Specific induction of interleukin-4-producing cells in response to in vitro allergen stimulation in atopic individuals

Background and Objective CD4⁺ T cells can be divided into two major subsets. T helper (TH)₁ and TH₂ cells. Interleukin-4 (IL-4) is produced by TH₂ cells and induces switching of immunoglobulin (Ig) M/lgG to IgE. Interferon-γ (IFNγ) produced by TH₁ cells counteracts the IgE-promoting effects of IL-4. In this study we wanted to investigate whether the number of IL4-producing cells could be a direct measurement of allergen exposure in vitro, and whether this was correlated to the elevated serum IgE-levels seen in atopic persons. Methods We compared the number of IL-4- and IFNγ-producing cells using an enzyme-linked immunospot assay (ELISPOT) in response to allergens from birch and cat in peripheral mononuclear cells from atopic and healthy individuals. Results In the two sensitized groups there was an increase in the number of lL-4producing cells in response to the specific allergen which was not seen in the healthy group (1/20000 cells and 1/200 000 cells, respectively, P < 0.001 for birch). In criss-cross experiments where birch-sensitized individuals were stimulated with cat allergen, no lL-4-producing cells were seen, indicating a high degree of specificity. In individual subjects, the elevated numbers of IL-4-producing cells were significantly correlated with their allergen-specific serum IgE levels. When allergen was combined with a suboptimal dose of PHA, there was a synergistic increase in the number of allergen-induced IL-4-producing cells (1/4000 cells) in the atopic donors, which was not seen with the number of IFNγ-producing cells. Conclusions Allergen-specific IL-4 producing cells in a peripheral blood mononuclear cell (PBMC) culture can be detected by ELISPOT and the response can synergistically be enhanced by suboptimal concentrations of PHA.     

Role of interleukin 4 and gamma interferon in the regulation of human IgE synthesis: possible alterations in atopic patients

The IgE helper function of human T cell clones or their phytohemagglutinin-induced supernatants was positively correlated with their ability to produce or their content in interleukin 4 (IL-4), whereas it was inversely correlated with production of or content in gamma interferon. The addition to B cell cultures of anti-IL-4 antibody abolished not only the IgE synthesis induced by recombinant human IL-4, but also that induced by IL-4-producing T cell clones or their phytohemagglutinin-induced supernatants. A clonal analysis in nonatopic donors and patients with common atopy showed that atopics possess in their peripheral blood significantly higher numbers of T cells able to secrete IL-4 and to provide helper function for IgE.     

Effects of interferon-α on cytokine profile,T cell receptor repertoire and peptide reactivity of human allergen-specific T cells

A large panel of T cell clones (TCC) specific for the recombinant form of Poa pratensis allergen (rKBG7.2 or Poa p9) were established from the peripheral blood of a grass pollen-sensitive donor in the absence or presence of recombinant interferon-α (IFN-α) in bulk culture and their pattern of cytokine secretion, peptide reactivity and TCR Vβ repertoire was examined. The majority of allergen-specific TCC derived in absence of IFN-α produced high amounts of interleukin-4 (IL-4) and IL-5 but not IFN-γ (Th2 cells), while most of TCC derived in presence of IFN-α produced IFN-γ but not, or limited amounts of, IL-4 and IL-5 (Th1 or Th0 cells). Of 24 TCC established in the presence of IFN-α, 22 were able to recognize a single allergen peptide, p26, while none of the clones established in the absence of IFN-α showed a similar specificity. The majority of both clones expressed the Vβ2 element regardless of whether they were established in the presence of IFN-α, but the presence of IFN-α favored the expansion of Vβ2⁺, Vβ17⁺ and Vβ22⁺ Poa p9-specific T cells, whereas in the absence of IFN-α, other TCR Vβ-bearing T cells (Vβ5, Vβ6.7 and Vβ14) were expanded in addition to Vβ2⁺ T cells. None of Vβ2⁺ clones established in the absence of IFN-α reacted with p26, whereas all the Vβ2⁺ clones established in its presence responded to this peptide. IFN-α also shifted the TCR Vβ repertoire of both Poa p9- and Lolium perenne group 1 (Lol p1)-specific T cell lines generated from the same patient and from a different grass-sensitive individual. These data demonstrate that IFN-α modulates the development of allergen-specific T cells in vitro, and suggest that IFN-α may represent an useful tool for novel immunotherapeutic approaches in allergic disorders.     

Human dendritic cells transfected with allergen-DNA stimulate specific immunoglobulin G4 but not specific immunoglobulin E production of autologous B cells from atopic individuals in vitro

Atopic/allergic diseases are characterized by T helper 2 (Th2)-dominated immune responses resulting in immunoglobulin E (IgE) production. DNA-based immunotherapies have been shown to shift the immune response towards Th1 in animal models. In further studies we showed that human dendritic cells (DC) transfected with allergen-DNA are able to stimulate autologous CD4(+) T cells from atopic individuals to produce Th1 instead of Th2 cytokines and to activate interferon-gamma (IFN-gamma)-producing CD8(+) T cells. The aim of this study was to analyse whether DC transfected with allergen-DNA are also able to influence immunoglobulin production of B cells from atopic donors. For this purpose, human monocyte-derived DC from grass-pollen allergic donors were transfected with an adenovirus encoding the allergen Phleum pratense 1 and cocultured with B cells, autologous CD4(+) T cells, and CD40 ligand-transfected L-cells. B cells receiving help from CD4(+) T cells stimulated with allergen-transfected dendritic cells produced more allergen-specific IgG4 compared to stimulation with allergen protein pulsed DC or medium, while total IgG4 production was not affected. In contrast, specific IgE production was not enhanced by stimulation with allergen-DNA transfected DC compared to medium and inhibited compared to allergen protein-pulsed DC with similar effects on total IgE production in vitro. Allergen-DNA transfected dendritic cells are able to direct the human allergic immune response from Th2-dominance towards Th1 and Tc1 also resulting in decreased IgE and increased IgG4 production.     

Relationship between facilitated allergen presentation and the presence of allergen-specific IgE in serum of atopic patients.

Allergen presentation to allergen-specific T cells can be facilitated when IgE-allergen complexes are endocytosed by antigen-presenting cells (APC) after binding to the low-affinity Fc epsilon R type II (CD23). Here we present a study on the relative capabilities of sera of atopic patients to mediate facilitated antigen presentation (FAP). To this aim FAP was studied in an in vitro model in which CD23-expressing Epstein-Barr virus (EBV)-B cells act as APC to T lymphocyte clones (TLC) that are specific for Der p 2, a major allergen of housedust mite Dermatophagoides pteronyssinus (Dp). Der p 2 is immune-complexed by preincubation in sera from atopic patients, containing allergen-specific IgE. If EBV-B cells are preincubated with these complexes before using the cells as APC, the allergen-specific TLC proliferate at 100-1000-fold lower allergen concentration than required for T cell activation after presentation of uncomplexed allergen. The relative capability of various sera to mediate FAP was correlated with total serum IgE, and especially with Der p 2-specific serum IgE. In the model used, a high FAP capacity could be demonstrated only in sera with a total serum IgE concentration above approximately 2 micrograms/ml or with Der p 2-specific IgE above approximately 100 ng/ml. Maximal FAP, i.e. the ability to induce maximal proliferation of the TLC, was obtained in the presence of more than +/- 600 ng Der p 2-specific IgE/ml. At 100-600 ng/ml Der p 2-specific IgE the level of FAP was correlated with the concentration of allergen-specific IgE, whereas at lower concentrations FAP was low or absent. All tested sera from eczema patients, all having serum anti-Der p 2-IgE concentrations > 600 ng/ml, showed a high FAP capacity, whereas all tested sera from atopic patients without eczema, which had serum anti-Der p 2-IgE levels < 600 ng/ml, showed no or a low FAP capacity. The association of high FAP capacity with eczema may reflect a functional role of FAP in the pathogenesis of atopic dermatitis.     

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-γ 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.     

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

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

Increased Frequencies of Allergen-Induced Interleukin-13-Producing Cells in Atopic Individuals During the Pollen Season

We have reported previously that allergen-specific serum IgE levels were correlated with allergen-induced interleukin (IL)-4 in type I allergic individuals. Here, we wanted to investigate whether IL-13, another switch factor for IgE, was induced by allergen in vitro and if so, whether this was correlated with the elevated serum IgE-levels seen in atopic individuals, and whether the cytokine profile changed during pollen season. Peripheral blood mononuclear cells from 14 atopic and 14 healthy individuals collected out of the pollen season were incubated in vitro with allergens (birch or timothy) and the number of IL-4, IL-13, IL-10 and IFN-γ producing cells was determined by ELISPOT. In response to the specific allergen, IL-13-producing cells were seen in allergic but not in healthy individuals. The number of IL-13-producing cells was significantly correlated with the allergen-specific serum IgE levels. When the allergic individuals were tested during the pollen season, the number of allergen-specific IL-4- and IL-13-producing cells, as well as serum levels of specific IgE, increased. The IL-13 increase seen in ELISPOT was confirmed by a RT–PCR assay. No seasonal changes were seen in response to purified protein derivative (PPD) or the mitogen PHA. During the pollen season, the IL-4 and IL-13 responses were highly correlated. Taken together, our results support the roles of both IL-13 and IL-4 in the regulation of allergen-specific IgE levels in atopic individuals.     

IL-10 production in circulating T cells differs between allergen-induced isolated early and dual asthmatic responders

BACKGROUND: IL-10 is an anti-inflammatory cytokine released from various cells, including T cells. The role of IL-10 in asthma pathogenesis remains uncertain. Allergen inhalation by atopic asthmatic subjects results in 2 bronchoconstrictor phenotypes: isolated early response and dual response. Persistence of allergen-induced airway inflammation is a feature of dual responders. OBJECTIVES: The kinetics of IL-10 production in circulating T cells were investigated to examine a potential role of IL-10 in allergen-induced responses and airway inflammation. METHODS: Fourteen subjects with mild asthma (7 isolated early and 7 dual responders) were challenged with allergen. PBMCs taken before and 24 hours after allergen challenge were processed for intracellular IL-10 staining with fluorescent-conjugated anti-IL-10 antibody. The frequency of IL-10-producing cells was assessed for CD4(+) and CD8(+) T-cell subsets by using flow cytometry. RESULTS: Before allergen administration, the frequency of IL-10-producing CD4(+) cells was significantly higher in dual than in isolated early responders. IL-10-producing CD4(+) cells significantly increased after allergen in early responders, whereas IL-10-producing CD4(+) cells significantly decreased in dual responders. Simultaneous assessments of IL-5-producing T cells did not show any differences between each group before or after allergen administration. CONCLUSIONS: These results suggest that the contrasting profiles of IL-10 production may be associated with the different time course of allergen-induced airway inflammation between allergen-induced early and dual responders.     

Bet v 1, the major birch pollen allergen, initiates sensitization to Api g 1, the major allergen in celery: evidence at the T cell level

Due to IgE cross-reactivity, birch pollen-allergic individuals frequently develop type I hypersensitivity reactions to celery tuber. We evaluated the T cell response to the major allergen in celeriac, Api g 1, and the cellular cross-reactivity with its homologous major allergen in birch pollen, Bet v 1. Api g 1-specific T cell lines (TCL) and clones (TCC) were established from peripheral blood mononuclear cells of allergic patients. Epitope mapping of Api g 1 with overlapping Api g 1-derived peptides revealed one dominant T cell-activating region, Api g 1(109-126). TCL and TCC generated with Api g 1 cross-reacted with the birch pollen allergen and, although initially stimulated with the food allergen, cellular responses to Bet v 1 were stronger than to Api g 1. Epitope mapping with Bet v 1-derived peptides revealed that T cells specific for several distinct epitopes distributed over the complete Bet v 1 molecule could be activated by Api g 1. Bet v 1(109-126) was identified as the most important T cell epitope for cross-reactivity with Api g 1. This epitope shares 72% amino acid sequence similarity with the major T cell-activating region of the food allergen, Api g 1(109-126). Our data provide evidence that humoral as well as cellular reactivity to the major celery allergen is predominantly based on cross-reactivity with the major birch pollen allergen. The activation of Bet v 1-specific Th2 cells by Api g 1, in particular outside the pollen season, may have consequences for birch pollen-allergic individuals.     

House dust mite-specific T cells in the skin of subjects with atopic dermatitis: frequency and lymphokine profile in the allergen patch test.

The mechanism underlying positive patch tests with house dust mite-allergen, Dermatophagoides pteronyssinus (Der p), in patients with atopic dermatitis was investigated by isolating T cells from the test sites of two patients. Eighty-five T cell clones (TCC) were established from the epidermis and dermis of lesional skin by the limiting-dilution method with Der p and interleukin (IL)-2. With restimulation assays, 29 of 60 TCCs tested demonstrated specific proliferation; 85% were of the CD3+, CD2+, and CD4+ phenotype. Der p-specific T cells constituted 0.4% to 2.7% of lesional T cells, and they were more frequent in the skin than in the blood of the patients by one order of magnitude. The mitogen-stimulated lymphokine profile of 55 TCCs was assessed; 42% (11/26) of the allergen-specific TCCs secreted IL-4 but almost no interferon-gamma, as described for the Th2 subset of the mouse. Also, six selected TCCs supported IgE secretion by autologous lymphocytes. Only three of 26 allergen-specific, skin-derived TCCs demonstrated a Th1-like lymphokine profile. These results support the specific nature of Der p-induced patch test lesions in patients with atopic dermatitis, and the results demonstrate also that a considerable proportion of lesional T cells are allergen-specific, IL-4-producing T cells that are capable of enhancing IgE production.     

Different growth factor requirements for human Th2 cells may reflect in vivo induced anergy.

We previously reported the isolation of allergen-specific Th2 lines and clones from atopy patch test (APT) sites of atopic dermatitis (AD) patients. Upon stimulation with allergen or anti-CD3+ phorbol myristate acetate (PMA) IL-4 was released with or without IL-5, while no (or extremely low concentrations of) IL-2 and interferon-gamma (IFN-gamma) were detectable. A high IL-4/IFN-gamma ratio facilitates production of allergen-specific IgE, of which high levels are observed in AD patients. Here we show that the above mentioned Th2 cells are notably different from murine Th2 cells. Not IL-4, which is the autocrine acting growth factor for murine Th2 cells, but IL-2 was needed for proliferation of these human APT-derived Th2 lines and clones. Of significance, unless exogenous IL-2 was added, no proliferative response to allergen, presented by Epstein-Barr virus-transformed B (EBV-B) cells, non-T cells or IgE-bearing Langerhans cells (LC), occurred. Lack of proliferation and IL-2 production after full T cell receptor (TCR) triggering is a characteristic first described for in vitro anergized T cells. However, like the clones we describe in this study, anergic T cells may retain production of cytokines other than IL-2. A further resemblance between anergic T cells and the human Th2 clones reported here is that IL-4 can enhance IL-2-driven proliferation, but is not capable of inducing T cell growth by itself. The absence of IL-4-driven proliferation differentiates human Th2 cells from murine Th2 cells. Both produce IL-4 when stimulated in a cognate fashion, but only murine Th2 cells will proliferate. We conclude that the presently reported human Th2 cells are different from murine Th2 cells, in that they need other T cells to produce IL-2 required for their expansion. Moreover, the Th2 cells phenotypically resemble anergic T cells. As yet, however, we have no clue as to whether these features account for the current Th2 cells only or for human Th2 cells in general. We hypothesize that the Th2 phenotype of AD skin-derived, allergen-specific T cells may be induced in vivo by LC, which lack CD80, and therefore do not provide secondary signals through CD28-CD80 interaction.     

Th1/Th2 profile in peripheral blood in atopic cough and atopic asthma

BACKGROUND: Eosinophilic tracheobronchitis with cough hypersensitivity, abbreviated as atopic cough, is an important cause of chronic cough. The reason for the absence of airway hyper-responsiveness is unknown, differing from asthma, a Th2 cytokine-mediated disorder. OBJECTIVE: To compare the type 1 helper T cell (Th1)/Th2 balance in the peripheral blood from subjects with atopic cough and atopic asthma, we assessed the intracellular cytokine production at the single-cell level. METHODS: Thirty-six subjects (10 patients with atopic cough, 18 with atopic asthma, and eight control subjects) were included. Intracellular IL-4 and IFN-gamma were detected in CD4+ T cells by flow cytometry. RESULTS: A significantly lower ratio of IFN-gamma-/IL-4-producing CD4+ T cells after phorbol 12-myristate acetate/ionomycin stimulation was found in patients with atopic cough and atopic asthma compared with normal subjects. In comparison between atopic patients, the ratio of IFN-gamma-/IL-4-producing cells was significantly higher in atopic cough than in atopic asthma. However, the proportion of IL-4-producing CD4+ T cells was significantly higher in patients with atopic asthma than in normal control subjects and no significant difference was detected between patients with atopic cough and normal subjects. No significant difference in the proportion of IFN-gamma-producing cells was found between the subjects. Overall, the total IgE levels were positively correlated to the IL-4-producing cells and inversely correlated to the ratio of IFN-gamma-/IL-4-producing cells. CONCLUSION: These results show the lower degree of Th2 cytokine predominance in atopic cough compared with atopic asthma and suggest the relation between the Th1/Th2 balance and atopic status.     

Interleukin-12 increases interleukin-4 production by established human ThO and Th2-like T cell clones

Interleukin (IL)-12 is a potent inducer of cell-mediated immunity: it favors the generation of interferon (IFN)-γ-producing T cells, increases IFN-γ production by T cells and natural killer cells and prevents the generation of a Th2 response in murine in vivo models. Nevertheless, the effects of IL-12 on an established Th2 response remain poorly documented. In the present paper, we analyzed the effect of IL-12 on the profile of lymphokines produced by established IL-4-producing Th0 and Th2-like human T cell clones (TCC) and by polyclonal T cells. We found that IL-12 (i) enhances, as previously reported, IFN-γ production by Th0 TCC and, to a smaller extent, by Th2-like TCC, (ii) increases the proliferation of Th0 and Th2-like TCC and (iii) unexpectedly, synergizes with T cell receptor-associated or nonspecific stimuli in increasing IL-4 production by these TCC. Thus, IL-12 potentiates the production of IFN-γ and also of IL-4 by established IL-4-producing TCC. Although IL-12 has been widely reported to induce a Th1 response and to prevent the development of a Th2 response in vivo, IL-12 may on the contrary potentiate an established Th2 response in humans.     

An in vitro model of allergen-dependent IgE synthesis by human B lymphocytes: comparison of the response of an atopic and a non-atopic individual to Dermatophagoides spp. (house dust mite).

An allergen-dependent in vitro model of immunoglobulin E (IgE) synthesis by human B cells is reported. Using this model, it is demonstrated that polyclonal T cells and CD4+ Dermatophagoides spp. (house dust mite)-specific T-cell clones derived from an atopic, house dust mite (HDM)-allergic individual are able to support IgE synthesis by autologous B cells. The helper activity was interleukin-4 (IL-4) dependent as only cloned T cells expressing detectable mRNA for IL-4 were able to induce IgE synthesis without the addition of exogenous IL-4. Peripheral and cloned T cells reactive with HDM could also be identified from a non-atopic individual but neither population was able to support IgE production even in the presence of exogenous IL-4.     

Elevated plasma levels of IgE in Plasmodium falciparum-primed individuals reflect an increased ratio of IL-4 to interferon-gamma (IFN-γ)-producing cells

People living in Plasmodium falciparum-endemic areas frequently have elevated levels of total as well as P. falciparum-specific serum IgE. This study aimed at investigating whether the elevated serum IgE levels reflect a shift in the balance between CD4⁺ T helper 1 (Th1) and T helper 2 (Th2) cells in individuals naturally exposed to the P. falciparum parasite. To investigate the role of Th1 and Th2 cells in the human P. falciparum system we used the ELISPOT assay to determine the ratio of IFN-γ- and IL-4-producing cells after specific antigen or mitogen activation in vitro. The donors were individuals who had acquired immunity through natural exposure to the parasite. In response to the specific malaria antigens, very few IL-4-producing cells were seen. However, in the response of individual donors to the polyclonal T cell activator, leucoagglutinin (La), the anti-malarial IgE levels in plasma were correlated with an increased ratio of IL-4/IFN-γ producing cells. Thus, donors with ratios of IL-4/IFN-γ > 1 exhibited mean plasma anti-malarial IgE levels significantly greater than those with ratios < 1. In individuals not living in P. falciparum-endemic areas the ratio of IL-4/IFN-γ was always < 1. Taken together, our data suggest a shift in the balance between Th1 and Th2 cells in naturally P. falciparum-primed individuals, associated with elevated anti-P. falciparum plasma IgE levels. The role and biological significance of IgE (Th2-type immune response) for protection against P. falciparum and/or pathogenesis of malaria require further study.     

Human γδ T cells modulate the mite allergen-specific T-helper type 2-skewed immunity

BACKGROUND: Gammadelta T cells have been described as one of immune regulators in patients with infection, malignancy, and allergy. OBJECTIVE: To elucidate the ability of gammadelta T cells as an allergen immunotherapy candidate, the effectiveness of human gammadelta T cells in allergen-specific T-helper type 2 (Th2)-type T cells was evaluated in vitro. METHODS: House dust mite-specific Th2-type T cell clones, Bacillus Calmette-Guerin (BCG)-specific Th1-type T cell clones, and gammadelta T cell lines were established from the peripheral blood mononuclear cells of two patients with allergic rhinitis. The effectiveness of gammadelta T cells and BCG-specific Th1-type T cell clones in the modulation of allergen-specific Th2 cells in terms of their cytokine productions was evaluated. RESULTS: In response to cognate antigens, the gammadelta T cell lines demonstrated a proliferation and production of IFN-gamma that exceeded that of BCG-specific Th1-type T cell clones (mean stimulation index: 14.5 vs. 2.8, mean IFN-gamma: 130.5 vs. 10.0 pg/mL). When the gammadelta T cell lines and mite-allergen-specific Th2 clones were co-cultured with each other, only the levels of IL-4 (mean, -87%) decreased, but not the levels of IL-5 and IL-13, with an increasing concentration of gammadelta T cell antigen and IFN-gamma production (mean, +730%). CONCLUSION: These results demonstrated that gammadelta T cells derived from allergic patients might thus have a partial ability to modulate allergen-specific Th2-skewed immunity.     

Functional heterogeneity of human T cell clones from atopic and non-atopic donors.

Several distinct T helper (TH) subsets have been identified, based on the cytokines secreted. Recently, it has been demonstrated that these subsets can regulate the isotype of humoral responses. To investigate the possible differences in TH subsets between atopic donors which have elevated serum IgE and donors with normal serum IgE, we examined series of human TH cell clones. A total of 31 and 22 CD4+ T cell clones from the atopic and non-atopic donors, respectively, were characterized for the ability to help for IgE synthesis in vitro. T cell clones generated with allergen AgE from the atopic donor were autoreactive and all induced IgE synthesis. Tetanus toxoid-specific (TT) and phytohaemagglutinin clones were generated from both donors. There was significant heterogeneity between the T cells isolated with different stimuli from the same atopic donor. Also, there was a significant difference in the number of T cells generated from the atopic versus the non-atopic donor which helped for IgE, although there was no significant difference between the total number of T cells able to help for immunoglobulin synthesis of other isotypes. Most importantly, there was a higher frequency of clones able to support IgE synthesis between TT-specific T cell clones generated from the atopic versus the non-atopic donor. These results suggest that there are changes in subsets of TH cells specific for microbial antigens as well as allergens in atopics, which may have important implications for the aetiology of atopic disease.