Interleukin-4 and interleukin-5 are rarely co-expressed by human T cells

Anti-human Interleukin(IL)-4 Clone 8D4-8 Cross-Reacts With Myosin-9 Associated With Apoptotic Cells and Should Not Be Used for Flow Cytometry Applications Querying IL-4 Expression

Interleukin(IL)-4 is produced by T cells and other leukocytes and is a critical mediator of monocyte and B cell responses. During routine flow cytometry panel validation for the investigation of intracellular cytokines, we observed unique IL-4 expression patterns associated with the widely available monoclonal antibody 8D4-8. Namely, IL-4 (8D4-8) expression was observed in the absence of cellular activation and enhanced following staurosporine exposure. Mass spectrometry analysis of immunoprecipitates from peripheral blood lymphocytes (PBL) revealed that 8D4-8 cross-reacts with the ubiquitous cytoskeletal protein myosin-9. We confirmed these results by western blotting immunoprecipitates, using immunofluorescence among staurosporine-treated Caco-2 cells, and by surface-labeling PBL for 8D4-8 and myosin-9 and analyzing by flow cytometry. Although previously reported from several independent groups, we found no evidence to support the hypothesis that IL-4 is produced by apoptotic cells. Rather, this appears to have been myosin-9. Our data indicate clone 8D4-8 should not be used in the flow cytometric study of IL-4. Furthermore, our work calls for a reevaluation of previous flow cytometric studies that have used this clone for IL-4 analysis and highlights the importance of validation in antibody-based assays.

Density-dependent effects of Caligus rogercresseyi infestation on the immune responses of Salmo salar

Sea lice infestations are a particular concern in the salmonid aquaculture industry due to damaging effects on fish growth, disease/infection susceptibility, and survival. Despite the impacts of sea lice parasitism, few studies have determined corresponding physiological thresholds, or the quantity of sea lice that can trigger measurable effects in the host immune response. The present study evaluated the mRNA expressions of immune-related genes in Salmo salar (Atlantic salmon) under infestation challenges with contrasting loads of the sea louse Caligus rogercresseyi. Specifically, two groups of S. salar were infected with either 35 (i.e. low parasitic load) or 100 (i.e. high parasitic load) copepodids per fish. At 14 days post-infestation, the mRNA levels of immune-related genes (e.g. related to oxidative stress, pro- and inflammatory responses, and the adaptive T_H1/T_H2 pathways) were assessed through RT-qPCR. Significant differences were found in relation to parasitic load, suggesting density-dependent effects that activated the S. salar immune system. Higher parasitic load promoted strong inflammatory and oxidative stress responses that were correlated with the T_H1 immune response. This study highlights the molecular signatures for distinct parasitic loads, providing new perspectives towards fully understanding parasite-host interactions.

Cytokine diversity in the Th1-dominated human anti-influenza response caused by variable cytokine expression by Th1 cells, and a minor population of uncommitted IL-2+IFNγ- Thpp cells

Within overall Th1-like human memory T cell responses, individual T cells may express only some of the characteristic Th1 cytokines when reactivated. In the Th1-oriented memory response to influenza, we have tested the contributions of two potential mechanisms for this diversity: variable expression of cytokines by a uniform population during activation, or different stable subsets that consistently expressed subsets of the Th1 cytokine pattern. To test for short-term variability, in vitro-stimulated influenza-specific human memory CD4+ T cells were sorted according to IL-2 and IFNγ expression, cultured briefly in vitro, and cytokine patterns measured after restimulation. Cells that were initially IFNγ+ and either IL-2+ or IL-2- converged rapidly, containing similar proportions of IL-2-IFNγ+ and IL-2+IFNγ+ cells after culture and restimulation. Both phenotypes expressed Tbet, and similar patterns of mRNA. Thus variability of IL-2 expression in IFNγ+ cells appeared to be regulated more by short-term variability than by stable differentiated subsets. In contrast, heterogeneous expression of IFNγ in IL-2+ influenza-specific T cells appeared to be due partly to stable T cell subsets. After sorting, culture and restimulation, influenza-specific IL-2+IFNγ- and IL-2+IFNγ+ cells maintained significantly biased ratios of IFNγ+ and IFNγ- cells. IL-2+IFNγ- cells included both Tbet^lo and Tbet^hi cells, and showed more mRNA expression differences with either of the IFNγ+ populations. To test whether IL-2+IFNγ-Tbet^lo cells were Thpp cells (primed but uncommitted memory cells, predominant in responses to protein vaccines), influenza-specific IL-2+IFNγ- and IL-2+IFNγ+ T cells were sorted and cultured in Th1- or Th2-generating conditions. Both cell types yielded IFNγ-secreting cells in Th1 conditions, but only IL-2+IFNγ- cells were able to differentiate into IL-4-producing cells. Thus expression of IL-2 in the anti-influenza response may be regulated mainly by short term variability, whereas different T cell subsets, Th1 and Thpp, may contribute to variability in IFNγ expression.

T cells specific to leishmania and other nonrelated microbial antigens can migrate to human leishmaniasis skin lesions

Immunopathological studies have contributed to the characterization of in situ inflammatory infiltrates in cutaneous leishmaniasis (CL). However, little is known about the T-cell antigen reactivity of these lesions. Our objective was to analyze the responsiveness of lymphocytes from CL lesions to leishmanial and nonrelated antigens in terms of proliferation and the production of cytokines. Mononuclear cells were extracted from lesions, and blood from CL patients infected with Leishmania (Viannia) braziliensis. Activated cells accounted for 35-45% of lesions T-cell subsets. Elevated levels of C1.7/CD244(+)CD8(+) T cells suggest in situ cytotoxic effector function. Lymphocytes isolated from the leishmaniasis lesions proliferated and produced IFN-gamma in response to leishmanial antigens as well as to irrelevant antigens such as Toxoplasma gondii (Tg). Patients presenting with larger lesions had the highest lymphocyte proliferation indexes. A high frequency of Tg-specific cells was detected in the lesions by limiting dilution assay, similar to the frequency of Leishmania-specific cells. Importantly, Tg-reactive cells were not found in lesions of patients without a history of toxoplasmosis. The proportion of Leishmania-reactive CD4(+) and CD8(+) T cells in the lesions was quite variable. Overall, these data suggest that T cells reactive to nonrelevant antigens can migrate to leishmanial lesions and possibly influence the pathogenesis of the disease.

T helper cytokine patterns: defined subsets, random expression, and external modulation

Although T cell effector subsets, defined by cytokine patterns, have been recognized for more than 20 years, the functional cytokine expression patterns in vivo are still in considerable doubt, particularly for human T cells. At least three new subsets have been recently identified, but the committed cytokine pattern of a T cell (e.g., Th1 cells produce IL-2, interferon-gamma, and lymphotoxin) may differ from the expression pattern of one cell on one occasion, which may be a subset of its full potential. Recent advances in flow cytometry allowed detailed cytokine patterns of antigen-stimulated cells to be identified directly ex vivo. These patterns are clearly more diverse than the major subsets identified as committed phenotypes. Additional contributions to diversity may include new committed subsets, random expression of only part of the committed pattern, and modification of the expression patterns by cytokines and other mediators.

IL-2 absorption affects IFN-γ and IL-5, but not IL-4 producing memory T cells in double color cytokine ELISPOT assays

Cytokine assays are gaining increasing importance for human immune monitoring because they reliably detect antigen-specific T cells in primary PBMC, even at low clonal sizes. Double color ELISPOT assays permit the simultaneous visualization of cells producing two different cytokines. Permitting the simultaneous assessment of type 1 and 2 immunity and due to the limited numbers of PBMC available from human study subjects, double color assays should be particularly attractive for clinical trials. Since the performance of double color assays has not yet been validated, we set out to compare them to single color measurements. Testing the recall antigen-induced cytokine response of PBMC, we found that double color assays regularly provided lower numbers of IFN-gamma and IL-5 spots than single color measurements when IL-2 detection was part of the double color assay. We showed that the inhibitory effect resulted from IL-2 absorption and could be overcome by either antibody free preactivation cultures or by inclusion of anti-CD28 antibody. In contrast, the simultaneous detection of IL-2 did not affect the numbers of IL-4 spots. Therefore, unlike IL-2/IL-4 and IFN-gamma/IL-5 assays, IL-2/IFN-gamma, and IL-2/IL-5 assays require compensation for the IL-2 capture to provide accurate numbers for the frequencies of cytokine producing memory T cells.

Differential effects of IFN-alpha on the expression of various TH2 cytokines in human CD4+ T cells

BACKGROUND

In both human subjects and mice, T helper cells are classified into 2 subsets, TH1 and TH2 cells, on the basis of the cytokines they produce. Although IFN-alpha has been shown to enhance human TH1 responses, its influences on human TH2 responses have not yet been fully characterized. In addition, the mechanism for induction of TH1 responses by IFN-alpha has not been fully delineated.

OBJECTIVE

The present study was undertaken to explore the direct effects of IFN-alpha on the expression of various cytokines in human CD4+ T cells with a system using immobilized anti-CD3, which permits activation of CD4+ T cells in the complete absence of accessory cells.

METHODS

Highly purified CD4+ T cells obtained from healthy donors were stimulated with immobilized anti-CD3 with or without IFN-alpha and IL-12 in the complete absence of accessory cells. The production of cytokines was estimated by means of ELISA. The expression of mRNA for various cytokines, as well as transcription factors, was evaluated by using quantitative PCR.

RESULTS

IFN-alpha enhanced IL-4 protein and mRNA expression in immobilized anti-CD3-stimulated CD4+ T cells, irrespective of the presence of IL-12, whereas IFN-alpha suppressed the expression of IL-5 and IL-13. Of note, IFN-alpha enhanced the expression of mRNA for c-Maf, T-bet, and Fox-P3, irrespective of the presence of IL-12, but not that for GATA-3, in anti-CD3-stimulated CD4+ T cells.

CONCLUSION

These results indicate that IFN-alpha enhances the induction of TH1 responses through upregulation of T-bet mRNA expression, as well as the induction of TH2 responses through upregulation of c-Maf mRNA expression, followed by IL-4 expression. Moreover, the data also suggest that IFN-alpha might suppress the expression of IL-5 and IL-13 in differentiated TH2 cells.

Mucosal T-cell phenotypes in persistent atopic and nonatopic rhinitis show an association with mast cells

BACKGROUND

Allergic rhinitis is characterized by selective expansion of T cell subsets with a CD4+ phenotype. Recently, we identified a subpopulation of nonallergic rhinitis subjects with increased epithelial mast cell and eosinophil populations, suggestive of local mucosal allergy. Previously, T cell subsets have not been characterized in this subselection of nonallergic subjects and furthermore, their relationship to mast cell and basophil effector cells remain unidentified.

OBJECTIVE

To determine if a subpopulation of nonallergic subjects with idiopathic rhinitis (IR) have localized allergy confined to their nasal mucosa by comparing the T cell subsets and major histocompatibility complex (MHC) II expressing cells to persistent allergic rhinitis (PAR). Furthermore, the relationship between T cell subsets and mast cells/basophils was investigated.

METHODS

None of the symptomatic patients in this study were clinically allergen-challenged. Nasal turbinate mucosa was removed from patients with PAR, IR and normal controls. Morphometry was performed on immunostained sections for T cell subset populations including CD3+, CD4+, CD8+, CD25+, CD45RA+, CD45RO+, human leucocyte antigen (HLA)-DRalpha (MHC class II), mast cell tryptase and for basophils.

RESULTS

Subjects with persistent allergic rhinitis differed to normal controls in showing significantly increased numbers of total (CD3+), activated (CD25+) and allergen-naïve (CD45RA+) T lymphocytes in their nasal mucosa (P < 0.025). The naïve CD45RA+ memory T cells correlated to mucosal mast cells in PAR (P = 0.03). IR patients differ to allergic subjects in showing significantly reduced numbers of epithelial HLA-DRalpha+ cells (P = 0.007), but increased numbers of CD8+ lymphocytes (P = 0.02). The CD8+ T cells correlated with mucosal mast cell numbers (P = 0.02). In both rhinitis groups, basophils were present in very low numbers obviating the need for statistical analysis.

CONCLUSION

PAR is characterized by increased numbers of CD3+, CD25+ and CD45RA+ T lymphocytes compared with normal mucosa. Allergic and nonallergic rhinitis groups can be separated by significant differences in the number of epithelial antigen presenting cells (APCs) (HLA-DRalpha+) and sub-epithelial activated (CD25+) T cells. Moreover, IR patients do not significantly differ to their allergic counterparts with respect to total (CD3+) and naïve (CD45RA+) T cell numbers, or numbers of epithelial activated (CD25+) lymphocytes. IR subjects show significantly increased numbers of CD8+ lymphocytes compared with control mucosa and although our findings suggest that the initiating inflammatory events may differ, both rhinitis groups show a similarity in pathology involving mucosal mast cells with an association to infiltrating T cells.

Hybrid Cell Vaccination in Metastatic Melanoma

Hybrid cell vaccination with cell fusion products (CFPs) of autologous tumor cells and mature allogenic MHC II bearing dendritic cells has been described to induce cytotoxic T lymphocyte (CTL)-mediated immune responses. The aim of this study was to assess safety, antitumor activity, and immune responses of a CFP-vaccine in patients with disseminated malignant melanoma. In a phase I/II study, we treated 11 patients by monthly intracutaneous or subcutaneous application of a CFP vaccine generated by electrofusion of autologous melanoma cells with mature allogenic dendritic cells. In addition, patients received subcutaneous low-dose interleukin-2 injections for 6 days after each vaccination. No serious adverse effects were observed. Ten patients showed progressive disease and one patient had a short-lasting stable disease. None of the patients developed a positive delayed-type hypersensitivity reaction against irradiated autologous melanoma cells. In 2 patients, who were monitored in more detail, we found no evidence of induction of a specific antimelanoma T-cell response by analyzing the proliferation, cytokine secretion, and cytotoxicity of their T cells toward autologous melanoma cells. No unequivocal beneficial effects of the used CFP vaccine could be demonstrated.

CD4+ and CD8+ cells in cryopreserved human PBMC maintain full functionality in cytokine ELISPOT assays

The frequency and the cytokine signature of antigen-specific T cells in the blood reflect the magnitude and the quality of T cell immunity in vivo. Recently, cytokine enzyme-linked immunospot (ELISPOT) assays performed on freshly isolated peripheral blood mononuclear cells (PBMC) emerged as a promising tool for monitoring these key parameters, providing direct feedback information on the efficacy of vaccinations and immune therapies. However, performing ELISPOT assays with freshly isolated cells is not readily feasible in the context of clinical trials. The ability to obtain valid ELISPOT data on cryopreserved samples would greatly enhance ex vivo immune monitoring capabilities. We have therefore systematically studied antigen-specific T cell responses in freshly isolated PBMC and after cryopreservation. Four healthy donors were selected that displayed T cell responses to six recall antigens. The antigen reactive T cells were defined as CD4 or CD8 cells, and their cytokine effector class was established measuring interferon (IFN)-gamma, interleukin (IL)-2, IL-4 and IL-5. The donors were bled at three different time points, and their PBMC were tested fresh and after freeze-thawing. The results showed that the frequencies and type 1/type 2 cytokine signatures of recall antigen-specific CD4 and CD8 cells are unaffected after cryopreservation. In contrast to these data obtained on human PBMC, cryopreservation of murine spleen cells causes a decrease in cytokine secretion.

Antigen-specific T cell response in infants after recombinant hepatitis B virus vaccination at birth: evaluation of T helper lymphocyte diversity

Recombinant hepatitis B virus antigen (rHBsAg)-specific CD4+ T cell clones (TCC) were isolated and expanded from the peripheral blood of nine children vaccinated at birth against the hepatitis B (HB) virus. Four of them responded with protective antibody production (responders), three subjects were unable to produce detectable antibody levels even after revaccination (nonresponders), and two infants produced antibodies only after revaccination (slow responders). TCC were then characterized for their ability to produce cytokines known to be important for T cell expansion (interleukin-2, IL-2) and/or effector functions (IL-4, IFN-gamma, IL-10). Results demonstrated that the frequency of rHBsAg-specific TCC in the samples of nonresponders was comparable to or higher than that in the samples of responders. Nevertheless, the majority of TCC obtained from responders or from slow responders before revaccination displayed the T helper 1 (T(H1))-dominant phenotype, while the majority of TCC obtained from nonresponders were nonpolarized T lymphocytes. After revaccination, the distribution of the different T(H) subsets in slow responders was heterogeneous. Overall, our present data suggest that an absence or delay in developing an rHBsAg-specific antibody response to vaccination is not associated with the capacity to generate an Ag-specific T cell response. However, compared to responders, nonresponding infants react to the rHBsAg vaccination with a reduced capacity to expand and differentiate toward polarized T(H) cells.

Lipocalin allergen Bos d 2 is a weak immunogen

The immunological characteristics of an important group of animal-derived allergens, lipocalins, are poorly known. To explore the immunology of the lipocalin allergen Bos d 2, several mouse strains with different H-2 haplotypes were immunized with the allergen. Only the BALB/c mouse mounted a distinct humoral response against Bos d 2. The proliferative spleen cell responses of all mouse strains remained very weak. Further experiments with BALB/c mice confirmed that Bos d 2 is a weak inducer of both humoral and cellular responses, and that the responses were weaker than with the control antigens hen egg lysozyme (HEL) and tetanus toxoid. IgG subclass analyses showed that Bos d 2 was prone to favor the T(h)2 response. Although s.c. immunization using complete Freund's adjuvant favored the T(h)1-deviated immune response by lymph node cells, Bos d 2 was able to induce the production of IL-4 while the control antigen HEL did not. Epitope mapping revealed that BALB/c mice recognized one immunodominant epitope in Bos d 2, almost identical to that recognized by humans. The epitope was shown to be immunogenic in subsequent experiments. However, further studies are needed to clarify the significance of priming and stimulation doses of the immunodominant and other epitopes in Bos d 2 for the outcome of immune response against the allergen. The murine immune response against Bos d 2 closely resembled that observed in humans. The weak immunogenicity of Bos d 2 may be associated with its allergenicity.

GATA-3 has dual regulatory functions in human interleukin-5 transcription

Interleukin-5 (IL-5) is a T-cell cytokine involved in Type 2 diseases and is commonly described as being coordinately regulated with other Type 2 cytokines, such as IL-4 and IL-13. Considering the unique control of eosinophilia by IL-5, such coordinate regulation would be surprising. In fact, the biological specificity of eosinophilia and its control by IL-5 suggests a unique and independent control of IL-5 regulation. In this report we show the binding of GATA-3 to three sites in the human IL-5 promoter in the human T-cell line PER117. The previously identified -70 site and another site at position -152 are shown to positively regulate IL-5 transcription. More importantly, the site located at -400 acts as a powerful repressor of IL-5 transcription with mutagenesis of this site allowing a high level expression of IL-5 without the activation of other factors normally required for IL-5 expression. Whereas GATA-3 has been proposed to be involved in the regulation of the IL-4/IL-5/IL-13 locus, we show here that it has another function in controlling IL-5 transcription that supports the observed unique biological function of this cytokine.

The role of IFN-gamma in the production of Th2 subpopulations: implications for variable Th2-mediated pathologies in autoimmunity

It has become increasingly apparent in studies of mutant mice and observations of disease that cytokine production by fully committed effector T cells within the Th1 and Th2 phenotype can vary within each group. This can potentially influence the type and effectiveness of a given immune response. The factors responsible for inducing variable Th1 and Th2 subtype responses have not been well established. Using transgenic mice expressing the myelin basic protein-specific TCR, we demonstrate here that two distinct populations of Th2 cells that are characterized primarily by differential IL-4 and IL-5 expression levels can be generated depending upon the levels of IFN-gamma present at the time of priming. We also demonstrate that populations expressing high levels of IL-4 relative to IL-5 vs those with intermediate levels of IL-4 relative to IL-5 are stable and possess distinct effector functions in an experimental autoimmune encephalomyelitis model.

Dexamethasone inhibits the binding of nuclear factors to the IL-5 promoter in human CD4 T cells

BACKGROUND

IL-5 is produced by the T(H)2 subset of CD4(+) T lymphocytes and is necessary for the eosinophilia typical of allergic conditions. Glucocorticoids such as dexamethasone are highly effective inhibitors of eosinophilic inflammation, and one of their effects is inhibition of IL-5 gene expression.

OBJECTIVE

We wished to examine the effect of dexamethasone on the binding of nuclear factors from primary human CD4(+) T lymphocytes to the RE-I and RE-II positively acting regulatory elements of the IL-5 promoter.

METHODS

CD4(+) T cells, purified from PBMCs by magnetic bead separation, were activated with anti-CD3 antibody and phorbol myristate acetate. Nuclear extracts were tested in electrophoretic mobility shift assays with probes based on RE-I and RE-II.

RESULTS

In extracts from activated cells, the RE-II region of the promoter formed a complex that was shown by supershift assay to contain NFATc. This complex was abolished by treatment of the cells with dexamethasone before activation and was weak or absent in unactivated cells. By contrast, binding to the RE-I region and to the GATA-3 site within RE-I was observed in resting cells and was not affected by activation or treatment with dexamethasone.

CONCLUSION

Dexamethasone inhibits the inducible binding of factors to the RE-II region but does not affect the constitutive binding to the RE-I region. Characterization of such molecular effects of glucocorticoids could enable the development of specific inhibitors of IL-5 expression that lack the side effects of glucocorticoids.

Reduction of serum interleukin-5 levels reflect clinical improvement in patients with atopic dermatitis

Cytokines, in particular IL-4 and IL-5, regulate IgE synthesis and eosinophil activation in atopic dermatitis (AD). To elucidate whether the serum levels of IL-4 and IL-5 are related to the serum IgE level, eosinophilia, or clinical severity of the disease, 25 cases with AD were studied. Blood samples were isolated from two groups of donors: 1) patients with AD (n = 25); 2) non-allergic individuals (NA, n = 20) with serum IgE levels below 100 IU/ml and with blood eosinophil counts below 250/microliter. Each parameter was evaluated at least twice in AD patients at the beginning of the study and after 4, 8 or 12 weeks of treatment. IL-4 was hardly detected in AD and NA, but IL-5 was increased (> 10 pg/ml) in most cases (22/25) of AD group with 513.6 pg/ml as the mean. AD with normal serum IgE levels exhibited increased levels of IL-5, whereas AD with high serum IgE levels did not necessarily have elevated IL-5 levels. The IL-5 level tended to change in parallel with the clinical severity in each AD case, although the level itself was not correlated with the clinical severity per se. A significant decrease of IL-5 was observed in AD when the clinical severity decreased. Eosinophils also decreased along with the improvement of AD, whereas the serum level of IgE did not change during the observation period. Our results suggest that IL-5 is involved in the regulation of clinical courses of AD and that its kinetics at the serum level reflects the clinical activity of AD.

Cytokine profile in minor salivary glands from patients with bronchial asthma

BACKGROUND

T lymphocytes are important components of the bronchial inflammatory cell infiltrate in asthma. Because lymphocytes activated in the respiratory tract recirculate to remote glandular and mucosal sites, we previously studied the histologic features of minor salivary glands (MSGs) in bronchial asthma and found an airway-like inflammation with T-lymphocyte infiltration, the presence of mast cells that were often degranulated, and basement membrane thickening but no eosinophil infiltration.

OBJECTIVE

We sought to investigate the cellular infiltration and cytokine profile in MSGs from untreated asthmatic subjects, steroid-treated asthmatic subjects, and control subjects and to compare these values with those found in bronchial biopsy specimens.

METHODS

The cellular infiltration was studied by using immunohistochemistry. Cytokine messenger (m)RNA expression for IL-4, IL-5, and IFN-gamma was determined by using in situ hybridization and cytokine immunoreactivity with immunohistochemistry.

RESULTS

A significant increase in CD4 and IL-4 mRNA(+) cells was observed in MSGs from asthmatic patients (both untreated and steroid-treated subjects) when compared with control subjects, which correlated with the clinical severity of asthma (FEV(1) and Aas score). In contrast to the bronchi, no IL-5 mRNA expression was observed in MSGs, and no difference was observed for MSG IFN-gamma mRNA between the groups. At the level of MSG protein expression, the 3 cytokines were seen, with a significant increase in IL-4 protein expression in steroid-treated asthmatic subjects compared with untreated asthmatic subjects and control subjects, but there were no differences between the groups in IL-5 and IFN-gamma protein expression.

CONCLUSION

The cytokine mRNA expression pattern observed in the MSGs of asthmatic subjects was different from that found in the bronchi, suggesting a different local immune regulation.

Dissociation of interleukin-4 and interleukin-5 production following treatment for Schistosoma haematobium infection in humans

Infection with Schistosoma haematobium, the causative agent of urinary schistosomiasis is characterized by high levels of specific immunoglobulin (Ig) E and eosinophilia. The primary cytokines driving production of IgE and eosinophilia are IL-4 and IL-5, respectively. In this study, IL-4 and IL-5 production in children from a schistosome endemic area of Zimbabwe were investigated. Blood samples were taken, stimulated in vitro with either mitogen or schistosome antigens and assayed for IL-4 and IL-5 production. These samples produced either IL-4 or IL-5 but rarely both cytokines when blood was cultured in vitro for 24 or 48 h. After 72 h culture in vitro, both cytokines were detected in most samples. These data imply that while IL-4 and IL-5 are both produced by schistosome infected people, they are not necessarily coproduced.

Revisiting tolerance induced by autoantigen in incomplete Freund's adjuvant

Injection of autoantigens in IFA has been one of the most effective ways of preventing experimental, T cell-mediated, autoimmune disease in mice. The mechanism that underlies this protection has, however, remained controversial, with clonal deletion, induction of suppressor cells or of type 2 immunity being implicated at one time or another. Using high resolution enzyme-linked immunospot (ELISPOT) analysis, we have revisited this paradigm. As models of autoimmunity against sequestered and readily accessible autoantigens, we studied experimental allergic encephalomyelitis, induced by myelin oligodendrocyte glycoprotein, proteolipid protein, myelin basic protein, and renal tubular Ag-induced interstitial nephritis. We showed that the injection of each of these Ags in IFA was immunogenic and CD4 memory cells producing IL-2, IL-4, and IL-5, but essentially no IFN-gamma. IgG1, but not IgG2a, autoantibodies were produced. The engaged T cells were not classic Th2 cells in that IL-4 and IL-5 were produced by different cells. The IFA-induced violation of self tolerance, including the deposition of specific autoantibodies in the respective target organs, occurred in the absence of detectable pathology. Exhaustion of the pool of naive precursor cells was shown to be one mechanism of the IFA-induced tolerance. In addition, while the IFA-primed T cells acted as suppressor cells, in that they adoptively transferred disease protection, they did not interfere with the emergence of a type 1 T cell response in the adoptive host. Both active and passive tolerance mechanisms, therefore, contribute to autoantigen:IFA-induced protection from autoimmune disease.

Detection of intracytoplasmic cytokines by flow cytometry

Flow cytometry has been used as a powerful technique for studying cell surface antigen expression as well as intracellular molecules. Its capability of analyzing multiple parameters simultaneously on a single cell has allowed identification and studies of functional cell subsets within heterogeneous populations. In this respect, several techniques have been developed during the past few years to study cytokine-producing cells by flow cytometry in humans and several animal models.

Tumor-specific CD4+ T lymphocytes from cancer patients are required for optimal induction of cytotoxic T cells against the autologous tumor

This study focuses on the specific CD4+ T cell requirement for optimal induction of cytotoxicity against MHC class II negative autologous tumors (AuTu) collected from patients with various types of cancer at advanced stages. CD4+ T cells were induced in cultures of cancer patients' malignant effusion-associated mononuclear cells with irradiated AuTu (mixed lymphocyte tumor cultures (MLTC)) in the presence of recombinant IL-2 and recombinant IL-7. Tumor-specific CD4+ T cells did not directly recognize the AuTu cells, but there was an MHC class II-restricted cross-priming by autologous dendritic cells (DCs), used as APC. CD8+ CTL, also induced during the MLTC, lysed specifically AuTu cells or DCs pulsed with AuTu peptide extracts (acid wash extracts (AWE)) in an MHC class I-restricted manner. Removal of CD4+ T cells or DCs from the MLTC drastically reduced the CD8+ CTL-mediated cytotoxic response against the AuTu. AWE-pulsed DCs preincubated with autologous CD4+ T cells were able, in the absence of CD4+ T cells, to stimulate CD8+ T cells to lyse autologous tumor targets. Such activated CD8+ T cells produced IL-2, IFN-gamma, TNF-alpha, and GM-CSF. The process of the activation of AWE-pulsed DCs by CD4+ T cells could be inhibited with anti-CD40 ligand mAb. Moreover, the role of CD4+ T cells in activating AWE-pulsed DCs was undertaken by anti-CD40 mAb. Our data demonstrate for the first time in patients with metastatic cancer the essential role of CD4+ Th cell-activated DCs for optimal CD8+ T cell-mediated killing of autologous tumors and provide the basis for the design of novel protocols in cellular adoptive immunotherapy of cancer, utilizing synthetic peptides capable of inducing T cell help in vivo.

Direct visualization of cytokine-producing recall antigen-specific CD4 memory T cells in healthy individuals and HIV patients

We have used computer-assisted cytokine ELISA spot analysis to measure the frequencies, the type of cytokine, and the amount of cytokine produced by individual recall Ag-specific CD4 memory cells in freshly isolated blood. We studied the memory cells specific for tetanus toxoid and purified protein derivative in 18 healthy individuals and in 22 HIV-infected patients on highly active antiretroviral therapy (HAART). In healthy individuals, the frequency, cytokine signature, and cytokine production per cell of these memory cells were stable over time. Although it is presently unclear whether the maintenance of the memory T cell pool depends upon Ag persistence, cross-reactive Ag stimulation, or cytokine-driven bystander stimulations and expansions, our data strongly argue for a stable memory cell pool in healthy individuals. In HIV patients, however, the frequency of these memory cells was a function of the viral load. The decreased numbers of functional memory cells in patients with high viral loads might provide one mechanism behind the immunodeficient state. Although the cytokine output per cell was unaffected in most patients (20 of 24), in some patients (4 of 24) it was >100-fold reduced, which might provide an additional mechanism to account for the reduced immunocompetence of these patients. The ability to visualize directly and quantify the cytokine produced by the low frequency memory cells in freshly isolated blood that have been physiologically stimulated by Ag should aid comprehensive studies of the Ag-specific memory cell pool in vivo, in health and disease.

Single-cytokine-producing CD4 memory cells predominate in type 1 and type 2 immunity

The patterns of Ag-induced cytokine coexpression in normal, in vivo-primed CD4 memory T cells has remained controversial because the low frequency at which these cells occur has effectively prevented direct ex vivo measurements. We have overcome this limitation by using two-color cytokine enzyme-linked immunospot assays and computer-assisted image analysis. We found CD4 memory cells that simultaneously expressed IL-2, IL-3, IL-4, IL-5, and IFN-gamma to be rare (0-10%). This cytokine segregation was seen in adjuvant-induced type 1, type 2, and mixed immunity to OVA, in Leishmania infection regardless of the Ag dose used or how long after immunization the assay was performed. The data suggest that type 1 and type 2 immunity in vivo is not mediated by classic Th1 or Th2 cells but by single-cytokine-producing memory cells.

A study of cytokine protein secretion, frequencies of cytokine expressing cells and IFN-G gene polymorphisms in normal individuals

BACKGROUND

Cytokines are major regulators of immune responses, and there is evidence that they play a role in allograft rejection. Before embarking on a detailed study of pretransplant cytokine profiles in renal allograft recipients, we wished to investigate variations in cytokine protein secretion, numbers of cytokine expressing T cells, and cytokine gene polymorphisms in normal volunteers.

METHODS

Twenty normal healthy volunteers were studied. Cytokine protein secretion [interleukin- (IL) 2, IL-4, IL-10, and interferon- (IFN) y] and numbers of cytokine expressing CD3+ T cells (IL-2, IL-4, IL-10, and IFN-gamma) were quantified by means of enzyme-linked immunosorbent assay and two-color flow cytometry respectively. IFN-gamma gene polymorphisms were determined by polymerase chain reaction and autoradio graphy.

RESULTS

Large interindividual variations in both the quantity of IL-2, IL-4, IL-10, and IFN-gamma cytokine protein secreted and numbers of IL-2 and IFN-gamma expressing T cells were demonstrated. However, numbers of IL-4 and IL-10 expressing cells were found to be below detectable limits by flow cytometry. In the case of IFN-gamma, a bi-modal distribution was seen for the quantity of protein secreted. In addition, correlations were observed between IL-2 protein and frequency of IL-2 expressing T cells. However, no relationship was found between IFN-gamma protein levels, numbers of IFN-gamma expressing cells and IFN-gamma gene polymorphisms.

CONCLUSIONS

We have demonstrated large differences in both numbers of T helper 1 cytokine expressing cells and the quantity of T helper 1 and T helper 2 cytokine protein secreted between normal individuals. Although the amount of IL-2 protein secreted appeared to be determined by the frequency of IL-2 expressing cells, this was not the case for IFN-gamma.

Control of Leishmania infantum infection is associated with CD8(+) and gamma interferon- and interleukin-5-producing CD4(+) antigen-specific T cells

Visceral leishmaniasis is a severe and lethal disease caused by the protozoan parasites of the genus Leishmania. In areas where leishmaniasis is endemic, most infected individuals control the infection and remain asymptomatic; chemotherapy of visceral leishmaniasis restores some immunity which protects against relapses. In the present study, Leishmania-specific T-cell clones were established from six asymptomatic and five cured patients. Cytokines production by these clones was analyzed. A large fraction of the parasite-specific T-cell clones from asymptomatic patients were CD8(+) and produced high amounts of gamma interferon (IFN-gamma). Most CD4(+) T-cell clones from two asymptomatic subjects exhibited an unusual phenotype: production of high levels of IFN-gamma low levels of interleukin-4, (IL-4), but high levels of IL-5. In contrast, only few parasite-specific CD8(+) T-cell clones were obtained from cured patients after chemotherapy; moreover, CD4(+) T-cell clones from these patients exhibited an heterogeneous profile of cytokines from Th1-like to Th2-like phenotypes. These results point to CD8(+) T cells and to IL-5- and IFN-gamma-producing CD4(+) T cells as possible contributors to human resistance to Leishmania infection. They should stimulate new immunological approaches in the control of this disease.

The kinetics and stimulant dependence of cytokine production by blood and bronchoalveolar lavage T cells evaluated at the single cell level

We have previously shown that bronchoalveolar lavage (BAL) T cells from human airways predominantly produce interferon gamma (IFN-gamma) and interleukin 2 (IL-2) when stimulated ex vivo. The kinetics of TH1 and TH2 cell cytokine production by T cells from both blood and BAL were studied to establish the optimal time after stimulation either with pharbol myristate (PMA) and ionomycin or with the more physiological stimulus of anti-CD3 for intracellular cytokine detection of IFN-gamma, IL-2, IL-4 and IL-5 in both blood and BAL T cells. The optimal time for positive identification of IL-2 in both blood and BAL was 5 h after PMA/ionomycin stimulation, whereas the first peak for IFN-gamma was found after 5 h in blood but after only 3 h in BAL. T cells from different biological compartments responded differently to each of the stimuli. Whilst anti-CD3 stimulation did not induce TH1 cytokine production in blood T cells, it readily induced both IFN-gamma and IL-2 production in BAL T cells. The kinetics of cytokine production were found to be stimulus dependent. Whilst IL-2 production showed similar kinetics with both stimuli, the kinetics of IFN-gamma production differed between stimuli. We have also examined the effect of five different stimuli on cytokine production by T cells to determine whether different forms of stimulation may selectively stimulate or inhibit different cytokines. Not surprisingly, PMA/ionomycin induced a greater percentage of BAL T cells to produce TH1 cytokines. However, other than modest amounts of the TH2 cytokines IL-4 and IL-5 were not induced by any of the five stimuli.

Intracellular analysis of interleukin-2 induction provides direct evidence at the single cell level of differential coactivation requirements for CD45RA+ and CD45RO+ T cell subsets

Through measurements of intracellular cytokine production, evidence is provided at the single cell level that triggering different cell surface molecules preferentially activates discrete human peripheral blood (PB) T cell subsets. T cell costimulation due to cross-linking a variety of individual molecules (beta1, beta2, and beta7 integrins, CD26, CD43, or CD44), in conjunction with the CD3/TCR complex, preferentially activated CD45RO+ PB T lymphocytes. CD28, however, costimulated interleukin-2 (IL-2) production in both CD45RO+ and CD45RA+ subpopulations. The amount of soluble IL-2 produced by CD28 coactivation was 15-30-fold higher than that due to integrin or CD26-dependent coactivation, although even the lowest amount of soluble IL-2 produced was in the range of the high-affinity IL-2 receptor. The overall proliferative responses were similar among all costimulatory settings. This was in part due to the uniform upregulation of IL-2 receptor-alpha (IL-2R alpha) (CD25) expression on the entire T cell population activated under each of the different costimulatory conditions. The data provide direct evidence on a single cell level that activation of human CD45RA+ (naive) T cells is stringently controlled and, in these studies, limited to CD28 costimulation for induction of IL-2 production. In contrast, coactivation of CD45RO+ (memory) T lymphocytes can proceed by a variety of different PB T cell surface molecules.

Kinetics of intracytoplasmic Th1 and Th2 cytokine production assessed by flow cytometry following in vitro activation of peripheral blood mononuclear cells

BACKGROUND

Standard cytokine detection methods are unable to determine which cells are the producing cells. We report on the extent and under which conditions the multilabeling capability of flow cytometry (FCM) can bring new advances into the field.

METHODS

Five different cytokines, interleukin-2 (IL-2), -4, -5, -10 and interferon-gamma (IFN-gamma), were assessed simultaneously under five ex vivo stimulation conditions in peripheral blood mononuclear cells from five healthy volunteers in a 5-day kinetic study. A second group of 35 volunteers was assessed for IFN-gamma and IL-2 production.

RESULTS

This study showed that (a) intracytoplasmic cytokines were almost undetectable within unstimulated cells, (b) intracytoplasmic cytokines were detected only in CD69(+) T lymphocytes, and (c) intracytoplasmic IL-2 and IFN-gamma were dramatically upregulated after stimulation with phorbol myristate acetate (PMA)-ionomycin in a biphasic response or with PMA-phytohemagglutinin (one major peak only at 18 h) but to a lesser extent with other stimuli such as monoclonal antibodies. Th2 cytokines were detected at a later time point and at lower levels. PMA/ionomycin stimulation after 4 h and 18 h of culture in 35 other volunteers individualized several subgroups according to the frequency of IFN-gamma- or IL-2-producing cells--IFN-gamma delayed producers (n = 10/35), IFN-gamma low producers (n = 8/35), and IL-2 delayed producers (n = 16/35)--as opposed to IFN-gamma or IL-2 normal producers.

CONCLUSIONS

FCM appears to be a good tool to examine cell cytokine status in pathology (allergy, autoimmune disease, etc.) provided that optimal stimulation conditions and multiple time-point cultures are used. It also seems to be a relevant method to define new Th subsets further.

Enhancement of human IL-4 activity by soluble IL-4 receptors in vitro

The recombinant form of the extracellular domain of the IL-4 receptor (sIL-4R) is a potential candidate to neutralize IL-4; however, murine sIL-4R displayed both antagonistic and agonistic activity in vivo. Here we show that human recombinant sIL-4R induced the formation of complexed IL-4 in supernatants of activated T cells in a dose-dependent manner as measured by newly developed enzyme-linked immunosorbent assays. These IL-4/sIL-4R complexes liberated free IL-4 even after prolonged culturing. In contrast, in the absence of exogenously added sIL-4R, free IL-4 was rapidly consumed or proteolytically degraded in cultures of activated T cells. Thus, no IL-4 bioactivity could be determined in supernatants of T cells activated in the presence of IL-4 for 6 days. In contrast, the same cultures carried out in the presence of sIL-4R showed marked IL-4 bioactivity. While low concentrations of sIL-4R enhanced IL-4-driven inhibiton of IFN-gamma production by activated T cells, higher concentrations neutralized IL-4. Together, human sIL-4R, besides its activity as an antagonist to IL-4, also possesses protective and agonistic functions for IL-4, which may be relevant for clinical studies aiming to neutralize IL-4 in vivo.

IFN-gamma is only partially restored by co-stimulation with IL-12, IL-2, IL-15, IL-18 or engagement of CD28

BACKGROUND

Although it is well established that T cells derived from patients with atopic diseases produce low levels of interferon-gamma (IFN-gamma), the mechanisms responsible for this phenomenon are poorly understood.

OBJECTIVES

To elucidate whether IFN-gamma production may be restored by co-stimulatory molecules known to increase IFN-gamma production in vitro. Further, to investigate whether deficient IFN-gamma production is associated with disease activity.

METHODS

Purified peripheral T cells obtained from patients with severe atopic dermatitis (AD), individuals with a history but no symptoms of AD and healthy control subjects were activated with anti-CD3 MoAbs in the presence or absence of anti-CD28 MoAbs, interleukin (IL-) 12, IL-2, IL-15 or IL-18. IFN-gamma production was determined at the single cell level by flow cytometry, as well as by ELISA.

RESULTS

Activated T cells from patients with severe AD produced less IFN-gamma than T cells from healthy control individuals. IL-12 or engagement of CD28 enhanced IFN-gamma production in both healthy and atopic T cells. However, absolute values of IFN-gamma were still different. IL-2, IL-15 and IL-18 did not restore IFN-gamma production. T cells from individuals with a history of AD produced more IFN-gamma than those from subjects with severe AD, but less than T cells from healthy individuals. Atopic T cells expressed regular levels of CD3, CD28 and Stat4, the main signal transducer and activator of transcription for IL-12. IL-4, IL-10 and TGF-beta production by T cells were not different between healthy and atopic individuals.

CONCLUSION

IFN-gamma deficiency in atopic T cells is not due to a lack of responsiveness to CD28, IL-12, IL-2, IL-15 or IL-18. T cell-derived cytokines able to antagonize IFN-gamma do not contribute to decreased IFN-gamma production. The extent of IFN-gamma deficiency seems to be dependent on disease activity.

Common features of T cell reactivity in persistent helminth infections: lymphatic filariasis and schistosomiasis

This review highlights striking similarities in the down-regulated inflammatory responses that are observed in chronic infectious diseases. It is clear that peripheral mononuclear cells show poor antigen-specific T cell proliferation in lymphatic filariasis as well as schistosomiasis. With respect to cytokines both Th1- and Th2-type products are down-regulated during chronic infection. Drug treatment restores responsiveness in both diseases indicating a link between infection and immune suppression. Interestingly, immunological responses in subjects carrying recent infections are characterized by strong proliferation to parasite antigen and IFN-gamma production. These heightened responses are gradually down-regulated with increased length of exposure to infection.

Characterisation of inducible DNase I hypersensitive sites flanking the human interleukin-5 gene

Interleukin-5 (IL-5) production is necessary for eosinophilia associated with allergic conditions and parasitic infection. IL-5 mRNA is transiently expressed by activated T-lymphocytes. In this report, we have analysed DNA regulatory regions associated with inducible IL-5 expression in the human HSB-2 T-cell line. Only low levels of transcriptional activity were induced in cells transfected with up to 1.2 kb of DNA upstream of the IL-5 gene. DNase I hypersensitivity analysis was employed to identify additional regulatory sequences located outside this region. Two hypersensitivity sites (HS) were identified, one 2.5 kb 5' and the other 1.6 kb 3' from the gene, that were induced on activation of HSB-2 cells by stimuli that induced IL-5 expression. The 5' site, but not the 3' site, was found in primary human T-cells. The presence of the 5' HS did not always coincide with IL-5 expression. Inclusion of the region encompassing the 5' HS in promoter studies mediated a moderate increase in transcriptional activity, suggesting that enhancer elements essential for induction of maximal IL-5 transcription reside at a greater distance from the IL-5 gene.

Essential role of nuclear factor kappaB in the induction of eosinophilia in allergic airway inflammation

The molecular mechanisms that contribute to an eosinophil-rich airway inflammation in asthma are unclear. A predominantly T helper 2 (Th2)-type cell response has been documented in allergic asthma. Here we show that mice deficient in the p50 subunit of nuclear factor (NF)- kappaB are incapable of mounting eosinophilic airway inflammation compared with wild-type mice. This deficiency was not due to a block in T cell priming or proliferation in the p50(-/-) mice, nor was it due to a defect in the expression of the cell adhesion molecules VCAM-1 and ICAM-1 that are required for the extravasation of eosinophils into the airways. The major defects in the p50(-/-) mice were the lack of production of the Th2 cytokine interleukin 5 and the chemokine eotaxin, which are crucial for proliferation and for differentiation and recruitment, respectively, of eosinophils into the asthmatic airway. Additionally, the p50(-/-) mice were deficient in the production of the chemokines macrophage inflammatory protein (MIP)-1alpha and MIP-1beta that have been implicated in T cell recruitment to sites of inflammation. These results demonstrate a crucial role for NF-kappaB in vivo in the expression of important molecules that have been implicated in the pathogenesis of asthma.

Segregation of type 1 cytokine production in human peripheral blood lymphocytes: phenotypic differences between IFN-gamma and IL-2-producing cells in the CD8+ T cell subset

T cell clones are classified as type 0, 1 or 2 depending on the lymphokines they produce. However, it has remained unclear whether single cells of a given type produce one or several cytokine species. Flow cytometric analysis of peripheral blood lymphocytes (PBL) obtained from 20 healthy donors for the production of the type 1 cytokines IFN-gamma and IL-2 revealed very few cells that co-expressed both cytokines independently of the mitogenic stimulus used for PBL activation. Similarly, kinetic studies of cytokine synthesis indicated a low percentage of IFN-gamma/IL-2 double-positive T cells at all time points. Reverse transcription-PCR analysis of sorted IL-2- and IFN-gamma-positive T cells showed the presence of IL-2- or IFN-gamma-specific mRNA only in those cells expressing the corresponding cytokine. This segregation of the two type 1 cytokines was lost in long-term cultured T cells and in T cell clones. A high percentage of cells expressing only IL-2 or IFN-gamma was observed even when the production of these cytokines was evaluated on CD4- and CD8+ subsets. Moreover, in some healthy individuals, IFN-gamma and IL-2 production by CD8+ T cells was related to CD8+ expression levels and cell size, i. e. IL-2-expressing cells were generally smaller with more intense CD8+ staining as compared with IFN-gamma-producing T cells. These data indicate that activated T lymphocytes are strongly committed in vivo to produce IFN-gamma or IL-2 and emphasizes the independent regulation of the two cytokine genes.

Frequencies of T cells expressing interleukin-4 and interleukin-5 in atopic asthmatic children. Comparison with atopic asthmatic adults

T-cell-derived cytokines have been implicated in the pathogenesis of asthma and it has been suggested that Th2-type cytokines (interleukin-4 [IL-4], interleukin-5 [IL-5]) are pivotal in the allergic inflammation. However, there are little data on human cytokine production by individual T cells at the protein level, in particular in asthmatic children. In this study we analyzed the cytokine production at the single cell level in peripheral blood from mild atopic asthmatic (AA) children and adults and age-matched atopic nonasthmatic (AN) and nonatopic nonasthmatic (NN) control subjects (n = 9 in each group) using the technique of intracellular cytokine detection by flow cytometry. Comparing asthmatic children with atopic and nonatopic control subjects, an increased percentage of IL-5-producing T cells (AA: median 4.9% [range 1.1 to 8.9%]; AN: 0.3% [0.2 to 0.9%], p = 0.003; NN: 0.4% [0.1 to 3.8%], p = 0.001) was detectable, with a positive correlation to the number of peripheral eosinophils and to bronchial hyperresponsiveness. The frequency of IL-4-producing T cells was increased in both atopic groups compared with nonatopic controls (AA: 1.2% [0.2 to 2.6%], p = 0.011; AN: 0.8% [0.4 to 3.7%], p = 0.007; NN: 0.4% [0.2 to 0.9%]) with a positive correlation to total IgE concentration. In adults there were no differences in IL-5- or IL-4-producing T cells between all three groups. A substantial proportion of T cells coproducing IL-4 and IL-5 was not detectable in children and adults. These findings indicate that in asthmatic children the frequencies of Th2-type-producing T cells are increased and that expression of IL-4 and IL-5 is regulated independently.

IL-5 and IL-5 receptor in asthma

Eosinophils, along with mast cells are key cells involved in the innate immune response against parasitic infection whereas the adaptive immune response is largely dependent on lymphocytes. In chronic parasitic disease and in chronic allergic disease, IL-5 is predominantly a T cell derived cytokine which is particularly important for the terminal differentiation, activation and survival of committed eosinophil precursors. The human IL-5 gene is located on chromosome 5 in a gene cluster that contains the evolutionary related IL-4 family of cytokine genes. The human IL-5 receptor complex is a heterodimer consisting of a unique alpha subunit (predominantly expressed on eosinophils) and a beta subunit which is shared between the receptors for IL-3 & GM-CSF (more widely expressed). The alpha subunit is required for ligand-specific binding whereas association with the beta subunit results in increased binding affinity. The alternative splicing of the alpha IL-5R gene which contains 14 exons can yield several alpha-IL-5R isoforms including a membrane-anchored isoform (alpha IL-5Rm) and a soluble isoform (alpha IL-5Rs). Cytokines such as IL-5 produce specific and non-specific cellular responses through specific cell membrane receptor mediated activation of intracellular signal transduction pathways which, to a large part, regulate gene expression. The major intracellular signal transduction mechanism is activation of non-receptor associated tyrosine kinases including JAK and MAP kinases which can then transduce signals via a novel family of transcriptional factors named signal transducers and activators of transcription (STATS). JAK2, STAT1, and STAT5 appear to be particularly important in IL-5 mediated eosinophil responses. Asthma is characterized by episodic airways obstruction, increased bronchial responsiveness, and airway inflammation. Several studies have shown an association between the number of activated T cells and eosinophils in the airways and abnormalities in FEV1, airway reactivity and clinical severity in asthma. It has now been well documented that IL-5 is highly expressed in the bronchial mucosa of atopic and intrinsic asthmatics and that the increased IL-5 mRNA present in airway tissues is predominantly T cell derived. Immunocytochemical staining of bronchial biopsy sections has confirmed that IL-5 mRNA transcripts are translated into protein in asthmatic subjects. Furthermore, the number of activated CD4 + T cells and IL-5 mRNA positive cells are increased in asthmatic airways following antigen challenge and studies that have examined IL-5 expression in asthmatic subjects before and after steroids have shown significantly decreased expression following oral corticosteroid treatment in steroid-sensitive asthma but not in steroid resistant and chronic severe steroid dependent asthma. The link between T cell derived IL-5 and eosinophil activation in asthmatic airways is further strengthened by the demonstration that there is an increased number of alpha IL-5R mRNA positive cells in the bronchial biopsies of atopic and non-atopic asthmatic subjects and that the eosinophil is the predominant site of this increased alpha IL-5R mRNA expression. We have also shown that the subset of activated eosinophils that expressed mRNA for membrane bound alpha IL-5r inversely correlated with FEV1, whereas the subset of activated eosinophils that expressed mRNA for soluble alpha IL-5r directly correlated with FEV1. Hence, not only does this data suggest that the presence of eosinophils expressing alpha IL-5R mRNA contribute towards the pathogenesis of bronchial asthma, but also that the eosinophil phenotype with respect to alpha IL-5R isoform expression is of central importance. Finally, there are several animal, and more recently in vitro lung explant, models of allergen induced eosinophilia, late airway responses (LARS), and bronchial hyperresponsiveness (BHR)--all of which support a link between IL-5 and airway eosinophilia and bronc

Detection of and discrimination between total and free human interleukin-4 and free soluble interleukin-4 receptor by ELISA

Interleukin-4 (IL-4) signaling is initiated by binding of IL-4 to the high-affinity IL-4 receptor alpha-chain and subsequent interaction with the common gamma-chain. Soluble forms of the extracellular domain of the alpha-chain (sIL-4R) were shown to be present in biological fluids and, dependent on the concentration, enhance or inhibit IL-4 activity by forming IL-4/sIL-4R complexes. To discriminate between free and potentially active IL-4 from the inactive and complexed form, we have established a set of new ELISA systems for the measurement of human IL-4 in its distinct forms. To select suitable pairs of anti-IL-4 antibodies, a chequerboard interference analysis with six highly-selective human IL-4 specific monoclonal antibodies was performed. For the determination of total IL-4, a monoclonal capture antibody was used that binds IL-4 outside the binding site of the IL-4R alpha-chain. Another antibody recognizing an epitope of the alpha-chain binding site was chosen for the detection of free IL-4. The binding of this antibody was inhibited in a dose-dependent fashion by recombinant sIL-4R. Assays for both total and free IL-4 exhibited a sensitivity of 8 pg/ml and a dynamic range up to 1000 pg/ml. Human sIL-4R was detected by two monoclonal antibodies directed against different epitopes. This ELISA was inhibited by recombinant IL-4 suggesting the measurement of predominantly free sIL-4R. Complexes between soluble IL-4R and IL-4 were detected by a monoclonal anti-sIL-4R antibody in combination with an anti-IL-4 antibody. When supernatants of activated T cells were analyzed, the majority of the IL-4 was in free form. The amount of complexed IL-4 was low as indicated by the fact that most of total IL-4 could be detected as free IL-4. Although values obtained for complexed IL-4 correlated with the difference between total and free IL-4, precise values could not be determined, presumably due to the dynamic nature of the complex between the two proteins. We suggest that the ability to quantitate total and free IL-4 in combination with sIL-4R may provide a new insight of the role that IL-4 plays in different pathophysiological conditions.

Effects of anti-IgE in asthmatic subjects

A humanized murine monoclonal antibody directed to the Fc epsilon R1-binding domain of human IgE (rhuMAb-E25) has been shown to inhibit the binding of IgE to mast cells without provoking mast cell activation. To examine the effects of neutralizing IgE on allergic airway responses, we assessed the effects of 9 wk of treatment with rhuMAb-E25 in a parallel group, randomized, double-blind, placebo-controlled study of 19 allergic asthmatic subjects. We found that treatment with rhuMAb-E25 reduced the serum IgE, increased the dose of allergen needed to provoke an early asthmatic response, reduced the mean maximal fall in FEV1 during the early response (30 +/- 10% at baseline to 18.8 +/- 8%, versus 33 +/- 8% at baseline to 34 +/- 4% after placebo; p = 0.01), and reduced the mean maximal fall in FEV1 during the late response (24 +/- 20% at baseline to 9 +/- 10% versus 20 +/- 17% at baseline to 18 +/- 17% after placebo; p = 0.047). We conclude that an anti-IgE monoclonal antibody, which inhibits binding of IgE to its receptor, suppresses the early- and late-phase responses to inhaled allergen in allergic asthmatic subjects. Targeting IgE with rhuMAb-E25 might be a useful treatment for allergic asthma.

Generation, Persistence, and Modulation of Th0 Effector Cells: Role of Autocrine IL-4 and IFN-γ

Many studies have classified CD4 responses into either Th1-like or Th2-like, based on cytokine secretion profiles, but little significance has been placed on Th0 cells. This has largely resulted from studies that suggested that Th0 populations primarily comprise individual Th1 and Th2 cells. Here, we show that priming of Ag-specific naive CD4 cells with moderate dose IL-4 generates a Th0 population that is evident after 3 days in vitro and becomes prevalent after successive encounters with Ag over a 9-day period. By intracellular cytokine staining, the majority (&gt;60%) of effector cells generated in this way produce either IL-4, IFN-γ and IL-2, or IL-4 and IFN-γ without IL-2. Endogenous IFN-γ secreted over the initial 3 days of culture was critical for generating Th0 cells, since neutralization allowed IL-4 to induce differentiation into Th2-like cells. Successive encounters with Ag were required for generating Th0 cells, and their stability and persistence were governed by the balance of endogenous IL-4 and IFN-γ secreted during the later stages of differentiation. Studies blocking Fas-induced cell death showed that this process played no role in Th0 cell generation, and differential death of committed Th1 or Th2 cells was not required for Th0 persistence. These data suggest that Th0 cells can be as prevalent as Th1- or Th2-like cells after naive CD4 activation, that the relative levels of autocrine IL-4 and IFN-γ are important to the lack of commitment, and that not all cells are predestined to the Th1 or Th2 phenotypes early in the response.

The profile of the cytokines secreted during the generation of T-helper cells from atopic asthmatic subjects

This study investigated cytokine release by T-cell lines from atopic and nonatopic individuals in the presence of specific aeroallergen. Cell lines from atopic and nonatopic individuals secreted IL-2 for less than 14 and more than 21 days, respectively. All of the atopic, but not the nonatopic, cell lines exhibited a biphasic peak in IL-4 and IL-5 secretion. Flow cytometry revealed that, after 35 days, 89.3% of the atopic cells were T helpers and 73.2% were activated. Only 7.4% of the nonatopic cells displayed activation markers. In conclusion, T-cell differentiation may be controlled by other factors in addition to stimulation by aeroallergens.

Sequential production of IL-2, IFN-gamma and IL-10 by individual staphylococcal enterotoxin B-activated T helper lymphocytes

Upon primary activation, T helper (Th) cell populations express different cytokines transiently and with different kinetics. Stimulation of naive murine splenic Th cells with the bacterial superantigen Staphylococcus aureus enterotoxin B (SEB) in vitro results in expression of IL-2, IFN-gamma and IL-10 with fast, intermediate and slow kinetics, respectively. This first report of a functional analysis of cells separated alive according to cytokine expression shows that these cytokines are not produced by different Th cell subpopulations, but can be expressed sequentially by individual Th cells. Th cells, activated with SEB for 1 day and isolated according to expression of IL-2, using the cellular affinity matrix technology, upon continued stimulation with SEB later secrete most of the IFN-gamma and IL-10. Likewise, after 2 days of SEB culture, cells expressing IFN-gamma, separated according to specific surface-associated IFN-gamma as detected by magnetofluorescent liposomes, 1 day later secrete IL-10. Thus, individual Th1 cells can contribute to the control of their own IFN-gamma expression by sequential expression of first IL-2, supporting their proliferation, and later IL-10, down-regulating the production of IFN-gamma-inducing monokines and limiting the pro-inflammatory effects of IFN-gamma.

Alveolar macrophages from atopic asthmatics, but not atopic nonasthmatics, enhance interleukin-5 production by CD4+ T cells

Recent studies have demonstrated that different antigen-presenting cell (APC)-related factors in the microenvironment of a T cell may determine its profile and quantity of cytokine expression and production. We have therefore examined the effects of alveolar macrophages and peripheral blood monocytes on interleukin (IL)-5 production by peripheral blood CD4+ T cells from atopic people with asthma (AA), atopic people without asthma (AN), and nonatopic normal subjects (N). In response to allergen stimulation, IL-5 production was significantly enhanced by the addition of monocytes to CD4+ cell cultures in AA and AN patients (p < 0.05 and 0.01, respectively), but not in N subjects. In mitogen-stimulated CD4+ cell plus monocyte cocultures, there was a small increase in IL-5 production in all three groups (p < 0.05 for AN). In contrast, the addition of alveolar macrophages to parallel cultures significantly amplified IL-5 production only in AA patients (p < 0.05 or 0.01). Furthermore, IL-5 production by CD4+ cells in alveolar macrophage cocultures, stimulated by allergen or mitogen, was higher than that in monocyte cocultures in AA patients (p < 0.05). Conversely, in AN and N subjects, the IL-5 values for alveolar macrophage cocultures were lower than those for peripheral blood monocytes. In blocking studies, antibodies against IL-1alpha, IL-1beta, IL-6, or tumor necrosis factor-alpha differentially suppressed macrophage-enhanced IL-5 production (p < 0.05 for IL-1beta and IL-6) and expression of the activation marker CD25 (p < 0.05 for IL-1alpha and IL-6) by allergen-stimulated CD4+ cells in AA patients. These observations suggest that alveolar macrophages influence the quantity of IL-5 production by T cells in the airways and, as a consequence, the development of asthma in atopic individuals.

The Leishmania promastigote surface antigen-2 (PSA-2) is specifically recognised by Th1 cells in humans with naturally acquired immunity to L. major

The promastigote surface antigen-2 (PSA-2) is a Leishmania parasite antigen, which can induce Th1-mediated protection against murine leishmaniasis when used as a vaccine. To evaluate PSA-2 as a human vaccine candidate the specific T-cell response to PSA-2 was characterised in individuals immune to cutaneous leishmaniasis. Peripheral blood mononuclear cells from Sudanese individuals with a past history of self-healing cutaneous leishmaniasis proliferated vigorously in response to PSA-2 isolated from Leishmania major, whereas the antigen did not activate cells from presumably unexposed Danes. Peripheral blood mononuclear cells from individuals with previous L. major infection had varying proliferative responses to PSA-2 derived from L. donovani promastigotes. Peripheral blood mononuclear cells activated by PSA-2 from L. major produced high amounts of interferon-gamma and tumour necrosis factor-beta, and little interleukin-4, thereby showing a Th1 cytokine pattern. Parallel cultures showed clear Th1 and Th2 response patterns to purified protein derivative of tuberculin or tetanus toxoid, respectively. Flow cytometric analysis revealed that PSA-2 induced blastogenesis in the CD3 positive population and that these cells were the major source of interferon-gamma. The results show that Th1-like cells recognising PSA-2 are expanded during infection by L. major and that they maintain their Th1-like cytokine profile upon reactivation in vitro. Since immunity to cutaneous leishmaniasis is mediated by antigen-specific Th1-like cells, PSA-2 might be considered a vaccine candidate for human leishmaniasis.

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.

Evaluating the role of Th0 and Th1 clones in autoimmune thyroid disease by use of Hu-SCID chimeras

To study the role of Th0 and Th1 cells in autoimmune thyroid disease, thyroid tissues from patients with Graves' disease (GD), Hashimoto's thyroiditis (HT), and colloid nodular disease were xenografted into SCID mice, followed by ip injection of peripheral blood mononuclear cells (PBMC), T cell lines, and T cell clones (TCC). The antigen-specific TCC reactive to TSH receptor (TSH-R), thyroid peroxidase (TPO), or thyroglobulin (Tg), and their respective peptides, were classified into Th0 (secreting IL-4 and/or IL-5 and IFN-gamma) and Th1 (secreting IFN-gamma) according to their cytokine profile. Engraftment of autologous or HLA-matched allogeneic CD4+ thyroid-specific clones with Th0 or Th1 phenotypes induced the production of total IgG and thyroid-specific autoantibodies by B cells present in xenografted thyroid tissues. TSH-R-specific clones mainly enhanced thyroid-stimulating antibodies (TSAb) production, while clones reactive to TPO and Tg increased the synthesis of TPO and Tg autoantibodies. Total IgG production, but not TSAb, was also stimulated by PBMC and TSH-R lines. TSAb correlated with the viability and hyperplasia of thyroid follicles, but not with the serum T3 levels, which were normal. Thyroid tissue viability was maintained or increased by antigen-specific Th0 clones, and decreased by Th1 clones reactive to TSH-R or TPO. Thyroid lymphocytic infiltration was variable; however, Th0 and Th1 clones from HT patients caused high degree of lymphocytic infiltration compared to the control groups. These results demonstrate for the first time that T cells clones reactive to specific epitopes of TSH-R, TPO, or Tg can generate antibody-mediated and/or cell-mediated responses in the xenografted thyroid tissue microenvironment. Such effects depend on clonal specificity, HLA class II restriction, and cytokine profile of the clone. Th0 clones reactive to TSH-R stimulate both total IgG production and TSAb in SCID mice engrafted with thyroid tissue from GD patients. Th0 and Th1 clones specific for TPO and Tg also function as helper T cells, stimulating total IgG synthesis and autoantibodies against TPO and Tg. Th1 clones may also cause tissue destruction in GD and HT.

Relationship between IL-4 and IL-5 mRNA expression and disease severity in atopic asthma

Atopic asthma is characterized by chronic inflammation of the bronchial mucosa in which eosinophil- and immunoglobulin E (IgE)-dependent mechanisms are believed to be prominent. Therefore, specific proeosinophilic mediators such as interleukin (IL)-5 and essential cofactors for IgE switching in B-lymphocytes such as IL-4 could play a pivotal role in asthma. However, the exact role that individual inflammatory mediators play in the development of the disease in humans is still unknown. Using semiquantitative reverse transcriptase-polymerase chain reaction amplification in bronchial biopsies from 10 atopic asthmatics, we have tested the hypothesis that IL-4 and IL-5 mRNA expression relative to beta-actin mRNA correlates with validated indicators of disease severity. IL-4 and IL-5 mRNA copies relative to beta-actin mRNA were detected in bronchial biopsies from atopic asthmatics. The numbers of IL-5 mRNA copies relative to beta-actin mRNA correlated with disease severity assessed by the Aas asthma score (r = 0.70, p = 0.01), baseline FEV1 (r = -0.94, p = 0.001), baseline peak expiratory flow rate (r = -0.77, p = 0.01), peak expiratory flow rate variability over 2 wk (r = 0.69, p = 0.028), and the histamine PC20 (r = -0.72, p = 0.018). Conversely, the numbers of IL-4 mRNA copies relative to beta-actin mRNA did not correlate with asthma severity, but they positively correlated with total serum IgE concentrations (r = -0.90, p = 0.001). Our present results support the concept that IL-5 may determine asthma clinical expression and severity, and by inference they support the development of IL-5 targeted therapies.

Increased levels of IL-4 in CD8+ T cells in atopic asthma

BACKGROUND

In view of reports that CD8+ T cells may produce T(H2)-type cytokines and our own finding that levels of intracellular IL-4 are higher in CD8+ than CD4+ T cells in healthy nonatopic subjects, we have hypothesized that the capacity of CD8+ T cells to produce IL-4 may be increased in atopic asthma, a disease characterized by high production of T(H2) cytokines.

METHODS

Levels of IL-4 and interferon-gamma were measured by ELISA in cell lysates and in 20- and 48-hour cultures of concanavalin A-stimulated purified peripheral blood CD8+ T cells in seven patients with mild atopic asthma and seven healthy nonatopic subjects.

RESULTS

Resting CD8+ T cells in patients with asthma contained significantly more IL-4 than those of healthy nonatopic subjects (median, 26 pg/10(6) cells; range, 17 to 84 pg/10(6) cells vs 16 pg/10(6) cells; 10 to 28 pg/10(6) cells), with no difference in intracellular interferon-gamma levels. In the healthy control subjects, but not in the patients with asthma, levels of intracellular IL-4 correlated negatively with levels of interferon-gamma in resting CD8+ T cells (r[s] = -0.9411, p = 0.005). Stimulation with concanavalin A produced a consistent and significant increase in secretion of interferon-gamma, but not IL-4, with no difference between the two groups of subjects.

CONCLUSION

The results of this study suggest that CD8+ T cells from patients with asthma may be an important source of the T(H2)-type cytokine IL-4. This capacity appears to be acquired in vivo, possibly by conditioning by IL-4 produced in the inflamed airways.

Demonstration of the Th1 to Th2 cytokine shift during the course of HIV-1 infection using cytoplasmic cytokine detection on single cell level by flow cytometry

OBJECTIVE

To characterize changes of Th1/Th2 cytokine production by peripheral blood mononuclear cells (PBMC) that occur during the course of HIV infection by cytoplasmic cytokine staining on single cell level.

DESIGN AND METHODS

Mitogen-stimulated PBMC from 16 healthy donors, 18 HIV-1-infected individuals without AIDS and 14 patients with AIDS were stained intracellularly with fluorescein-labelled MAb against interleukin (IL)-2, IL-4, IL-10 and interferon (IFN)-gamma. Additionally, co-staining of CD4+ T-cell, CD8+ T-cell, natural killer (NK) cell, B-cell and monocytic markers was performed. Fluorescence staining was analysed by three-colour flow-cytometry.

RESULTS

A reduced percentage of IL-2 and IFN-gamma (Th1 type)-producing cells among CD4+ T cells from HIV-1-infected individuals could be demonstrated. There was a continuous decrease of IFN-gamma-producing CD4+ T cells in the course of HIV infection and a dramatic reduction of IL-2-expressing cells among CD4+ T cells in patients with AIDS. In contrast to Th1 cytokines, the frequency of Th2 cytokine expressing cells among CD4+ T cells increased in HIV-infected individuals. The maximum frequency of IL-4-expressing cells among CD4+ T cells was seen in HIV-infected individuals without AIDS, whereas the rate of IL-10-producing cells was highest in patients with AIDS. In HIV-infected individuals no significant proportion of Th0 cells expressing both Th1 and Th2 cytokines was detectable. In CD8+ T cells the percentage of IL-2 was expressing cells decreased continuously accompanied by a strong increase of the frequency of IFN-gamma-producing cells.

CONCLUSION

The decreased percentage of cells expressing IL-2 and IFN-gamma in conjunction with an increased proportion of IL-4- and IL-10-producing cells among the CD4+ T cells in HIV-1-infected individuals demonstrate a Th1 to Th2 cytokine shift in the course of HIV infection on a single cell level. There was no evidence of a Th1 to Th0 cytokine shift. In addition to the loss of CD4+ T cells in HIV infection, the qualitative changes of Th1/Th2 cytokine expression may serve as a marker for progressive failure of cell-mediated immunity.

CD4+ CD7- T cells: a separate subpopulation of memory T cells?

The CD7 molecule is apparently involved in T cell activation but is absent in a substantial subpopulation of human T cells under physiological and certain pathological conditions. The majority of CD7- T cells expresses TCR alpha/beta and is of CD4+ helper and CD45R0+CD45RA- memory phenotype. After birth, percentages and absolute numbers of circulating CD7- T cells increase significantly during aging. A number of molecules thought to be involved in organ-specific T cell homing are preferentially expressed within the subset of CD4+CD7- T cells. Specific absence of CD7 antigen expression on T cells is observed in a variety of pathologic conditions such as cutaneous T cell lymphoma, HIV infection, rheumatoid arthritis, and kidney transplantation. Current in vitro results suggest that specific downregulation of CD7 antigen expression in T cells reflects a separate and stable differentiation state occurring late in the immune response. Expansion of CD7- T cells in vivo has been found in certain diseases associated with chronically repeated T cell stimulation. The potential pathophysiological significance of this T cell subset in certain human diseases is discussed.