Dysregulation of interleukin 4, interleukin 5, and interferon gamma gene expression in steroid-resistant asthma

Lidocaine and its Analogues Inhibit IL-5-Mediated Survival and Activation of Human Eosinophils

Eosinophils and cytokines active on eosinophils, especially IL-5, are believed to be critically involved in chronic allergic diseases. IL-5 activates eosinophils and enhances their survival in vitro by delaying apoptosis. In this study, we found that lidocaine and six analogues blunt responses of eosinophils to IL-5. Lidocaine and its derivatives inhibit IL-5-mediated eosinophil survival in a concentration-dependent manner (IC50 = 110 μM for 30 pg/ml IL-5). At suboptimal lidocaine concentrations, the eosinophil survival response to IL-5 shifts and more IL-5 is required to maintain survival. The inhibitory effect requires at least 24-h exposure of eosinophils to lidocaine, and the protein kinase C activator, PMA, completely reverses the inhibition. A multiparameter flow-cytometric analysis shows that lidocaine hastens the apoptosis of eosinophils normally delayed by IL-5. Lidocaine does not affect IL-5R expression or IL-5-induced protein tyrosine phosphorylation. Lidocaine also inhibits eosinophil survival mediated by IL-3 or granulocyte-macrophage CSF, although less potently than that mediated by IL-5. Furthermore, lidocaine inhibits eosinophil superoxide production stimulated by IL-5, granulocyte-macrophage CSF, or IL-3, but not that stimulated by platelet-activating factor, immobilized IgG, or PMA. Lidocaine and its derivatives show novel immunomodulatory properties and are able to blunt eosinophil responses to cytokines in addition to their local anesthetic or antiarrhythmic properties. Thus, lidocaine and its derivatives may represent a new class of therapeutic agents to treat patients with allergic diseases.

Brittle asthma

We believe that the asthma phenotypes we have defined as types 1 and 2 brittle asthma appear to be defined subgroups of asthma. For example, we have characterised patients with type 1 brittle asthma, as defined in this review, on the basis of peak flow variability and treatment and these patients remain a separate group when assessed by other means such as psychosocial factors, immunoglobulin levels, and atopy. The question remains as to whether they are truly separate groups with entirely different pathogenetic influences or whether they simply represent the severe end of the spectrum. Our suggested classification into types 1 and 2 forms a useful start for studies of this condition, although prospective evaluation of patients with severe asthma is the only way of substantiating the validity of these definitions which will then enable investigation of possible mechanisms. However, these patients are rare and in order to study them as a group a national register would need to be set up along the lines of the West Midlands Brittle Asthma Register, perhaps recruiting all "at risk" patients and then using this resource as a means of exploring the different asthma phenotypes within this broad grouping, including brittle asthma.

Corticosteroids Enhance the Capacity of Macrophages to Induce Th2 Cytokine Synthesis in CD4+ Lymphocytes by Inhibiting IL-12 Production

We investigated the effects of corticosteroids on IL-12 production by mouse splenic adherent cells and the subsequent capacity of these cells to induce cytokine production by CD4+ T cells. To distinguish the effects of corticosteroids on APCs from those on T cells, only the APCs and not the T cells were exposed to corticosteroids. Treatment of splenic adherent cells with dexamethasone greatly inhibited production of IL-12, a cytokine known to enhance IFN-γ synthesis and decrease IL-4 synthesis by CD4+ T cells. The reduction in IL-12 production by corticosteroid-treated macrophages decreased their ability to induce IFN-γ and increased their ability to induce IL-4 synthesis in Ag-primed CD4+ T cells. Splenic adherent cells from mice treated in vivo with dexamethasone also displayed a reduced capacity to produce IL-12. These results help to resolve previous conflicting observations regarding the effects of corticosteroids on cytokine production by T cells, and indicate that while corticosteroids may directly inhibit Th1 and Th2 cytokine production in T cells, corticosteroids, by reducing IL-12 production in APCs, have the potential to indirectly enhance Th2 cytokine synthesis. Therefore, treatment of diseases such as allergy with chronic corticosteroids may indirectly exacerbate the course of the disease, which is caused primarily by the overproduction of Th2 cytokines in allergen-specific CD4+ T cells.

Molecular basis of allergic diseases

This review examines our current understanding of the mechanisms underlying allergic diseases. The IgE molecule plays a central role in the pathogenesis of immediate hypersensitivity reactions by virtue of its capacity to bind specifically to high-affinity IgE receptors on mast cells and mediate the release of various mast cell-derived mediators and proinflammatory cytokines on exposure to allergen. Clinically significant allergic responses are followed by a late-phase response dominated by eosinophils and T lymphocytes. The majority of T cells in allergic responses are memory T cells secreting helper type 2 (TH2)-like cytokines, i.e., interleukin (IL)-4, IL-5, IL-13, but not interferon-gamma. These cytokines regulate IgE synthesis and promote eosinophil development, thus contributing to allergic inflammatory responses. Failure to control immune activation early in the course of allergic disease blunts responses to glucocorticoid therapy and contributes to disease progression. The identification of key cells and molecules involved in the initiation and maintenance of allergic inflammation is likely to become an important target in the treatment of this common group of illnesses.

New directions in understanding interleukin-5 gene expression

Specific regulation of the interleukin-5 (IL-5) gene is implied by the unique control of eosinophilia which is regulated by IL-5. In studies of IL-5 gene expression, the only control elements identified for the IL-5 gene have been transcriptional elements in the 5' untranslated region (UTR). Significant differences exist in the arrangement of the murine and human IL-5 promoters, which is surprising considering the tight regulation of the gene. Novel palindromic regulatory elements involved in transcriptional regulation have been found in the 5' UTR and new results show the presence of transcriptional elements in the 3' UTR. Post-transcriptional control mechanisms in both the 5' and 3' UTRs have also been described.

New insights into steroid resistant asthma

The term "steroid resistant (SR) asthma" refers to a group of asthmatics who have persistent airway obstruction and immune activation despite treatment with high doses of systemic glucocorticoids. There are at least two forms of SR asthma, i.e. primary and acquired types. Type I SR asthma is acquired and is associated with abnormally reduced glucocorticoid receptor (GCR) ligand and DNA binding affinity. Type II SR asthma appears to be due to a constitutive defect and is associated with low numbers of GCRs. An important distinction between these two types of SR asthma is that the GCR defect in Type I, but not Type II, SR asthma is reversible in culture and is sustained by incubation with combination IL-2 and IL-4. Recent studies suggest that the abnormal GCR binding in Type I SR asthma may be due to cytokine-driven alternative splicing of the GCR pre-mRNA to a novel isoform called GCRbeta which does not bind glucocorticoids but antagonizes the transactivating activity of the classic GCR. These GCR changes along with recent evidence for increased transcription factor activation in SR asthma which may inhibit GCR/DNA interactions as well as the selective recruitment of neutrophils into the airways of certain patients with severe asthma contribute to the heterogeneity of mechanisms underlying steroid resistance.

Effects of dexamethasone on the profile of cytokine secretion in human whole blood cell cultures

EXPERIMENTAL OBJECTIVES

The interaction between the endocrine and immune systems is a very intriguing area. Endogenous glucocorticoids, as end-effectors of the hypothalamo-pituitary-adrenal axis, inhibit the immune and inflammatory responses and are used as immunosuppressive drugs in many inflammatory, autoimmune and allergic diseases. The aims of this study were to investigate the effects of dexamethasone on the profile of cytokine secretion in whole blood cell cultures from healthy subjects and to analyse the gender-related sensitivity to dexamethasone on each cytokine secretion.

RESULTS

There was a significant inhibition by dexamethasone (from 1 to 100 nM) on the secretion of monokines (IL-1beta, IL-6, IL-8 and TNF alpha) and lymphokines (IL-2, IL-4, IL-10 and IFN gamma), either after LPS or PHA stimulation (P < 0.01). Interleukin 4 and IL-10 were less inhibited than IFN gamma (P < 0.05 at 1 nM, P < 0.01 at 10 nM and P < 0.001 from 100 nM to 10 microM). No gender difference was observed in the rate of inhibition of the secretion of each cytokine.

CONCLUSION

This study shows that the inhibition of cytokine secretion by dexamethasone is more marked on Th1-type cytokines than on Th2-type cytokines. These data support the idea that glucocorticoids may induce a shift from the Th1 to Th2 profile of cytokine secretion.

Association of glucocorticoid insensitivity with increased expression of glucocorticoid receptor beta

In many chronic inflammatory disorders, glucocorticoid (GC) insensitivity is a challenging clinical problem associated with life-threatening disease progression. The molecular basis of GC insensitivity, however, is unknown. Alternative splicing of the GC receptor (R) pre-messenger RNA generates a second GCR, termed GCR-beta, which does not bind GCs but antagonizes the transactivating activity of the classic GCR, termed GCR-alpha. In the current study, we demonstrate that GC-insensitive asthma is associated with a significantly higher number of GCR-beta-immunoreactive cells in peripheral blood than GC-sensitive asthmatics or normal controls. Furthermore, we show that patients with GC-insensitive asthma have cytokine-induced abnormalities in the DNA binding capability of the GCR. These abnormalities can be reproduced by transfection of cell lines with the GCR-beta gene resulting in significant reduction of their GCR-alpha DNA binding capacity. We conclude that increased expression of GCR-beta is cytokine inducible and may account for GC insensitivity in this common inflammatory condition.

Immunologic basis of chronic allergic diseases: clinical messages from the laboratory bench

During the past decade there have been significant advances in our understanding of the mechanisms underlying allergic responses. Immediate hypersensitivity reactions are mediated primarily by mast cells in an IgE-dependent manner. After the local release of various mediators, proinflammatory cytokines, and chemokines, there is a cell-mediated response that is dominated by eosinophils and T lymphocytes. The majority of T cells in early allergic reactions are memory T cells secreting helper type 2 (TH2)-like cytokines, i.e. IL-4, IL-5, and IL-13, but not interferon-gamma. These cytokines regulate IgE synthesis and promote eosinophil differentiation and cell survival, thus contributing to allergic inflammatory responses. Failure to control immune activation early in the course of allergic inflammation may blunt the response to glucocorticoid therapy and contribute to long-term morbidity of disease. The identification of key cells and cytokines involved in the initiation and maintenance of allergic inflammation is likely to become an important therapeutic target in the future management of this important group of diseases.

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.

Interleukin-2 and -4 induce resistance of granulocyte-macrophage colony-stimulating factor to corticosteroids

In vitro pretreatment of human mononuclear blood cells with a combination of interleukin-2 and interleukin-4 decreases corticosteroid receptor affinity and reduces the anti-proliferative effects of corticosteroids. Similar abnormalities have been observed in mononuclear blood cells of steroid-resistant asthmatics. In vitro steroid resistance was induced by 48 h pretreatment of mononuclear blood cells from healthy individuals (n = 10) with interleukin-2 and interleukin-4 (500 Units (U)/ml). The effects of three structurally different corticosteroids (10(-7)-10(-11) M) on lipopolysaccharide-stimulated (10 ng/ml; 20 h) production of granulocyte-macrophage colony-stimulating factor (GM-CSF) were examined. GM-CSF production was efficiently inhibited by all three corticosteroids in the control cultures. Cortivazol was significantly more potent (IC50 = 3 x 10(-11) M) than budesonide and tipredane (IC50 = 2.5 x 10(-10) M and IC50 = 2 x 10(-10) M, respectively). However. interleukin-2 and interleukin-4 pretreatment counteracted the inhibitory effects of all three corticosteroids to a similar degree. The results highlight the importance of interleukin-2 and interleukin-4 in the induction of steroid resistance, since pretreatment of mononuclear blood cells with these cytokines impaired corticosteroid inhibition of GM-CSF production.

Diagnosis and management of steroid-resistant asthma

The term "steroid-resistant (SR) asthma" has been used to describe a group of asthmatics who demonstrate persistent airway obstruction and inflammation despite treatment with high doses of systemic glucocorticoids. There are at least two forms of SR asthma, that is, primary and acquired types. Type I SR asthma is acquired and is associated with abnormally reduced glucocorticoid receptor (GR) ligand and DNA binding affinity. Type II SR asthma is due to a primary GR binding abnormality. An important distinction between these two types of SR asthma is that the GR defect in Type I, but not Type II, SR asthma is reversible in culture and is sustained by incubation with combination IL-2 and IL-4. The treatment of these patients requires a systematic approach to rule out confounding factors, including triggers of immune activation, optimizing steroid therapy, and use of alternative strategies to inhibit airway inflammation.

Increased expression of interleukin-16 in bronchial mucosa of subjects with atopic asthma

Asthma is characterized by the presence of activated CD4+ cells in the airways. We hypothesized that the newly characterized cytokine interleukin (IL)-16 is involved in the pathogenesis of asthma through its ability to selectively induce CD4+ cell recruitment within the inflamed bronchial wall. We investigated the expression of IL-16 in bronchial biopsies obtained from subjects with mild asthma (n = 10), atopic nonasthmatic individuals (n = 6), and normal control subjects (n = 10). Cryostat sections from 4% paraformaldehyde-fixed fiberoptic bronchial biopsies were immunostained using a specific antibody that recognizes human IL-16. IL-16 mRNA expression was determined by in situ hybridization. IL-16 immunoreactivity and mRNA were demonstrated mainly in bronchial epithelial cells in all subjects. IL-16 immunoreactivity and IL-16 mRNA expression within the epithelium were significantly higher in bronchial biopsies obtained from asthmatic subjects as compared to both atopic nonasthmatic and normal controls (P < 0.001). The numbers of subepithelial IL-16 immunoreactive cells and IL-16 mRNA-positive cells were also greater in the bronchial biopsies obtained from asthmatic subjects as compared to both atopic nonasthmatic and normal controls (P < 0.001). Epithelial expression of IL-16 immunoreactivity and mRNA correlated with the CD4+ cell infiltration (r2 = 0.70, P < 0.001). There were significant associations between epithelial and subepithelial IL-16 immunoreactivity and airway responsiveness to methacholine. This study demonstates that IL-16 is expressed in airway tissues, particularly in the epithelial cells, and that up-regulation of its expression is a feature of allergic asthma. These results suggest an in vivo role for IL-16 in the pathogenesis of asthma, possibly through the recruitment of CD4+ cells, and support the increasing evidence for the participation of epithelial cells in regulating inflammatory responses.

Response to intranasal fluticasone propionate in perennial allergic rhinitis not associated with glucocorticoid receptor characteristics

BACKGROUND

The reduction of symptoms due to treatment with corticosteroids varies among patients with perennial rhinitis. Most patients will respond but a few patients respond less to these drugs.

OBJECTIVE

To investigate the association in reduction of symptoms due to glucocorticoids and glucocorticoid receptor characteristics in patients with perennial allergic rhinitis, in vitro glucocorticoid receptor binding studies were performed with peripheral blood mononuclear cells using dexamethasone and in vitro production of mediators were measured.

METHODS

During a double-blind placebo-controlled crossover study, 200 micrograms fluticasone propionate aqueous nasal spray (in the active treatment period) and placebo (in the placebo treatment period) were administered twice daily for 2 weeks to 22 patients allergic to house dust mite. At the end of both treatment periods symptoms were scored after allergen provocation (100, 1000, 10000 BU/mL) and during the 9.5 hours after this challenge. Receptor binding studies with dexamethasone were performed with peripheral blood mononuclear cells. Leukotriene B4 produced by monocytes in vitro and soluble interleukin-2 receptor released by lymphocytes in vitro and cortisol levels in plasma were determined.

RESULTS

No significant partial correlations of the number of the peripheral blood mononuclear cell glucocorticoid receptors (6821 +/- 5669 binding sites per cell) and the affinity (Kd: 16.5 +/- 13.51 nmol/L) for the glucocorticoid receptors with the symptom score (placebo: 4.3 +/- 2.45 pts; fluticasone: 2.4 +/- 1.55 pts) after active treatment were found. Also no significant partial correlations of the levels of leukotriene B4 (45.6 +/- 105.3 ng/10(6) cells) produced by monocytes in vitro, soluble interleukin-2 receptor (734 +/- 237 ng/10(6) cells) released by lymphocytes in vitro and cortisol levels (571 +/- 236 ng/mL) in plasma with the symptom score after active treatment were found.

CONCLUSIONS

The reduction of symptoms due to topical fluticasone propionate in patients with rhinitis and allergy to house dust mite is not correlated with the characteristics of the glucocorticoid receptor.

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.

Evaluation of non-steroidal ointment therapy for adult type atopic dermatitis: inquiry analysis on clinical effect

Clinical analysis was performed on non-steroidal ointment therapy for 70 patients with refractory adult-type atopic dermatitis by the clinical data and patient's own evaluation of the therapy obtained through enquiries after discharge from the hospital. Forty cases (57%) were between 20 and 30 years old and the male and female ratio was 39/31. The clinical evaluations were subdivided into five groups; conditions worsened (n = 9), no-change (n = 9), slightly improved (n = 14), much improved (n = 29) and cured (n = 9). Although statistically not significant, the age of onset of atopic dermatitis and the start of use of steroid ointment was much higher while the duration of the atopic dermatitis was much shorter in the remission patients. The duration of steroid ointment therapy for the facial skin was significantly shorter in the remission group when compared to groups with worsened symptoms and no-change in symptoms. Family history and complications of atopic diseases, laboratory data including IgE titer, eosinophils and RAST score were not statistically significant in any group except for a higher prevalence of IgE antibodies against inhalant and food allergens in the group with worsened symptoms. Most patients still used steroid ointment on the trunk lesions while they ceased using from the topical steroid on the facial lesions after discharge. Most frequent precipitating factors pointed out by the patients were emotional stress, irritation by sweat or UV light and longstanding use of steroid ointment. Complications of cataracta and retinopathy were found in 12 cases. These results suggest that remission of adult-type refractory atopic dermatitis can be achieved by the combination of careful daily skin care, use of non-steroidal topical ointment and minimizing the precipitating factors.

Bronchoalveolar lavage in asthma research

A great deal of information about the pathophysiology of asthma and its treatment have been obtained through the use of bronchoalveolar lavage (BAL), especially in combination with airway biopsies. The introduction of highly sophisticated methods for examining BAL aspirate, including fluorocein activated cell scanning (FACS) analysis and molecular biology techniques has emphasized the potential power of this method of airway investigation. For those contemplating the use of BAL in asthma research programmes, we hope that this review will provide a useful insight into the current state of knowledge about the technique and its application, and that it will provide a solid platform for study design.

Steroid-resistant asthma: evaluation and management

LEARNING OBJECTIVES

Reading this article will reinforce the reader's knowledge of the definition, pathophysiology, differential diagnosis, and treatment of the steroid-resistant asthmatic patient.

DATA SOURCES

Prospective and retrospective data from the authors' experience were evaluated. In addition, a Medline database was searched from 1981, using the key words "asthma," "glucocorticoids," and "glucocorticoid resistance" with the restrictions of English language and human subjects. Relevant articles referenced in retrieved sources and current texts on severe asthma were also utilized.

STUDY SELECTION

Data source abstracts, pertinent articles, and book chapters meeting the objectives were critically reviewed.

RESULTS

Although rare, individuals with steroid-resistant asthma are often the most difficult-to-manage asthmatic patients in that they have severe disease yet fail to respond to glucocorticoids. To make the diagnosis of steroid-resistant asthma, the patient must fail to respond to a 7 to 14-day course of daily prednisone as measured by less than a 15% improvement in morning prebronchodilator FEV1 following the glucocorticoid course. Ongoing inflammation is thought to play a major role in the pathogenesis of steroid-resistant asthma, and recent studies have demonstrated diminished glucocorticoid receptor to glucocorticoid, or diminished glucocorticoid receptor to DNA binding as possible mechanisms for diminished glucocorticoid responsiveness. Alternative asthma therapies such as methotrexate, cyclosporine, and intravenous gammaglobulin are often used in this group of asthmatic patients.

CONCLUSIONS

The patient with steroid-resistant asthma presents several challenges. These individuals often display many of the sequelae of long-term systemic glucocorticoid use while achieving little therapeutic benefit. Prior to making the diagnosis of steroid-resistant asthma, diseases that can contribute to poor control of asthma must be ruled out, and noncompliance issues addressed. Alternative asthma therapies are often used; however, they also carry the potential for adverse effects, and have not been thoroughly studied in this population of asthmatic patients.

Type 1 and type 2 cytokine dysregulation in human infectious, neoplastic, and inflammatory diseases

In the mid-1980s, Mosmann, Coffman, and their colleagues discovered that murine CD4+ helper T-cell clones could be distinguished by the cytokines they synthesized. The isolation of human Th1 and Th2 clones by Romagnani and coworkers in the early 1990s has led to a large number of reports on the effects of Th1 and Th2 on the human immune system. More recently, cells other than CD4+ T cells, including CD8+ T cells, monocytes, NK cells, B cells, eosinophils, mast cells, basophils, and other cells, have been shown to be capable of producing "Th1" and "Th2" cytokines. In this review, we examine the literature on human diseases, using the nomenclature of type 1 (Th1-like) and type 2 (Th2-like) cytokines, which includes all cell types producing these cytokines rather than only CD4+ T cells. Type 1 cytokines include interleukin-2 (IL-2), gamma interferon, IL-12 and tumor necrosis factor beta, while type 2 cytokines include IL-4, IL-5, IL-6, IL-10, and IL-13. In general, type 1 cytokines favor the development of a strong cellular immune response whereas type 2 cytokines favor a strong humoral immune response. Some of these type 1 and type 2 cytokines are cross-regulatory. For example, gamma interferon and IL-12 decrease the levels of type 2 cytokines whereas IL-4 and IL-10 decrease the levels of type 1 cytokines. We use this cytokine perspective to examine human diseases including infections due to viruses, bacteria, parasites, and fungi, as well as selected neoplastic, atopic, rheumatologic, autoimmune, and idiopathic-inflammatory conditions. Clinically, type 1 cytokine-predominant responses should be suspected in any delayed-type hypersensitivity-like granulomatous reactions and in infections with intracellular pathogens, whereas conditions involving hypergammaglobulinemia, increased immunoglobulin E levels, and/or eosinophilia are suggestive of type 2 cytokine-predominant conditions. If this immunologic concept is relevant to human diseases, the potential exists for novel cytokine-based therapies and novel cytokine-directed preventive vaccines for such diseases.

A strict requirement of interleukin-4 for interleukin-4 induction in antigen-stimulated human memory T cells

The role of interleukin-4 (IL-4) in the induction of IL-4 in mouse T cells is well established, but conflicting results have been reported with anti-CD3-primed human T cells and T cell clones. Therefore, IL-4 regulation was investigated in short-term cultured human T cells primed in vitro with either a superantigen or a hapten, nickel sulfate (NiSO4), for 3 days and expanded with IL-2 for another 5 days. Under these conditions, antigen-specific IL-4 producing T cells were generated in 35/40 cultures. Priming for IL-4 production was abrogated in all cultures by anti-IL-4 antibody or soluble IL-4 receptor (sIL-4R). Primed T cells that were IL-4- when cultured with IL-2 only developed an IL-4 producing phenotype when primed and expanded in the presence of exogenous IL-4. T cells primed in the presence of either endogenous or exogenous IL-4 produced 10-200-fold more IL-4 than T cells primed in the presence of anti-IL-4 antibody or sIL-4R. While IL-4 induction was absolutely dependent on IL-4, neither endogenous nor exogenous IL-4 influenced IFN-gamma synthesis. Most importantly, IL-4 induced and sIL-4R abolished priming for IL-4 production even in NiSO4-specific memory T cells from sensitized individuals. Thus, IL-4 induction in antigen-specific human memory T cell populations absolutely required IL-4. The IL-4 pathway of memory T cells retained a remarkable plasticity in sensitized individuals.

Glucocorticoid-resistant asthma. T-lymphocyte defects

There is adequate evidence that clinical glucocorticoid resistance in asthma can be attributed at least partly to a relative resistance of T cells to inhibition by glucocorticoids. Although GR asthma defined according to the present criteria represents one end of a spectrum of clinical response, in clinical practice these patients would not be exposed for prolonged periods to dosages of glucocorticoids sufficient to inhibit their T cells in vivo. A more rational approach to the selection of alternative therapy for such patients might be possible when the mechanisms of this resistance are identified. In the meantime, there is some justification for assessing other drugs that inhibit T cells from patients with GR asthma at therapeutic concentrations for their efficacy and risk/benefit ratios in clinical practice.

Pathology of rhinitis and bronchial asthma

Studies of the pathology of rhinitis and asthma have identified similarities and differences between these two clinical conditions. With regard to symptoms, both the nose and the lower airways respond to neural stimulation by irritant substances, but a major difference is that engorgement of the capacitance vessels is the main cause of nasal obstruction in rhinitis, while muscle constriction is the major determinant of lower airway narrowing. There are also similarities and differences with respect to the role of inflammatory cells. In both conditions there is evidence of allergen-induced mast cell activation, with production of an array of mediators (some mast cell-derived and others originating from a variety of other cell types). Eosinophilia is also characteristic of both diseases--it is prominent even in mild forms of asthma, but is low in pollen-sensitive rhinitics outside of the season. T-cell activation and production of cytokines plays an important role in the development and maintenance of allergic disease, but the level of T-cell activation may differ between asthma and rhinitis. Further research into differences in cellular activity and response to treatment between these two diseases may help define factors which will determine whether atopic disease is expressed in the upper, lower, or both parts of the respiratory tract.

Role and modulation of T-cell cytokines in allergy

Allergic sensitization and the development of effector functions are controlled by IL-4-secreting and IL-5-secreting type 2 T cells. Recent studies have provided new insights into the events triggering the development of type 1 and type 2 T cells, the discrimination of type 1 and type 2 effector T cells from various T-cell subsets, and the improvement of established and new therapeutic strategies, which are aimed at modulating such T-cell functions in the allergic patient.

Altered Th1/Th2 cytokine profiles in the intestinal mucosa of patients with inflammatory bowel disease as assessed by quantitative reversed transcribed polymerase chain reaction (RT-PCR)

Cytokines serve a central function as key factors in the regulation of the intestinal immune response and mediation of tissue damage in inflammatory bowel disease (IBD). Abnormalities in the expression of immunoregulatory cytokines such as IL-2, IL-4, IL-10 and interferon-gamma (IFN-gamma) may indicate a dysregulation of intestinal immunity probably associated with pathogenic events. Therefore, cytokine mRNA concentrations were determined in the mucosa of patients with IBD at sites of active (n = 13) and inactive (n = 12) ulcerative colitis (UC), active (n = 11) and inactive (n = 11) Crohn's disease (CD) and in control patients (n = 14) using quantitative RT-PCR. IL-10 mRNA concentrations were significantly increased in patients with both active UC (P < 0.001) and active CD (P < 0.005) compared with control patients. IFN-gamma mRNA concentrations were also significantly increased both in patients with active UC (P < 0.02) and active CD (P < 0.05) compared with control patients, whereas IL-2 mRNA levels were significantly (P < 0.02) increased only in active CD. IL-4 mRNA expression in the intestinal mucosa was frequently below the detection limit. Our results demonstrate that chronic intestinal inflammation in patients with CD is characterized by an increase of Th1-like cytokines. Furthermore, the increased IL-10 mRNA expression at sites of active IBD suggests that IL-10 is an important regulatory component involved in the control of the inflammatory response in inflammatory bowel disease.