Regulation of the human IgE antibody response

In childhood asthma the degree of allergen-induced T-lymphocyte proliferation is related to serum IgE levels and to blood eosinophilia

OBJECTIVE

To investigate whether the state of activation of circulating T-cells in childhood asthma could be related to serum IgE levels and/or to blood eosinophilia.

METHODS

Seventeen atopic asthmatic children, sensitized to Dermatophagoides pteronyssinus (Der p), in stable condition at the time of the study and 15 sex-matched and age-matched controls were studied. The expression of activation surface markers (HLA-DR and CD25) on peripheral blood mononuclear cells (PBMCs) was tested by monoclonal antibodies and FACS analysis, while the PBMC proliferative response to Der p antigens was measured by tritiated thymidine (3HTdR) incorporation.

RESULTS

As compared to controls, atopic children showed higher eosinophil counts (P < .01), similar lymphocyte counts (P > .1, each comparison) but higher proportion of HLA-DR+ and CD25+ T-lymphocytes (P < .05, each comparison). A significant Der p allergen-induced PBMC proliferation was observed in atopic children (P < .01) but not in controls (P > .1). Both in controls and in atopic children, no correlations were found between lymphocyte counts and eosinophil counts or total or allergen-specific IgE levels (P > .1, each comparison). In contrast, weak correlations were detected between the degree of allergen-induced PBMC proliferation and: a) allergen-specific IgE levels in serum (P < .05) and b) eosinophil counts (P < .05).

CONCLUSION

These data support the concept that the degree of activation of allergen-specific T-lymphocytes in blood may reflect the intensity of allergic sensitization in childhood asthma.

Allergic inflammation in upper and lower airways

OBJECTIVE

The primary reason for this review is to discuss the relationship between upper and lower airways at various levels with the emphasis on common pathophysiologic mechanisms, and how treatment of the upper airways will benefit the lower airways.

DATA SOURCES

The main source of information is derived from original articles and books, with an extensive bibliography included.

STUDY SELECTION

Studies were derived almost exclusively from articles and reviews in peer-reviewed journals.

RESULTS

The prevalence of rhinitis and asthma are both increasing. Common to both the upper and lower airways are the triggers, many of the inflammatory cells and mediators, and the treatment modalities. By contrast, there are organ-specific differences in the reaction to various stimuli in the nose or lung, with each organ manifesting its own vocabulary of response.

CONCLUSIONS

There are meaningful relationships between upper and lower airways at various levels of our understanding. Differential responses to medications help us better understand pathogenic mechanisms in rhinitis and asthma. Further, treatment of the upper airways provides additional benefit to the lower airways.

Specific immunoglobulin E, interleukin-4, and soluble vascular cell adhesion molecule-1 in sera in patients with seasonal allergic rhinitis

This study included 23 nonatopic volunteers and 84 patients with seasonal allergic rhinitis due to Japanese cedar pollen. Serum interleukin-4 (IL-4) and soluble vascular cell adhesion molecule-1 (sVCAM-1) in the patients were significantly higher than those in the nonatopic individuals, even outside of the pollen season. Both the good responders and the poor responders to antihistamine tablets showed significant increases in IL-4 and specific IgE during the pollen season, whereas such seasonal increases were not observed in the good responders to immunotherapy. Seasonal increases in IL-4 were significantly correlated with those of specific IgE. However, seasonal increases in sVCAM-1 were not significant. Seasonal increases in sVCAM-1 were not significantly different between the good responders and the poor responders to pharmacotherapy or immunotherapy. In conclusion, serum IL-4 and sVCAM-1 are increased in patients with seasonal allergic rhinitis, even outside of the pollen season; this finding might suggest underlying preponderant in vivo activation of T helper cell-2-like cells and inflammatory events in seasonal allergic rhinitis. A seasonal increase in IL-4 in sera might be at least partly involved in the seasonal increase in specific IgE in sera. Immunotherapy's inhibitory effect on IL-4 production and specific IgE response might be one of its working mechanisms.

Seasonal changes in phytohemagglutinin-induced cytokine synthesis by peripheral blood lymphocytes of patients with seasonal allergic rhinitis due to Japanese cedar pollens

We investigated the seasonal changes in non-specific stimulation-induced cytokine production by peripheral blood mononuclear cells (PBMCs) in patients with seasonal allergic rhinitis due to Japanese cedar pollen. This study included 16 non-allergic healthy adult volunteers and 115 patients with detectable levels of Japanese cedar pollen-specific IgE in their serum. The 115 patients were divided into five groups, an asymptomatic group (specific IgE was positive but there were no nasal symptoms), a medication group (typical symptoms of Japanese cedar pollinosis and treated with antihistamine tablets), a good-IT group (responded well to immunotherapy), a poor-IT group (responded poorly to immunotherapy) and a cure group (no symptoms after discontinuation of immunotherapy). PBMCs (1.0 x 10(6) cells/ml) were collected before and during the cedar pollen season in 1998, and were cultured for 24 h in the presence of 10 micrograms/ml phytohemagglutinin. The concentrations of IL-4, IL-5 and IFN-gamma in the culture supernatants were measured by an enzyme-linked immunosorbent assay. None of the levels of IL-4, IL-5 and IFN-gamma synthesized by PBMCs in the asymptomatic group, medication group, good-IT group, poor-IT group or cure group were significantly different from those in the non-atopic group. In the medication group, the synthesis of TH2-type cytokines (both IL-4 and IL-5), but not of TH1-type cytokine (IFN-gamma) was significantly increased during the pollen season compared with before the pollen season, whereas in the non-atopic group, the synthesis of IL-4, IL-5 and IFN-gamma did not differ significantly before and during the pollen season. The synthesis of both IL-4 and IL-5 was significantly increased during the pollen season in the poor-IT group, whereas the synthesis of IL-4 and IL-5 was not increased during the pollen season in the good-IT or cure groups. In conclusion, our study demonstrates that T-cell reactivity to non-specific stimulation outside of the pollen season did not differ between the patients with seasonal allergic rhinitis and non-atopic individuals, that T-cells in patients with seasonal allergic rhinitis are affected or primed by the natural pollen exposure to synthesize TH2-type cytokines even in response to non-specific stimulation, and that successful immunotherapy could decrease the natural pollen exposure-primed hyperreactivity of TH2 cells to non-specific stimulants.

Suppression of seasonal increase in serum interleukin-5 is linked to the clinical efficacy of immunotherapy for seasonal allergic rhinitis

Although immunotherapy is recognized as a highly effective form of treatment for allergic rhinitis, especially pollen-induced seasonal allergic rhinitis, the mechanisms have not been fully established. In the present study, we investigated whether immunotherapy could affect the seasonal increase in interleukin-5 (IL-5) in the serum of patients with seasonal allergic rhinitis and whether the effect on IL-5 in serum is related to the clinical efficacy of immunotherapy. Venous blood was collected twice from each patient with seasonal allergic rhinitis due to Japanese cedar pollens, before and during the cedar pollen season in 1997, to determine the cedar pollen-specific IgE and IL-5 in serum. Both specific IgE and IL-5 in serum were significantly increased during the pollen season, not only in the poor responders to antihistamines but also in the good responders. Neither the rate of seasonal increase in specific IgE nor the rate of seasonal increase in IL-5 differed significantly between the good responders and the poor responders to antihistamines. Both specific IgE and IL-5 were significantly increased during the pollen season in the poor responders to immunotherapy, whereas neither specific IgE nor IL-5 was increased during the pollen season in the good responders to immunotherapy. The rate of seasonal increase in specific IgE as well as IL-5 was significantly smaller in the good responders than in the poor responders to immunotherapy. The rates of seasonal increase in specific IgE and in IL-5 were inversely correlated with the length of time on immunotherapy. However, the rate of seasonal increase in specific IgE was not significantly correlated with the rate of seasonal increase in IL-5. In conclusion, the suppression of the seasonal increase in IL-5 in serum is a working mechanism of immunotherapy related to the clinical efficacy of the treatment.

Allergen-specific immunotherapy for allergic rhinitis: a new insight into its clinical efficacy and mechanism

Immunotherapy has been used widely for allergic diseases for more than 90 years but, in the opinion of many physicians, it is still a controversial form of treatment. The exact mechanism of action of immunotherapy remains to be determined. In the present study, we review the clinical efficacy and mechanism of action of immunotherapy for allergic rhinitis. Recent double-blind placebo-controlled studies have demonstrated the clinical efficacy of immunotherapy for allergic rhinitis. This therapeutic method has several advantages over conventional pharmacological treatment. Immunotherapy is inferior to pharmacological treatment in the short term, but in the long term it is substantially superior with respect to clinical efficacy. Immunotherapy has the potential permanently to alleviate the abnormal immunological responses of allergic rhinitis and to cure the nasal symptoms in the long term, even after discontinuation of injections. In addition, immunotherapy can prevent the onset of new sensitizations in allergic patients and may prevent the progression of rhinitis to asthma. It may therefore be possible for immunotherapy to alter the natural history of allergic sensitization and its clinical manifestation. These lines of clinical evidence could affect strategies of long-term therapy for allergic rhinitis. Modern molecular biological techniques have suggested that immunotherapy may affect allergen-induced TH responses or cytokine profiles, but there is no general agreement among investigators. However, IL-5 is likely to be the most important cytokine involved in the clinical efficacy of immunotherapy, and the suppression of allergen-induced IL-5 synthesis is most likely to be involved in the mechanism of immunotherapy. Our recent investigations, focusing on specific IgE and IgG4 responses, suggest that immunotherapy-induced changes in these specific antibodies play a clinical role and are involved in the mechanism of action of immunotherapy. It is probable that immunotherapy modulates and affects many different immunological and non-immunological phenomena to produce clinical efficacy and that clinical improvement is a consequence of different mechanisms over time.

Immunotherapy suppresses both Th1 and Th2 responses by allergen stimulation, but suppression of the Th2 response is a more important mechanism related to the clinical efficacy of immunotherapy for perennial allergic rhinitis

Increased attention has recently been directed at the possibility that the clinical efficacy of immunotherapy might be elaborated by alteration of T-cell reactivity. However, there is no general agreement among different investigators regarding the effect of immunotherapy on Th-cell reactivity. Peripheral blood mononuclear cells (PBMCs) from 15 nonatopic subjects and 76 patients with perennial allergic rhinitis (18 untreated patients and 58 patients on immunotherapy) were cultured in the absence and in the presence of a major Dermatophagoides farinae allergen, Der f 1, and the levels of IgE, interleukin-5 (IL-5), interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) in the culture supernatants were determined. The difference between the absence and presence of Der f 1 was calculated to consider the Der f 1-dependent synthesis of IgE, IL-5, IFN-gamma and TNF-alpha. The levels of Der f 1-dependent synthesis of IgE, IL-5 and TNF-alpha were significantly higher in the untreated group than in the nonatopic group, whereas Der f 1-dependent synthesis of IFN-gamma was significantly lower in the untreated group than in the nonatopic group. Immunotherapy decreased the enhanced Der f 1-dependent synthesis of IgE, IL-5 and TNF-alpha, and further decreased the suppressed Der f 1-dependent synthesis of IFN-gamma as the therapy proceeded. The levels of Der f 1-dependent synthesis of IgE and IL-5 did not differ between nonatopic individuals and patients whose duration of immunotherapy was 10 or more years. The levels of Der f 1-dependent synthesis of IgE and IL-5, but not of IFN-gamma and TNF-alpha, were correlated significantly with the levels of symptom scores. In addition, the levels of Der f 1-dependent synthesis of IgE and IL-5, but not of IFN-gamma and TNF-alpha, differed significantly between good and poor responders. In conclusion, immunotherapy for perennial allergic rhinitis may possibly work via induction of tolerance or anergy of both Th1- and Th2 cells. However, our study is likely to support a view that the mechanisms responsible for the clinically beneficial effects of immunotherapy principally involve the tolerance of Th2- rather than Th1 cells. In addition, suppression of IgE synthesis is also likely to be linked to the clinical efficacy of immunotherapy for perennial allergic rhinitis.

Effects of long-term oral treatment with leflunomide on allergic sensitization, lymphocyte activation, and airway inflammation in a rat model of asthma

BACKGROUND

Short-term treatment with leflunomide is effective in suppressing antigen-specific antibody production and allergen-induced bronchoconstriction after sensitization. This agent may thus have a role in future primary prevention strategies in allergic disease.

OBJECTIVE

The current study aimed to determine whether long-term oral treatment with leflunomide prevents allergic sensitization permanently.

METHODS

After sensitization with ovalbumin, six groups of rats (n = 31) were treated daily with leflunomide or diluent for up to 30 days. Ovalbumin-specific IgE and IgG were determined weekly for at least 2 weeks after cessation of treatment. T lymphocytes from another 21 animals were stimulated ex vivo with ovalbumin or concanavalin A.

RESULTS

Ovalbumin-specific IgE and IgG were lower during treatment with leflunomide compared with controls (P < 0.002) but increased after the cessation of treatment. Antigen-specific T-cell proliferation was decreased in cells obtained from leflunomide treated animals (P < 0.05), but not when stimulated with concanavalin A. Eosinophil (P < 0.0001) and neutrophil (P < 0.02) numbers in bronchoalveolar lavage 24 h after allergen challenge were lower in the leflunomide treated animals.

CONCLUSIONS

Leflunomide prevents antigen-specific immunoglobulin production after sensitization during treatment, inhibits allergen-induced airway inflammation and diminishes antigen-specific T lymphocyte proliferation.

Seasonal rise in interleukin-4 during pollen season is related to seasonal rise in specific IgE for pollens but not for mites

Since IL-4 plays a key role in inducing and increasing the generation of not only primary polyclonal but also secondary specific IgE responses by B lymphocytes, a seasonal increase in IL-4 is likely to be involved in such seasonal rises in specific IgE in seasonal allergic rhinitis. The first aim of this study was to investigate the possible seasonal increase in serum IL-4 in patients with seasonal allergic rhinitis due to Japanese cedar pollens. If serum IL-4 increases in response to seasonal pollen exposure and is responsible for the seasonal increase in pollen-specific IgE in sera, this increase in IL-4 might theoretically affect specific IgE synthesis for other allergens. The second aim was to investigate the effect of natural pollen exposure on serum concentrations of house dust mite-specific IgE in patients who have seasonal allergic rhinitis and concurrent perennial allergic rhinitis due to house dust mites. This study included 55 adult patients with seasonal and perennial allergic rhinitis due to Japanese cedar pollens and Dermatophagoides farinae (D. farinae). Venous blood was collected twice from each patient, before and during the cedar pollen season 1996, to determine IL-4, cedar pollen-specific IgE and D. farinae-specific IgE in sera. Both IL-4 and pollen-specific IgE in sera were significantly increased during the pollen season, and the seasonal increase rate in pollen-specific IgE was significantly correlated with the seasonal increase rate in IL-4. By contrast, D. farinae-specific IgE was not changed during the pollen season in these patients. In conclusion, an elevation of IL-4 in sera during the pollen season may play an important part in the seasonal rise in pollen-specific IgE, and enhancement of specific IgE synthesis is likely to need not only an increase in IL-4 but also an increase in the number and/or capacity of specific IgE-secreting B cells.

Isolation of type 1 and type 2 cloned mite allergen-specific T cells from an asthmatic child

Allergen-specific T cells have been thought to play a central role in the pathogenesis of asthma. It has been well documented that allergen-specific T cells derived from atopic patients are predominantly of type 2 T helper cell pattern. However, allergen-specific T cells derived in nonatopic normals are of type 1 in contrast to atopic patients. The purpose of the study was to develop and characterize both mite allergen-specific TH1 and TH2 clones from the same asthmatic child. With exogenous supplemental cytokine, both TH1 and TH2 clones from the same patient have been developed and maintained in this laboratory for more than one year. All these T cell clones showed dose dependent allergen-specific proliferative response and expressed with CD4+, CD45RA- markers. Elucidation of the origin and interaction between these two different types of T helper cells might shed light on understanding the pathogenesis of atopic diseases and the mechanisms of hyposensitization in atopic patients.

BAL neutrophilia in asthmatic patients. A by-product of eosinophil recruitment?

Although neutrophil number may be increased in the airways of patients with asthma, its pathogenetic role in this disorder remains unclear. We evaluated BAL of 8 normal control subjects, 30 +/- 2 years of age, and 24 patients with mild asthma: 17 patients with allergic asthma, 24 +/- 1 years of age, and 7 patients with nonallergic asthma, 30 +/- 1 years of age. The BAL of asthmatic patients showed increased numbers of neutrophils (p < 0.01), eosinophils (p < 0.01), and ciliated epithelial cells (p < 0.05) and increased concentrations of myeloperoxidase (MPO) (p < 0.01) compared with control subjects. Positive correlations were observed between the number of BAL neutrophils and eosinophils (Rs = 0.780, p < 0.0001) and between BAL neutrophil numbers and BAL MPO levels (Rs = 0.40, p < 0.05). No correlations were found between the following: (1) BAL eosinophils or neutrophils and BAL epithelial cells (p > 0.05, each comparison); (2) BAL neutrophils or eosinophils and log Pd15 methacholine (MCh) (p > 0.05, each comparison); or (3) BAL epithelial cells or log Pd15 MCh and BAL MPO (p > 0.05, each comparison). Dividing the patient population into two groups, allergic asthmatics and nonallergic asthmatics, similar BAL neutrophil, eosinophil, and epithelial cell numbers and similar MPO levels were found (p > 0.05, each comparison). In addition, the correlations between BAL neutrophils and eosinophils showed similar significance in the two patient subgroups (p > 0.05, each comparison). These results suggest that, both in allergic and nonallergic asthma, airway recruitment and activation of neutrophils occur as does parallel eosinophil migration. However, airway neutrophils do not seem to contribute significantly to epithelial cell injury or to airway hyperresponsiveness in the steady state.

Cyclosporin A inhibits leukotriene production in intact RBL-1 cells without inhibiting leukotriene biosynthetic enzymes

The effects of cyclosporin A (CSA) on arachidonic acid (AA) metabolism were investigated in intact rat basophilic leukemia-1 (RBL-1) cells and cell lysates. Calcium ionophore (A23187)-stimulated synthesis of cysteinyl leukotrienes (LTC4, LTD4, and LTE4), LTB4, and 5-hydroxyeicosatetraenoic acid (5-HETE) in intact cells in the absence or presence of CSA was measured by reversed-phase high-performance liquid chromatography (HPLC). CSA inhibited the production of cysteinyl LTs, LTB4, and 5-HETE in intact cells in a dose-dependent manner. The synthesis of cysteinyl LTs, LTB4, and 5-HETE was also measured after the incubation of cell lysates with free AA in the absence or presence of CSA. CSA did not inhibit synthesis of cysteinyl LTs, but rather stimulated production of LTB4 and 5-HETE in cell lysate. A23187-stimulated release of incorporated [3H]AA from intact cells was not inhibited by CSA. CSA did not inhibit the synthesis of cysteinyl LTs and LTB4 when cells incubated with LTA4 as the substrate. These results indicate that the inhibitory effects of CSA on the synthesis of LTs and 5-HETE in intact cells are attributable to a modulatory action on a step in the series of intracellular events that includes the activation of 5-lipoxygenase, which are initiated by Ca2+ influx and end in the release of metabolites from the cell membrane, rather than to a direct inhibitory action on enzymes in the LT biosynthetic pathway.

Depletion of OX-8 lymphocytes from the blood and airways using monoclonal antibodies enhances the late airway response in rats

Recent evidence supports a role for T lymphocytes in allergic airway responses. We hypothesized that reducing blood T suppressor cells (Ts) might increase the late airway response (LR). Sprague-Dawley (SD) rats were sensitized with ovalbumin (OA). On days 8, 10, and 12, post-sensitization test SD (n = 14) received monoclonal antibody intravenously (OX-8; 1 mg) specific to rat Ts. Controls received saline (n = 7) or mouse ascites IgG (n = 7). On day 14, animals were challenged with OA aerosol (5% wt/vol) for 5 min, lung resistance was recorded for 8 h (n = 18) and bronchoalveolar lavage was performed. The LR was determined from the area under the lung resistance vs time curve from 75 to 480 min after challenge. In the remaining 10 rats, airway lymphocyte subsets were measured 8 h after OA aerosol challenge in minced and digested lungs. A decrease in percentage of blood and airway Ts, respectively, in test animals was observed vs controls (blood: 6.27 +/- 0.84 vs 32.95 +/- 1.94, P < 0.001); (airway: 5.05 +/- 0.66 vs 24.5 +/- 3.05, P < 0.02). Blood and airway helper T lymphocytes did not differ between test and control animals. The LR was significantly increased in test (22.89 +/- 3.92) vs controls (4.22 +/- 2.18, P < 0.001). Bronchoalveolar lavage macrophages, neutrophils and lymphocytes, and serum OA-specific IgE were also significantly elevated (P < 0.05) in test animals. We conclude that Ts play an important role in attenuating the LR in SD rats.

Current issues in the use of theophylline

Theophylline is a safe and effective medication for the management of chronic asthma. It reduces nocturnal bronchospasm and airways hyperresponsiveness, and its addition to effective doses of beta-agonists and corticosteroids leads to further improvement in symptom control. These properties are the result of actions other than simple bronchodilation, and there is a strong possibility that anti-inflammatory activity accounts for its clinical advantages. Serious side effects are uncommon and their rate can be further reduced through appropriate precautions. Recent studies have alleviated the concern over cognitive and behavioral side effects in children.

Atopic dermatitis: correlation of peripheral blood T cell activation, eosinophilia and serum factors with clinical severity

In the first part of this study peripheral blood lymphocyte subpopulations, their activation state and various serum parameters were measured in extrinsic and intrinsic atopic dermatitis (AD) patients compared to normal individuals. Beside the characteristic eosinophilia, significantly increased numbers of CD4+ T cells with increased expression of IL-2 receptors (IL-2R) and HLA-DR were noted in the AD patients. In addition, extrinsic AD patients showed increased numbers of CD23+ B cells and decreased numbers of CD16+ natural killer cells. Moreover, increased serum levels of eosinophil cationic protein (ECP) and soluble IL-2R as well as soluble factors that prolong survival of eosinophils in vitro could be demonstrated. In the second section of this study we determine how these blood immunological parameters relate to the clinical severity of the skin lesions of AD, by weekly analysis of 12 AD patients attending a high altitude clinic for 3 to 6 weeks. The patients were divided into two groups on the basis of treatment with topical steroids, but during the observation period a significant improvement in clinical status was observed in all AD patients independent of topical steroid therapy. A progressive decrease in eosinophil and activated T cell numbers, soluble IL-2R levels and serum eosinophil survival prolonging activity could be demonstrated, which closely correlated with the clinical severity of the AD.

Genetic 'risk' for atopy is associated with delayed postnatal maturation of T-cell competence

Recent in vitro studies suggest that IgE production in adults is co-ordinately regulated by negative signals from gamma IFN-producing CD4+ T-helper-1 (TH-1) and positive signals from IL-4 producing (TH-2) T-cells. Additionally, seroepidemiological evidence has pinpointed infancy as the period of maximum lifetime risk for T-cell sensitization to ubiquitous environmental antigens. The present study sought to elucidate the relationship between these observations, by examination of CD4+ T-cell function in normal children and those genetically at 'high risk' for atopy, spanning the age range (up to 4 years) in which IgE responses to environmental allergens is typically manifest. Immunocompetent T-cell precursor frequencies (determined by cloning at limiting dilution) were markedly reduced in 'high risk' children relative to normals (0.53 +/- 0.29 vs 0.26 +/- 0.19; P = 0.0025). Consistent with reports from other laboratories employing bulk T-cell culture techniques, the gamma IFN producing capacity of CD4+ T-cell clones from both groups of children were markedly reduced relative to adults, and was lowest in the high risk group (P < 0.02). IL-4 production by CD4+ T-cell clones from the normal children was within the adult range, but again was significantly lower in the high risk group (P < 0.00005). This indicates that initial immune responses to environmental allergens in early childhood occur against a background of maturational 'deficiency' in CD4+ T-cell function, and suggests the possibility that variations in the rate of postnatal maturation of T-cell competence may be a contributing factor in the development of differing patterns of immunological responsiveness to environmental allergens.

Major histocompatibility complex (MHC) class II restriction, lymphokine production, and IgE regulation of house dust mite-specific T-cell clones

To elucidate the regulatory mechanism of human IgE synthesis, we have cloned house dust mite (Dermatophagoides pteronyssinus; Dp)-specific T-cell clones from three asthmatic children and three healthy individuals. Twelve clones were cloned from each group. All of these clones were CD3+, CD4+, CD8-, and HLA-DR+. After stimulation with allergen in the presence of antigen presenting cells (APCs), half of the T-cell clones from asthmatic children and one-third of those from normals produced interleukin 4 (IL-4). None of the patients' clones produced interferon gamma (IFN-gamma), while 10 of 12 normals' clones did. After stimulation with calcium ionophore A23187 and phorbol myristic acetate (PMA), the production of IL-4 was markedly increased in both patients and normals. However, only 3 of the 12 patients' clones produced IFN-gamma, while all of the normals' clones did. The T-cell clones of both patients and normals produced comparable IL-2. To study the kinetics of lymphokine productions, a HLA-DRw12-restricted T-cell clone (FYD 3.1) was stimulated, respectively, with a combination of A23187 and PMA, phytohemagglutinin (PHA), or Dp antigen in the presence of APCs. Maximal IL-2 and IL-4 productions were detected 12 hr after A23187 and PMA stimulation, whereas IFN-gamma could not be detected even 36 hr after stimulation. When stimulated with PHA, the production of IFN-gamma peaked on the fourth day, but IL-4 was not detected. After stimulation with Dp antigen and APCs, IL-4 and IL-2 were detected on the second and third days, but IFN-gamma was not detected. The IgE production by autologous purified B cells in the presence of allergen or IL-4 was found to be augmented by the FYD 3.1 T-cell clones. IFN-gamma was observed to counteract the effects of the T-cell clones and IL-4. Thus, the secretory patterns of lymphokine and kinetics of lymphokine production of allergen-specific T-cell clones can be used to explore the regulatory mechanism of human IgE synthesis [corrected].

The effect of Dermatophagoides pteronyssinus allergens on proliferation and CD23 antigen expression of peripheral blood lymphocytes from atopic patients

The low affinity IgE receptor (Fc epsilon RII/CD23) has been proposed to be involved in the regulation of IgE synthesis. The present study was undertaken to investigate the responses to in vitro stimulation by allergen (Dermatophagoides pteronyssinus; D.p) and/or interleukin-4 (IL-4) of peripheral blood lymphocytes (PBLs) isolated from atopic and non-atopic subjects. IL-4 induced up to 5 fold increase in CD23 expression on PBLs from both atopic patients and normal controls, whereas the D.p extract increased CD23 expression on cells from 7 of 8 atopic donors and from 2 of 8 normal controls. The combination of IL-4 and allergen had an additive effect of CD23 expression. PBLs from 6 of 8 atopic patients but 1 of 8 normal controls showed significant proliferative responses to D.p extract whereas IL-4 did not induce any cell proliferation. The dose of D.p extract required for the maximal CD23 expression was 20 fold higher than that for cell proliferation. These results imply that allergen stimulation, presumably through proliferating allergen specific T cells which secrete IL-4, activates B cells from most atopic donors and a few non-atopic donors resulting in increased CD23 expression. This allergen-mediated CD23 expression may play an important role in specific IgE production.

Activated T cells and eosinophilia in bronchoalveolar lavages from subjects with asthma correlated with disease severity

Activated T-lymphocytes may regulate the eosinophilic inflammation of bronchial asthma. In the present study, we investigated T cell activation and eosinophilia in blood and bronchoalveolar lavage (BAL) in 17 patients with asthma not receiving steroid treatment. Compared to normal individuals, BAL from patients with asthma contained significantly increased numbers of both lymphocytes and eosinophils (EOSs). The lymphocytosis consisted of increased numbers of both CD4+ and CD8+ T cells, and these T cell populations expressed elevated levels of T cell activation markers (interleukin-2 receptor [CD25], HLA-DR, and very late activation antigen 1). Close correlation was found between numbers of BAL CD4+ IL-2R+ T cells and numbers of EOSs. Moreover, the numbers of activated T cells and EOSs were related to the severity of asthma as measured by impairment of FEV1 and increased methacholine bronchial responsiveness. We demonstrate in both blood and BAL a close correlation between T cell activation, eosinophilia, and severity of asthma, suggesting that recruitment and activation of lymphocytes and EOSs are fundamental to the pathogenesis of bronchial asthma.

HLA class II restriction specificity of Dermatophagoides spp. reactive T lymphocyte clones that support IgE synthesis

The results of recent experiments investigating the restriction specificity of cross-reactive, or Dermatophagoides farinae-specific, T cell clones isolated from an atopic individual with perennial rhinitis are reviewed. The restriction specificity was examined using serological inhibition, allogeneic presenting cells and murine fibroblasts expressing HLA-D region products. Although serological inhibition studies suggested that DR class II proteins were the major restriction elements used, the patterns of recognition observed with the allogeneic cell panel were complex, generally failing to correlate with the serologically defined MHC class II specificities. Analysis of the restriction patterns indicated that the majority of the T cell clones were restricted by DR beta III gene products and this was confirmed using murine fibroblasts expressing DRw52. DR beta I gene products functioned as restriction elements in the recognition of house dust mite allergen by the other clones. In an in-vitro model of allergen-dependent IgE synthesis, both DR beta I and DR beta III class II restricted T cells could be shown to provide functional help for IgE synthesized by autologous B cell-enriched populations.

Human IgE-binding factors

The production of IgE antibodies is known to be regulated by isotype-specific mechanisms that are not antigen specific. During the last decade several studies have indicated that soluble factors with affinity for IgE (IgE-binding factors, IgE-BFs) may exert such a role by interacting with IgE-bearing B lymphocytes. In the human, some of these IgE-BFs appear to be identical to soluble CD23, a B-cell surface marker thought to be involved in the control of B-cell proliferation or differentiation. In this article, Guy Delespesse and colleagues summarize several new findings regarding the cellular origin, structure and function of IgE-BFs/sCD23.

Inflammatory cells in bronchial asthma

A diagrammatic representation of the interactions between mediators of hypersensitivity and leukocytes in early, late-phase, and ongoing asthma is shown in Figure 1. Early phase or immediate reactions are largely the result of bronchoconstriction consequent to the release of mediators such as histamine, PGD2, LTC4/D4, and PAF. The principal mediator cell (MC) is the mast cell (although other IgE receptor-bearing cells such as the macrophage, eosinophil, and platelet might also be involved in this immediate response). The stimulus for mediator cell activation may be either immunologic (IgE-dependent) or nonimmunologic (i.e., changes in osmolarity as a result of the respiratory water loss associated with exercise-induced asthma). Late-phase reactions appear to be a consequence of infiltration with neutrophils (N), eosinophils (E), and macrophages (M phi). These cells are recruited and activated either by mast cell-associated chemotactic factors [such as LTB4, PAF, the eosinophil chemotactic factor of anaphylaxis (ECF-A), or high-molecular weight neutrophil chemotactic activity (NCA (HMW))] and/or "lymphokines" derived from T-helper cells (TH) which have been stimulated by antigen processed by the antigen-processing cells (APC). These mononuclear cell interactions are under the control of regulatory T cells [T suppressor (TS) cells] and it is speculated that the availability of these subsets may determine the magnitude of the late-phase response. Lymphokines and monokines which selectively activate neutrophils, eosinophils, and monocytes include LIF, EAF, and IFN-gamma, respectively. Macrophage-derived tumor necrosis factor (TNF) also amplifies the inflammatory response by its capacity to enhance eosinophil cytotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

IgE-binding factors: their possible role in the regulation of IgE synthesis

B cell-derived IgE-BFs (sCD23) are cleavage fragments of surface Fc epsilon R II. Their production is increased by IL4 and suppressed by IFN-gamma and IFN-alpha. IgE-BFs are likely to play a role in the regulation of human IgE synthesis as shown by the following two observations: i. MabER specifically blocks both the spontaneous IgE by synthesis by atopic B cells and the IL4-induced IgE synthesis by normal lymphocytes, ii. purified IgE-BFs enhance the IL4-induced and the spontaneous IgE synthesis. Soluble fragments of Fc epsilon R II also display BCGF-like activity although the exact structure of these fragments is not yet identified. The cDNA coding for Fc epsilon R II has been cloned and functionally expressed. The predicted amino acid sequence reveals no homology between human and rodent IgE-BFs indicating that they are unrelated molecules.