate IgE synthesis. Influence of steroid and nonsteroid hormones on human in vitro IgE secretion

Recently, hydrocortisone (HC) has been shown significantly to enhance interleukin-4 (IL-4)-induced in vitro IgE synthesis. For investigation of possible effects of synthetic corticosteroids but also of effects of other important human hormones, peripheral blood mononuclear cells (PBMC) were incubated with IL-4 and various concentrations of the hormones. IgE secreted in the supernatant was determined after a 14-d culture period. Like HC, all synthetic corticosteroids potentiated IgE secretion. A minor effect was noted for the mineralocorticoid aldosterone. No modulating effect on IL-4-induced IgE formation was observed for adrenocorticotropic hormone (ACTH), somatotropin (STH), thyroid-stimulating hormone (TSH), triiodothyronine, thyroxine, epinephrine, noradrenaline, insulin, and glucagon.