Glucocorticoids suppressed production and gene expression of interleukin-5 by peripheral blood mononuclear cells in atopic patients and normal subjects

An evaluation of mepolizumab for the treatment of severe asthma

Introduction: Asthma is considered one of the most common chronic conditions globally, characterized by variable airflow obstruction and symptoms. Severe asthma is diagnosed when asthma control requires high-intensity therapy or continues to remain uncontrolled despite treatment. Eosinophilic inflammation is known to be perpetuated by the activity of IL-5 in a proportion of severe asthma subjects, and targeting IL-5 may offer a therapeutic option. Areas covered: In this review, we discuss the role and pathogenesis of IL-5 and eosinophils in asthma and rationale of antagonizing IL-5 in severe eosinophilic asthma. Mepolizumab is the first of three anti-IL-5 biologics licensed in 2015 for use in this subgroup of patients. We discuss clinical and real-life studies leading up to its approval and post-marketing outcomes in terms of efficacy and safety to-date, as well as its pros and cons. Expert opinion: IL-5 antagonism has paved the way for an additional personalized therapeutic opportunity for use in severe asthma with eosinophilic inflammation, though there is limited evidence on the long-term implications of suppressing/depleting eosinophils and the duration for which they should be administered.

Multiplicity of Glucocorticoid Action in Inhibiting Allograft Rejection

Glucocorticoids (GCs) are used as immunosuppressive and antiinflammatory agents in organ transplantation and in treating autoimmune diseases and inflammatory disorders. GCs were shown to exert their antiproliferative effects directly through blockade of certain elements of an early membrane-associated signal transduction pathway, modulation of the expression of select adhesion molecules, and by suppression of cytokine synthesis and action. GCs may act indirectly by inducing lipocortin synthesis, which in turn, inhibits arachidonic acid release from membrane-bound stores, and also by inducing transforming growth factor (TGF)-β expression that subsequently blocks cytokine synthesis and T cell activation. Furthermore, by preferentially inhibiting the production of Th1 cytokines, GCs may enhance Th2 cell activity and, hence, precipitate a long-lasting state of tolerance through a preferential promotion of a Th2 cytokine-secreting profile. In exerting their antiproliferative effects, GCs influence both transcriptional and posttranscriptional events by binding their cytosolic receptor (GR), which subsequently binds the promoter region of cytokine genes on select DNA sites compatible with the GCs responsible elements (GRE) motif. In addition to direct DNA binding, GCs may also directly bind to, and hence antagonize, nuclear factors required for efficient gene expression, thereby markedly reducing transcriptional rate. The pleiotrophy of the GCs action, coupled with the diverse experimental conditions employed in assessing the GCs effects, indicate that GCs may utilize more than one mechanism in inhibiting T cell activation, and warrant careful scrutiny in assigning a mechanism by which GCs exert their antiproliferative effects. © 1998 Elsevier Science Inc.

Polyclonal and allergen-induced cytokine responses in adults with asthma: resolution of asthma is associated with normalization of IFN-gamma responses

BACKGROUND

Atopic disease is associated with skewing of immune responses away from a T(H)1 toward a T(H)2 profile. Previous studies have implicated this cytokine imbalance in the development of disease. However, it is not known whether normalization of this imbalance is conversely associated with disease resolution.

OBJECTIVE

To further delineate the role of reduced T(H)1 and increased T(H)2 cytokine production in the pathogenesis of atopic disease and to determine whether disease resolution is associated with alteration of cytokine profiles, we investigated cytokine responses in a cohort of adult patients with asthma followed from childhood.

METHODS

A cohort of wheezy children and control subjects aged 7 to 10 years were recruited from 1964 to 1967. Subjects were reevaluated every 7 years to monitor the outcome of childhood asthma. At the 42-year follow-up, 89 subjects from this cohort were evaluated for mitogen and house dust mite (HDM)-induced T(H)1 (IFN-gamma) and T(H)2 (IL-4, IL-5, and IL-13) cytokine responses. Cytokine responses were compared in patients with ongoing asthma, patients with resolved asthma, and control subjects.

RESULTS

Patients with severe ongoing asthma had significantly reduced HDM-induced IFN-gamma production compared with that of control subjects and patients with resolved asthma. In contrast, HDM-induced IFN-gamma production in patients with resolved asthma was equivalent to that seen in control subjects. Patients with ongoing and resolved asthma produced significantly higher levels of IL-5 in response to HDM compared with that seen in control subjects, with levels being equivalent in patients with active and resolved asthma. HDM-induced IL-13 production was significantly increased in the patients with resolved asthma when compared with that seen in the control subjects. PHA-induced cytokine responses did not parallel HDM-induced responses.

CONCLUSION

Patients with persistent and severe atopic asthma have a reduced HDM-induced T(H)1 response, whereas those with resolved asthma do not. This suggests that reduced HDM-induced IFN-gamma production might be an important factor contributing to ongoing severe asthma and that normalization of allergen-induced T(H)1 responses might be important for disease resolution. The finding that all subjects with a history of asthma displayed increased HDM-induced T(H)2 (IL-5 and IL-13) cytokine responses, irrespective of the presence or absence of asthma, suggests that increased T(H)2 responses reflect the presence of the atopic state per se rather than being specifically linked to asthma.

Transcriptional and post-transcriptional mechanisms of glucocorticoid antiproliferative effects

Glucocorticoids (GCs) are used as immunosuppressive and anti-inflammatory agents in treating organ transplantation rejection, autoimmune diseases, (hematological) cancers, and inflammatory disorders. GCs exert their effects through a multitude of mechanisms, the most significant of which is inhibition of cytokine production, and for some cytokines their effects on target cells. Paradoxically, GCs also upregulate the expression of (pro-inflammatory) high-affinity cytokine receptors on target cells in the face of lost ligand (cytokine) stimulation. GC inhibition of cytokine expression occurs at both transcriptional and post-transcriptional levels. GCs acted transcriptionally by binding their cytosolic receptor (GR), thereby facilitating its nuclear translocation and subsequent binding to the promoter region of cytokine genes on sites compatible with GC response element (GRE) motifs, which in turn directly or indirectly regulated gene expression. In addition to direct DNA binding, GCs acted post-transcriptionally by: (1) antagonism of nuclear factors required for efficient gene expression either directly or through induction of the expression of specific transcription factor antagonists, (2) altered Th lineage development by favouring the generation of (anti-inflammatory) Th2 cells and suppressing the induction or the activity of established (pro-inflammatory) Th1 cells, and (3) stimulating the expression of transforming growth factor (TGF)-beta, an immunosuppressive cytokine which inhibited cytokine production. However, these mechanisms are not mutually exclusive, since GCs may utilize more than one mechanism in exerting their anti-proliferative effect.

Differential effect of phosphodiesterase inhibitors on IL-13 release from peripheral blood mononuclear cells

Increased cyclic AMP (cAMP)-phosphodiesterase (PDE) activity in peripheral blood leucocytes is associated with the immunological inflammation that characterizes allergic diseases, such as atopic dermatitis and allergic rhinitis. Recently, it has been found that IL-13 has similar biological functions to IL-4. The aim of this study was to investigate the possible involvement of cAMP-PDE activity on IL-13 release from peripheral blood mononuclears cells (PBMC) from atopic asthma patients. Phytohaemagglutinin (PHA)-induced IL-13 release from PBMC was concentration-dependently inhibited by rolipram, a type 4 PDE inhibitor, as well as by dibutyryl cAMP, a membrane-permeant cAMP analogue. However, theophylline, a non-specific PDE inhibitor, and cilostazol, a type 3 PDE inhibitor, failed to inhibit IL-13 release. The inhibitory effect of rolipram was enhanced by the addition of forskolin (10(-4) m), an adenylyl cyclase stimulator. PHA itself did not alter the intracellular cAMP level. Rolipram concentration-dependently increased cAMP level in PHA-stimulated PBMC, and this increase was synergistically facilitated by the addition of forskolin (10(-4) m). These results suggest that type 4 PDE inhibitors, alone or synergistically in combination with forskolin, inhibit PHA-induced IL-13 release from PBMC of atopic asthma patients by elevating intracellular cAMP concentrations. These inhibitors have the potential to exert an anti-inflammatory effect by inhibiting IL-13 production in allergic diseases such as atopic asthma.

Y-24180, an antagonist of platelet-activating factor, suppresses interleukin 5 production in cultured murine th(2)cells and human peripheral blood mononuclear cells

Interleukin (IL)-5 has been shown to play an essential role in the pathogenesis of airway inflammation. We investigated the effect of 4-(2-chlorophenyl)-2-[2-(4-isobutylphenyl)ethyl]-6, 9-dimethyl-6 H -thieno[3,2- f ][1,2,4]triazolo[4,3- a][1,4]diazepine (Y-24180), an antagonist of platelet-activating factor (PAF), on the production of IL-5 in cultured D10.G4.1 cells, a murine Th(2)clone, and human peripheral blood mononuclear cells (PBMC). As a result, Y-24180 was found to suppress both the mRNA expression of IL-5 and the subsequent secretion of this cytokine in antigen-stimulated D10.G4.1 cells. Y-24180 also suppressed the production of IL-4, another Th(2)type cytokine, at the level of mRNA expression, however, it hardly affected the mRNA expression for IL-6 or IL-10, thus indicating it to have a selective action against IL-5 and IL-4. The suppressive effect of Y-24180 on the secretion of IL-5 by human PBMC was more potent than that of WEB2086, which is another PAF-antagonist. These results suggest that Y-24180 suppresses IL-5 production through a common pathway which also affects the production of IL-4, even though the mechanism remains to be elucidated as to whether the PAF-antagonistic actions are involved or not.

IL-5: biology and potential therapeutic applications

IL-5 is the predominant cytokine associated with antigen-induced eosinophilic inflammation in the lung. The activation of Th-2 cells leads to the production of IL-5. The pro-eosinophilic effects of IL-5 include: (1) enhanced replication and differentiation of eosinophilic myelocytes; (2) enhanced degranulation of eosinophils; (3) prolonged survival time of eosinophils: and (4) enhanced adhesion of eosinophils. The effects of IL-5 are mediated via the interaction of IL-5 with receptors (IL-5R) that are expressed on the eosinophil cell membrane. Intracellular signalling produced by occupation of the IL-5R by IL-5 occurs via the JAK-STAT system. IL-5 is a 45 kDa glycoprotein consisting of two identical polypeptide chains. The 5'-promoter region of the IL-5 gene contains elements that are down-regulated by glucocorticoids. Anti-IL-5 reagents have the potential to suppress IL-5 activity without the side effects of glucocorticoids. Studies using monoclonal antibodies (mAbs) against IL-5 have established the feasibility of suppressing eosinophilic inflammation by specifically blocking IL-5 activity. Studies with antisense IL-5 are beginning to provide the basis for non-glucocorticoid, sequence-specific oligonucleotide inhibitors of IL-5. Research has begun on the development of mAbs and antisense oligonucleotide inhibitors of IL-5 that can be inhaled and applied topically.

Nonatopic wheezy children have reduced interferon-gamma

Viruses cause asthmatic exacerbations in schoolchildren. We tested the hypothesis that children who wheezed with viral respiratory tract infections secrete higher levels of the type 1 cytokine interferon-gamma (IFN-gamma) in the peripheral circulation than children who had never wheezed. Blood was taken from 13 children (eight atopic) with episodic wheeze and 11 controls. CD4 and CD8 cells were separated from peripheral blood mononuclear cells and stimulated with phorbol 12-myrisate 13-acetate (PMA) and ionomycin for 24 h. IFN-gamma, IL-4, and IL-5 were measured in the supernatant by ELISA. IFN-gamma production by CD4 and CD8 cells was lower in children with a history of wheeze (CD4, P = 0.046; CD8, P = 0.037). These children were then analysed according to atopic status. CD4 and CD8 IFN-gamma production in nonatopic wheezy children was reduced (CD4, P=0.009; CD8, P=0.003). IFN-gamma production by atopic wheezy children was lower than by controls, but the differences were not significant (CD4, P = 0.2831; CD8, P = 0.1372). CD8 IL-5 was lower in children who wheezed (P=0.012). Release of IL-4 and IL-5 by CD4 cells did not differ between the three groups. We propose that defective IFN-gamma secretion by CD4 and CD8 cells may contribute to viral-induced wheeze in nonatopic children.

p38 Mitogen-Activated Protein Kinase Regulates Human T Cell IL-5 Synthesis

Involvement of p38 mitogen-activated protein (MAP) kinase in human T cell cytokine synthesis was investigated. p38 MAP kinase was clearly induced in human Th cells activated through the TCR. SB203580, a highly selective inhibitor of p38 MAP kinase, inhibited the induction of p38 MAP kinase in human Th cells. Major T cell cytokines, IL-2, IL-4, IL-5, and IFN-γ, were produced by Der f 2-specific Th clones upon stimulation through the TCR. IL-5 synthesis alone was significantly inhibited by SB203580 in a dose-dependent manner, whereas the production of IL-2, IL-4, and IFN-γ was not affected. The proliferation of activated T cells was not affected. IL-5 synthesis of human Th clones induced upon stimulation with rIL-2, phorbol ester plus anti-CD28 mAb, and immobilized anti-CD3 mAb plus soluble anti-CD28 mAb was also suppressed by SB203580 in the same concentration response relationship. The results clearly indicated that IL-5 synthesis by human Th cells is dependent on p38 MAP kinase activity, and is regulated distinctly from IL-2, IL-4, and IFN-γ synthesis. Selective control of IL-5 synthesis will provide a novel treatment devoid of generalized immune suppression for bronchial asthma and atopic dermatitis that are characterized by eosinophilic inflammation.

Systemic and local dexamethasone treatments prevent allergic eosinophilia in rats via distinct mechanisms

We have studied the effect of local and systemic treatment with dexamethasone for prevention of the pleural eosinophilia triggered by allergen in actively sensitised Wistar rats. Parallel changes in blood and marrow eosinophil numbers were assessed for comparison. The intrapleural (i.pl.) injection of ovalbumin into ovalbumin-sensitised animals led to a long-lasting pleural fluid eosinophilia which peaked from 24 to 72 h post-challenge. At these time points, there was a significant 2- to 3-fold increase in the blood eosinophil numbers, whereas the bone marrow number of mature eosinophils remained unaltered. Systemic treatment with dexamethasone (0.05-0.5 mg/kg, i.p.) abolished the pleural and blood eosinophilia observed 24 and 48 h post-challenge, also causing a significant reduction in marrow eosinophil numbers. Despite being unable to alter blood and bone marrow eosinophil numbers, the local i.pl. administration of dexamethasone (2.5-10 microg/cavity) inhibited dose dependently the allergen-induced pleural eosinophil influx at 24 h but not at 48 h post-challenge. This treatment also shortened the time course of eosinophil accumulation in the pleural space from the 48 h time point on. We conclude that the effect of systemic but not of local treatment with dexamethasone on allergen-induced eosinophil recruitment is well correlated with the inhibition of eosinophil production in bone marrow. In contrast, low amounts of dexamethasone injected into the pleural space seem to affect locally eosinophil recruitment and survival.

Dexamethasone suppresses gene expression and production of IL-13 by human mast cell line and lung mast cells

BACKGROUND

IL-13 has been shown to induce IgE production in B cells by promoting class switching to IgE. Mast cells are known to play an important role in the pathogenesis of allergic diseases. We evaluated the ability of human mast cells to produce IL-13 using human mast cell line HMC-1 and freshly isolated lung mast cells and then examined the effect of dexamethasone on the gene expression and production of IL-13 by these cells.

METHODS

HMC-1 cells and lung mast cells were cultured with 10 ng/ml phorbol 12-myristate 13-acetate (PMA) and 1 micromol/L ionomycin and with 5 microg/ml phytohemagglutinin (PHA) and 10 ng/ml PMA, respectively, in the presence of dexamethasone. The gene expression of IL-13 at 3 hours (HMC-1 cells) or 12 hours (human lung mast cells) after stimulation was assessed semiquantitatively by sequential reverse transcription-polymerase chain reaction and Southern blot analysis. IL-13 production at 12 hours after stimulation was assayed by ELISA.

RESULTS

The gene expression of IL-13 by HMC-1 cells and human lung mast cells, which was detected at a low level in an unstimulated condition, was increased by PMA/ionomycin and suppressed by dexamethasone. The supernatant of HMC-1 cells and human lung mast cells showed a low level of IL-13, which was increased by the stimulation and suppressed by dexamethasone.

CONCLUSION

These findings indicate that HMC-1 cells and human lung mast cells produce IL-13 and that dexamethasone suppresses the production of IL-13 by these cells through an inhibitory action on the gene expression.

Glucocorticoids inhibit proliferation and interleukin-4 and interleukin-5 secretion by aeroallergen-specific T-helper type 2 cell lines

BACKGROUND

Glucocorticoids play an important role in the treatment of allergic disease. The atopic process, itself, may reduce the response of peripheral blood mononuclear cells (PBMC) to these drugs.

OBJECTIVE

In this study we compared the effect of hydrocortisone (HC), beclomethasone (BDP), and mometasone (MF) on interleukin (IL)-4 and IL-5 secretion by aeroallergen-specific T-helper type 2 cells (Th2) and proliferation of PBMC from atopic donors.

METHODS

Cells were incubated with drug before stimulating with phytohemagglutinin and assessing proliferation (PBMC) and cytokine secretion (Th2).

RESULTS

The glucocorticoids concentration dependently inhibited proliferation and cytokine secretion, but had less effect on proliferation of cells from severe atopics than on cells from those whose symptoms required little treatment. The rank order of potency was MF (average IC50 0.01 nM) > BDP (4.0 nM) > HC (250 nM).

CONCLUSIONS

These experiments demonstrate glucocorticoid inhibition of IL-4 and IL-5 secretion by human Th2-like cells and proliferation of PBMC from severely and mildly allergic donors.

Suppression of gene expression and production of interleukin 13 by dexamethasone in human peripheral blood mononuclear cells

We examined the effect of dexamethasone on the gene expression and production of interleukin (IL)-13 by human peripheral blood mononuclear cells from healthy controls. The gene expression was assessed semiquantitatively by sequential transcription polymerase chain reaction and Southern blot analysis, and the production of this cytokine was assessed by enzyme-linked immunosorbent assay (ELISA). Dexamethasone suppressed IL-13 gene expression induced by stimulation with phytohemagglutinin and phorbol 12-myristate 13-acetate in a dose-dependent manner, with 96% suppression at 10(-6) M, and also suppressed the increased production of IL-13. This is suggested to be one of the mechanisms by which glucocorticoids suppress allergic inflammation.

Difference in inhibitory effects of dexamethasone and cyclosporin A on Sephadex bead-induced airway hyperresponsiveness and inflammation in rats

We investigated the effects of dexamethasone and cyclosporin A on Sephadex bead (Sephadex G-200, Sephadex)-induced airway hyperresponsiveness (AHR) and inflammation in rats. Sephadex (0.5 mg/animal) was intravenously administered on days 0, 2 and 5. Bronchoalveolar lavage, histological study and measurement of AHR were performed on day 7. Dexamethasone (0.1, 1 and 10 mg/kg, p.o. x 3) and cyclosporin A (0.1, 1 and 10 mg/kg, s.c. x 3) clearly inhibited the increase in eosinophils in bronchoalveolar lavage fluid after Sephadex injection. On histological study, pulmonary eosinophilia, granulomatous arteritis with horseshoe-shaped multinuclear giant cell formation and goblet hyperplasia were observed after Sephadex injection. Both dexamethasone (10 mg/kg x 3) and cyclosporin A (10 mg/kg x 3) inhibited these findings and an increase in eosinophil peroxidase in the lung. Dexamethasone dose-dependently inhibited AHR induced by Sephadex, and completely suppressed it at a dose of 1 mg/kg (x 3). Cyclosporin A, however, did not inhibit AHR even at a dose of 10 mg/kg ( x 3). These results show that there is a difference between dexamethasone and cyclosporin A in the inhibitory effect on Sephadex-induced AHR, and they suggest that eosinophils are not directly associated with the development of AHR after Sephadex injection.

Reduced interferon-gamma but normal IL-4 and IL-5 release by peripheral blood mononuclear cells from Xhosa children with atopic asthma

BACKGROUND

Allergic asthma is increasing in black South Africans, a cohort with inherently high basal IgE levels. Atopy has been linked to an excess of the T helper 2 cytokines IL-4 and IL-5 relative to the T helper 1 cytokine interferon-gamma (IFN-gamma); however, most studies have utilized T cell clones. Studies on peripheral blood mononuclear cells (PBMC) have shown decreased IFN-gamma release in patients with atopic dermatitis. It is uncertain whether this finding extends to atopic asthma.

OBJECTIVES

To characterize cytokine release by mitogen-activated PBMC from Xhosa children and to investigate whether reduced IFN-gamma release is a feature of atopic asthma and whether there is a relationship between cytokine profiles and asthma severity.

METHODS

Cytokine release and proliferation of phytohemagglutinin-stimulated PBMC from 10 patients with severe asthma and 14 patients with moderate asthma (highly allergic to house dust mites) and 17 healthy controls was assessed. Total serum, allergen-specific, and Ascaris-specific IgE was measured.

RESULTS

Proliferation did not differ between the groups. The release of IFN-gamma was progressively decreased (and the IL-4/IFN-gamma ratio increased) in the groups with moderate or severe asthma. Tumor necrosis factor-alpha release was reduced, but IL-4, IL-5, and granulocyte-macrophage-colony stimulating factor release was unchanged. The presence of Ascaris-specific IgE did not influence the cytokine profiles.

CONCLUSION

Our study extends the findings observed for other atopic disorders and suggests that defective IFN-gamma release is a generalized feature of atopic diseases. This study-the first to investigate both severe and moderate asthma, with the groups having similar atopic profiles-indicates that the extent of the defect in IFN-gamma release might be related to asthma severity.

RPR 106541, a novel, airways-selective glucocorticoid: effects against antigen-induced CD4+ T lymphocyte accumulation and cytokine gene expression in the Brown Norway rat lung

1. The effects of a novel 17-thiosteroid, RPR 106541, were investigated in a rat model of allergic airway inflammation. 2. In sensitized Brown Norway rats, challenge with inhaled antigen (ovalbumin) caused an influx of eosinophils and neutrophils into the lung tissue and airway lumen. In the lung tissue there was also an accumulation of CD4+ T lymphocytes and increased expression of mRNA for interleukin-4 (IL-4) and IL-5, but not interferon-gamma (IFN-gamma). These findings are consistent with an eosinophilia orchestrated by activated Th2-type cells. 3. RPR 106541 (10-300 microg kg[-1]), administered by intratracheal instillation into the airways 24 h and 1 h before antigen challenge, dose-dependently inhibited cell influx into the airway lumen. RPR 106541 (100 microg kg[-1]) caused a significant (P<0.01) (98%) inhibition of eosinophil influx and a significant (P<0.01) (100%) inhibition of neutrophil influx. RPR 106541 was approximately 7 times and 4 times more potent than budesonide and fluticasone propionate, respectively. 4. When tested at a single dose (300 microg kg[-1]), RPR 106541 and fluticasone each caused a significant (P<0.01) (100%) inhibition of CD4+ T cell accumulation in lung tissue. Budesonide (300 microg kg[-1]) had no significant effect. RPR 106541 and fluticasone (300 microg kg[-1]), but not budesonide (300 microg kg[-1]), significantly (P<0.05) inhibited the expression within lung tissue of mRNA for IL-4. RPR 106541 (300 microg kg[-1]) also significantly (P<0.05) inhibited expression of mRNA for IL-5. 5. The high topical potency of RPR 106541 in this model, which mimics important aspects of airway inflammation in human allergic asthmatics, suggests that this glucocorticoid may be useful in the treatment of bronchial asthma.

Unbalanced production of interleukin-5 and interleukin-2 in children with atopic dermatitis

BACKGROUND

Cytokines, such as interleukin (IL)-5, produced by T helper type 2 Th2) cells appear to play an important role in the inflammatory processes associated with atopic dermatitis. The roles of cytokines produced by Th1 cells remain controversial.

OBJECTIVE

We examined IL-5 and IL-2 mRNA abundance in and protein production by peripheral blood mononuclear cells (PBMCs) from patients with atopic dermatitis and compared those from controls.

METHODS

Peripheral blood mononuclear cells were isolated from six children with atopic dermatitis and six control children, and stimulated with both phytohemaggulutinin (PHA) and phorbol 12-myristate 13-acetate (PMA). The abundance of IL-5 and IL-2 mRNA in PBMCs was measured by reverse transcription-polymerase chain reaction analysis. The production of IL-5 and IL-2 by PBMCs was also determined by enzyme-linked immunosorbent assay.

RESULTS

After incubation with PHA and PMA, PBMCs from atopic children showed significantly higher IL-5 mRNA abundance (P < .05) and IL-5 production (P < .01), as well as a lower amount of IL-2 mRNA (P = .056) and IL-2 production (P < .05) than those from healthy controls. The time course of changes in IL-5 mRNA abundance induced by PHA and PMA in PBMCs from atopic children differed markedly from that observed with healthy controls, whereas the time course of changes in IL-2 mRNA abundance were similar between the two groups.

CONCLUSIONS

The increased IL-5 and decreased IL-2 production observed with PBMCs from children with atopic dermatitis may underlie the activation of eosinophils and high serum immunoglobulin E concentrations also apparent in such individuals. An imbalance in the number and activity of Th1 and Th2 cells is likely to be responsible for the abnormal pattern of cytokine production in atopic dermatitis.

Suppression of the immune system by oral glucocorticoid therapy in bronchial asthma

The effect of systemic glucocorticoid therapy on immune parameters was studied in patients with bronchial asthma. Patients were divided into two groups: 1) those receiving oral glucocorticoid; 2) control patients who did not receive systemic glucocorticoid treatment. The glucocorticoid dose varied between 5 and 70 mg per day. Patients had been taking oral therapy for at least 1 year. Glucocorticoid treatment was associated with an increased frequency of respiratory tract infections. Therefore, we need to define immune parameters which may predict an increased risk of infections. In this study, we analyzed several surface markers on lymphocytes and monocytes by flow cytometry. A significant reduction of the ratio of peripheral blood CD4+ to CD8+ T cells was associated with the administration of oral glucocorticoids. Furthermore, the expression of the HLA-DR molecule on monocytes was reduced in patients with systemic glucocorticoid therapy compared to control patients. Moreover, the capacity to elaborate cytokines by peripheral blood mononuclear cells upon stimulation was greatly reduced after exposure to glucocorticoids in vivo and in vitro. In addition, the humoral immune response was affected, because reduced IgG, IgM, and IgA levels were observed in patients receiving oral glucocorticoids. These results indicate that systemic glucocorticoid treatment in patients with bronchial asthma is associated with cellular and humoral immunosuppression which results in an increased risk of bacterial and viral infections.

Glucocorticoid-mediated inhibition of RANTES expression in human T lymphocytes

The chemokine RANTES has been implicated in the pathogenesis of allergic inflammatory diseases including asthma and rhinitis which are frequently treated with glucocorticoids. We observed that dexamethasone dramatically inhibited RANTES mRNA expression dose dependently in anti-CD3 activated Hut-78 T cells and human PBMCs. Inhibition of RANTES expression did not appear to be secondary to IL-2 inhibition and required binding to the intracellular glucocorticoid receptor. The down-regulation of RANTES expression by glucocorticoids in T cells may directly contribute to the efficacy of these agents in suppressing cellular infiltration and to their anti-inflammatory properties.

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.

How is expression of the interleukin-5 gene regulated?

Eosinophilia is a uniquely specific phenomenon regulated by interleukin-5 (IL-5), suggesting specific control for IL-5 expression. However in eosinophilia IL-5 is often co-expressed with other lymphokines such as IL-4, indicating that common, as well as independent, control mechanisms must exist. IL-5 gene expression is regulated at the transcriptional level. The molecular analysis of the IL-5 promoter region reveals the presence of positive regulatory sites that are common to many lymphokine genes. Results from immunosuppression studies suggest that the key control mechanism of IL-5 regulation may not depend on specific regulatory factors but on how gene expression is activated.

Phosphodiesterase inhibitors suppress proliferation of peripheral blood mononuclear cells and interleukin-4 and -5 secretion by human T-helper type 2 cells

It has been suggested that interleukin-4 and -5 (IL-4 and IL-5) are instrumental in the control of allergic disease. Elevated levels of IL-4 messenger RNA (mRNA) have been detected in numerous foci of atopic activity, including bronchoalveolar lavage (BAL) fluid from atopic asthmatics and skin of atopic dermatitis patients. IL-5 is important in eosinophil activation, which is a common feature of atopic disease. IL-5 mRNA has been detected in BAL fluid from both atopic and non-atopic asthmatics, indicating that IL-5 may be a common feature of the two disease states. Production of IL-4 and IL-5 by T cells appears to be associated with a high affinity cyclic AMP (cAMP) phosphodiesterase (PDE). This study was designed to compare the effects of PDE inhibitors Ro20-1724 and theophylline on (1) the mitogenic response of peripheral blood mononuclear cells from atopic and non-atopic individuals and (2) secretion of IL-4 and IL-5 by TH(2) cells after activation with PMA and anti-CD3. Both Ro20-1724 and theophylline inhibited proliferation of PBMC in a dose-dependent manner. There was no significant difference between proliferation of PBMC from atopic versus non-atopic donors, but Ro20-1724, a specific PDE IV inhibitor, was more potent at a concentration of 10(-5)M than theophylline in suppressing lymphocyte proliferation. Similarly, both PDE inhibitors suppressed secretion of IL-4 and IL-5 from TH(2)-like cell lines in a dose-dependent manner. In conclusion, as Ro20-1724 and theophylline inhibit proliferation of PBMC and secretion of IL-4 and IL-5 from human TH(2) cell lines, the development of a selective cyclic nucleotide PDE IV inhibitor may provide a promising new approach for asthma prophylaxis.

Production of interleukin-5 and the suppressive effect of cyclosporin A in childhood severe atopic dermatitis

A child with severe atopic dermatitis had marked improvement with oral cyclosporin A (CyA) therapy. The function of activated T lymphocytes and serum interleukin-5 concentrations were reduced. The expression and production of interleukin-5 were high, but were suppressed during CyA therapy and by CyA in vitro. Oral CyA therapy may be useful for severe atopic dermatitis.

Cytokine production by phytohemagglutinin-stimulated human blood cells: effects of corticosteroids, T cell immunosuppressants and phosphodiesterase IV inhibitors

The ability of dexamethasone and prednisolone (corticosteroids), FK506 and cyclosporin A (T cell immunosuppressants), and of nitraquazone and rolipram (phosphodiesterase IV inhibitors) to inhibit cytokine production by stimulated human blood was investigated. Heparinized human blood obtained from normal healthy volunteers was stimulated with phytohemagglutinin (PHA) in the presence or absence of drug. After different incubation times, supernatant levels of interleukin (IL)-2, IL-5, granulocyte-macrophage colony stimulating factor (GM-CSF) and interferon gamma (IFN-gamma) were quantified by ELISA. Dexamethasone strongly inhibited the production of IL-5 (IC50 = 0.004 microM), was less potent against IL-2 and IFN-gamma (IC50 = 0.02-0.05 microM) and showed a relatively weak effect against GM-CSF (IC50 = 0.6 microM). Similarly prednisolone potently suppressed IL-5 generation (IC50 = 0.05 microM), displayed a more modest activity on IL-2 and IFn-gamma (IC50 = 0.2-0.3 microM) and exerted only partial effects (43% inhibition at 1 microM) on GM-CSF). FK506 strongly suppressed the production of IL-2 (IC50 = 0.01 microM) and GM-CSF (IC50 = 0.03 microM), but was inactive (< 30% inhibition at 1 microM) against IL-5 and IFN-gamma. Similarly, cyclosporin A reduced the generation of IL-2 (IC50 = 0.4 microM) and GM-CSF (IC50 = 0.6 microM) while barely affecting the other two cytokines. Nitraquazone and rolipram were most active in reducing the production of IL-5 (IC50 = 0.8 and 1.3 microM, respectively), while their potency against IL-2, GM-CSF and IFN-gamma was 3-6 times lower, with IC50's between 2.4 and 8.0 microM. These data indicate that corticosteroids, T cell immunosuppressants and phosphodiesterase IV inhibitors affect cytokine production by PHA-stimulated human blood cells in a differential and "pharmacotypical'' manner.