Induction of interleukin-4-dependent IgE synthesis and interleukin-5-dependent eosinophil differentiation by supernatants of a human helper T-cell clone

Haplorchis taichui: worm recovery rate and immune responses in infected rats (Rattus norvegicus)

Worm recovery rate, mucosal mast cells (MMCs), eosinophils and serum IgE concentration in rats were investigated after orally feeding 300 Haplorchis taichui metacercariae to male rats. The duodenal, jejunal and ileal tissue sections were stained with 1% alcian blue and 0.5% safranin-O for MMC count. Eosinophil count and the serum IgE concentration assay were measured from cardiac puncture blood. The average worm recovery rates were 20.00%, 13.00%, 0.67%, 1.67% and 0.00% on day 3, 7, 14, 21 and 28 post-infection (PI), respectively. The number of MMCs in the infected rats were significantly higher than in the controls (P<0.01), reaching a peak on day 21 PI. They decreased thereafter, with the decline in worm recovery. Eosinophil count and Serum IgE concentration were also increased but not significantly higher than the controls. However, they showed a positive relationship to worm recovery. It could be concluded from the results that MMCs, eosinophils and IgE may play an important role in the expulsion of H. taichui from rat intestine. However, the mechanism by which the MMC result in the helminth expulsion still need to be understood, and it is recommended that other cells such as goblet cells be studied further.

Immunological changes associated with clinical improvement of asthmatic children subjected to psychosocial intervention

In the present study we evaluated the impact of a program of psychosocial intervention (PSI) on the immunological status and the clinical management of a group of asthmatic children of an island population in Venezuela. We studied a total of 35 asthmatic children who belonged to either a PSI group (19 patients) or a control group (16 patients), both of which received conventional antiasthmatic treatment. The PSI group received, in addition, a 6-month psychosocial intervention program which included relaxation, guided imagery, and self-esteem workshops. During the PSI period, the number of asthmatic episodes and the use of bronchodilator medication were significantly reduced, and pulmonary function was significantly improved, compared to the 6 months before intervention. There was also a significant reduction in the specific IgE responses against the most important allergen in these children, the intestinal parasite Ascaris lumbricoides. PSI resulted in a significant increase of NK cells, an augmented expression of the T-cell receptor for IL-2, and a significant decrease of leukocytes with low affinity receptors for IgE. In fact, these surface markers became similar to those of nonasthmatic children from both Coche Island and the mainland. None of these clinical or immunological changes were seen in the control group of asthmatics who did not undergo PSI. These results are consistent with the possibility that PSI induces immunological alterations that are responsible for the clinical and physiological improvements observed in the study group.

The direct effect of interferon-gamma on human eosinophilic leukemia cell lines: the induction of interleukin-5 mRNA and the presence of an interferon-gamma receptor

The EoL-1 and EoL-3, human eosinophilic leukemia cell lines, have been used as models for studying the maturation and the function of human eosinophils. We investigated the effects of interferon-gamma (IFN-gamma) on superoxide anion (O2-) production of these cell lines and interleukin-5 (IL-5) mRNA expression in the EoL-1. O2- was measured by chemiluminescence of MCLA, one of cypridina luciferin analogs. The O2- production of fMLP-stimulated EoL-1 and EoL-3 was increased by the IFN-gamma treatment. IL-5 mRNA expression was detected in the IFN-gamma-treated EoL-1 by reverse transcription-polymerase chain reaction (RT-PCR). Further, we examined IFN-gamma receptor 1 mRNA expression in these cell lines and peripheral blood eosinophils by means of northern blot hybridization. IFN-gamma receptor 1 mRNA was detected in the EoL-3 and the IFN-gamma-treated EoL-1. A weak expression of IFN-gamma receptor 1 mRNA was detected in peripheral blood eosinophils isolated from a patient with eosinophilia. These results suggest that IFN-gamma may act on eosinophils directly through its receptor.

Milk-induced eczema is associated with the expansion of T cells expressing cutaneous lymphocyte antigen

The extravasation of T cells at sites of inflammation is critically dependent on the activity of homing receptors (HR) involved in endothelial cell recognition and binding. Two such HR (the cutaneous lymphocyte antigen [CLA] and L-selectin) have been shown to be selectively involved in T cell migration to skin and peripheral lymph nodes, respectively. This study was designed to assess the relationship between the organ specificity of an allergic reaction to food and the expression of HR on T cells activated in vitro by the relevant food allergen. Peripheral blood mononuclear cells were isolated from seven milk allergic children with a history of eczema when exposed to milk. All patients had a positive prick skin test and double-blind placebo-controlled food challenge to milk. 10 children with either allergic eosinophilic gastroenteritis or milk-induced enterocolitis and 8 nonatopic adults served as controls. Five-parameter flow cytometry using monoclonal antibodies was used for detection of the specific HR on freshly isolated T cells versus T cell blasts induced by a 6-d incubation with casein, as compared with Candida albicans. After in vitro stimulation with casein, but not C. albicans, patients with milk allergy and atopic dermatitis had a significantly greater percentage of CLA+ T cells (P < 0.01) than controls with milk-induced enterocolitis, allergic eosinophilic gastroenteritis, or nonatopic healthy controls. In contrast, the percentage of L-selectin-expressing T cells did not differ significantly between these groups. These data suggest that after casein stimulation allergic patients with milk-induced skin disease have an expanded population of CLA+ T cells, as compared with nonatopics or allergic patients without skin involvement. We postulate that heterogeneity in the regulation of HR expression on antigen-specific T cells may play a role in determining sites of involvement in tissue-directed allergic responses.

Th2 cytokine mRNA expression in skin in cutaneous T-cell lymphoma

We have previously demonstrated that peripheral blood mononuclear cells from patients with Sézary syndrome, the leukemic form of cutaneous T-cell lymphoma which is accompanied by erythroderma and lymphadenopathy, have a Th2 cell cytokine [interleukin 4 (IL-4) and interleukin 5] production pattern. In this study, we extend these observations to demonstrate a correlation of the presence of a Th2 cytokine pattern with a malignant T-cell clone in different stages of cutaneous involvement among patients with cutaneous T-cell lymphoma (CTCL). Skin biopsies were obtained from 12 CTCL patients with various disease stages (three patch, three plaque, six tumor), three patients with parapsoriasis, four patients with inflammatory dermatoses, including two psoriasis and two lichen planus, and 12 normal controls. Total RNA was extracted, reverse transcribed, and PCR amplified with IL-2, IL-4, IL-5, interferon gamma (IFN-gamma), and beta-actin oligonucleotide primers. Although all skin specimens tested had detectable IL-2 and IFN-gamma mRNA, only specimens from patients with CTCL or parapsoriasis had demonstrable IL-4 and/or IL-5 mRNA. Specifically, IL-5 mRNA was detected in skin biopsies from five of six tumor-stage CTCL, two of three plaque-stage CTCL, one of three patch-stage CTCL, and 1 of 3 parapsoriasis patients, whereas IL-4 mRNA was demonstrated to be present in five of six tumor-stage, one of three plaque stage, none of three patch-stage CTCL, and none of three parapsoriasis patients. These results indicate that in all stages of cutaneous involvement of CTCL, encompassing patch stage through tumor stage, IL-4 and IL-5 mRNA is variably detectable. In tumor-stage skin lesions, typically characterized by a dense dermal infiltrate of malignant T cells, Th2 cytokine mRNA is virtually always detectable. The ability to detect Th2 cytokine mRNA in the skin of patients with CTCL supports our previous findings that the malignant T cells in CTCL possess a Th2-helper cell phenotype.

Anti-CD23 monoclonal antibodies: comparisons of epitope specificities and modulating capacities for IgE binding and production

A large battery of anti-CD23 mAb were compared for their epitope specificities and for their abilities to alter both IgE binding to cell-associated CD23 and IgE production in vitro in response to three sets of stimulants. The nine mAb tested can be divided into four families which define four antigenic epitopes (A-D) of CD23. Of these four families, two bind antigenic sites, (A and D) that appear to lie outside the IgE ligand binding site and two bind sites (B and C) that appear to be located within or close to this site, as determined by the abilities of appropriate mAb to alter IgE binding to CD23. The effects that these mAb had on IgE secretion by normal peripheral blood mononuclear cells (PBMNC) varied depending on the stimulant employed to induce IgE production. Interactions with epitope A, which was found to lie outside the ligand binding site and to be made more accessible by binding of mAb to other epitopes, had different effects on IgE production than interactions with the other epitopes. Indeed, mAb binding to this epitope lead to as much as a 10 fold enhancement in IgE biosynthesis induced by IL-4 alone or by IL-4 + hydrocortisone whereas interactions at the other sites resulted in almost complete inhibition of IgE production. In addition, mAb reactive with epitopes B and C had minimal effects on IgE production induced by IL-4 + anti-CD40 mAb whereas interactions at epitope A consistently enhanced IgE production. Finally, no apparent direct correlation was found between the ability of individual anti-CD23 mAb to alter IgE binding to cell-associated CD23 and their ability to modulate IgE production by PBMNC. These studies suggest that IgE binding to cell-associated CD23 does not have a major role in the de novo synthesis of IgE that involves CD23 interactions. In addition, the different effects that binding to epitope A vs B or C have on IgE synthesis suggest that molecular interactions between distinct portions of the CD23 molecule and other cell surface molecules expressed on the same B cell or adjacent communicating cells may lead to divergent cellular effects on IgE production. Finally these studies imply that only epitope A is involved in the generation of an IgE response through the CD40 pathway.

Is asthma curable?

The information reviewed here supports the concept that asthma is potentially curable. Reports of complete, durable remission of asthma can no longer be regarded as fortuitous occurrences, unrepresentative of asthma in general. Systematic studies of anti-inflammatory drug therapy designed to explore possible induction or remission of asthma clearly are warranted. Studies of aggressive anti-inflammatory drug therapy of asthma at the onset, to avoid establishment of chronic asthma, also are desirable. The current goals of therapy of asthma have been revised to include reduction of airway hyperreactivity with topical anti-inflammatory drugs, in addition to relief of current symptoms. This approach may provide valuable resistance to exacerbations in response to antigen exposures, infections, exercise, or irritants. Pathophysiologic mechanisms apparently essential to the establishment and perpetuation of chronic asthma have been identified. These processes may be vulnerable to eradication by combination therapy with existing pharmacologic agents such as cyclosporin A or FK-506 (to suppress cytokine production), gold, methotrexate, and other anti-inflammatory drugs, alone or in combination. Equally important, the vigorous anti-inflammatory therapy may be necessary only long enough to achieve a resolution of the chronic pulmonary inflammation. Systematic studies of the use of these agents to induce partial, or complete, stable remissions of asthma should be performed. In the past, remissions of asthma in children with neoplasia and the other patients presented herein were complete, durable, and welcome, but they were largely unexpected and unpredictable. For the future, there is increasing reason to believe that predictable pharmacologically induced remission of asthma will be feasible.

The role of T cells and the effect of hydrocortisone on interleukin-4-induced IgE synthesis by non-T cells

The role of T cells for IL-4-induced IgE synthesis by peripheral blood mononuclear cells (PBMC) was investigated. The removal of monocytes from PBMC abolished IL-4-induced IgE synthesis. When PBMC were separated into T and non-T cells, non-T cells alone were not able to secrete significant amounts of IgE in the presence of IL-4. Depending on the separation procedure, the reconstitution of non-T cells with T cells prepared by rosetting did not restore IgE secretion, whereas T cells obtained by the use of anti-CD3 antibodies could co-induce IgE formation. However, when the T cells were first irradiated, large amounts of IgE were produced, which strongly exceeded those found in unseparated PBMC cultures. IL-4-induced IgE synthesis was also obtained in co-cultures of formaldehyde-fixed T cells with non-T cells. Furthermore, not only autologous but also allogeneic T cells, which have been irradiated or fixed, could provide the costimulatory effect on IgE formation by non-T cells in the presence of IL-4. Mitogenically pre-activated T cells, however, were not able to support IgE synthesis. Hydrocortisone (HC) potentiated the IL-4-induced IgE synthesis by PBMC and enabled non-T cells to secrete IgE in the presence of IL-4. Adding both HC and T cells led to a marked synergistic effect on IL-4-induced IgE production. We conclude that monocytes are required for the induction of IgE synthesis in PBMC in addition to T cells and IL-4. Our results support the view that the T cell signal is delivered via cognate and non-cognate T/B cell membrane interaction. Furthermore, active and proliferating T cells rather suppress IgE synthesis. Finally, HC appears to be a potent alternative stimulus, which bypasses the necessity for T cells in IL-4-induced IgE formation.

Reciprocal regulatory effects of IL-4 on cell growth and immunoglobulin production in Ig-secreting human B-cell lines

The effects of interleukin-4 (IL-4) on cell proliferation and immunoglobulin (Ig) production from three different Ig-secreting B-cell lines (U266, IgE; HSCE-, IgG; LA 350, IgM) were analyzed. Addition of IL-4 increased Ig production by the IgE- and IgG-secreting cell lines and this was paralleled by an inhibition of cellular proliferation. In contrast, the addition of IL-4 to LA 350 cells stimulated cellular proliferation but a decrease in IgM secretion. With each cell line, the IL-4 effects were both dose- and time-dependent and effects were maximal in the presence of 400 U/ml. Further analysis of the mechanism of IL-4 action on Ig production at the single B-cell level using an ELISA spot assay revealed a dualistic effect: increased Ig levels in culture supernatants reflected both an enhancement of single-cell Ig production as well as an increase in numbers of Ig-secreting B cells (IgE and IgG). In LA 350 cells the number of IgM-secreting B cells was suppressed as well as the amount of Ig released by single cells. These data on Ig production were supported by determination of mRNA amounts for the epsilon, gamma, and mu gene transcripts. Addition of IL-4 enhanced the levels of epsilon and gamma message in U266 and HSCE- cells, respectively, and reduced the amount of mu mRNA in LA 350 cells. In the IgE- and IgG-secreting cell lines, the IL-4 effect also correlated with enhanced expression of IL-4 receptor (IL-4R) mRNA levels, whereas IL-4R mRNA levels were unchanged in IgM-producing cells after IL-4 treatment. Incubation of cells with IL-4 and interferon-gamma abolished the stimulatory activities of IL-4 on either cell proliferation (LA 350 cells) or Ig production (HSCE- and U266); but did not influence the inhibitory activities of IL-4 on the cell lines. The immunosuppressive drug cyclosporin A (CsA) inhibited both cell proliferation and Ig production in all three cell lines to a similar degree. Furthermore, in U266 and HSCE- cells, CsA inhibition could not be overcome by IL-4. These data support the conclusion that on Ig-secreting human B-cell lines, IL-4 regulates cell proliferation and Ig production in a reciprocal fashion.

Thymopentin treatment in severe atopic dermatitis--clinical and immunological evaluations

An open clinical trial of thymopentin was conducted on 16 children with severe atopic dermatitis. The patients were treated with injections three times a week of 50 mg thymopentin for six weeks. They were then divided randomly into two groups: group A continued thymopentin for an additional six weeks, and group B were treated with normal saline. Clinical parameters and immunological function were evaluated serially. The total severity score started to decline from baseline significantly three weeks after treatment, and continued throughout the study period in group A but began to flare up in group B two weeks after stopping thymopentin. All the eight patients in group A completed the trial but three out of eight in group B dropped out because of flaring up of skin lesion. In vitro production of interleukin-4 tended to decrease and that of interferon gamma tended to increase, but total serum IgE, in vitro IgE synthesis, and abnormally low CD8+ CD11b+ suppressor T cells remained unchanged. Histamine releasing factor (HRF), plasma histamine, and respiratory burst activities of polymorphonuclear leucocytes were appreciably decreased after thymopentin treatment. It is concluded that the clinical efficacy of short term thymopentin treatment very possibly results from the decreased production of HRF and decreased release of polymorphonuclear leucocyte derived inflammatory mediators and may have no relation with antigen-IgE immune reaction.

Decreased interferon gamma and increased interleukin-4 production in atopic dermatitis promotes IgE synthesis

The mechanism(s) responsible for increased IgE synthesis in atopic dermatitis (AD) are unknown, but they may be related to either decreased interferon gamma (IFN-gamma) and/or increased interleukin (IL)-4 production. In this study we examined peripheral blood mononuclear cells (PBMCs) from 21 patients with AD, six patients with psoriasis, and 22 nonatopic healthy controls for IFN-gamma and IL-4 production after stimulation with concanavalin A (Con A). The Con A-induced proliferative response of AD PBMCs was similar to the response of healthy controls (p = 0.9). After mitogen stimulation, however, AD culture supernatants contained significantly less IFN-gamma (p = 0.001) but increased IL-4 (p = 0.001) compared with supernatants from nonatopic controls. In contrast, PBMCs from patients with psoriasis produced normal levels of IFN-gamma and IL-4 in vitro. Since IL-4 is known to decrease IFN-gamma synthesis, we examined the effect of neutralizing anti-IL-4 on IFN-gamma production. Anti-IL-4 significantly increased IFN-gamma production in patients with AD (p = 0.008) and nonatopic controls (p = 0.02) but did not normalize IFN-gamma production by AD PBMCs. Supernatants from AD PBMCs, but not supernatants from nonatopic PBMCs, induced IgE synthesis in PBMCs from nonatopic donors (p = 0.02). When an anti-IFN-gamma receptor antibody, which blocks cellular binding of IFN-gamma, was added to supernatants from nonatopic controls their capacity to induce IgE synthesis was significantly greater (p = 0.03). These results demonstrate an imbalance of IL-4 and IFN-gamma production, which may contribute to increased IgE synthesis in AD.

IL-4 and transforming growth factor-beta suppress human immunoglobulin secretion in vitro by surface IgD- B cells

The effect of IL-4 and transforming growth factor-beta (TGF-beta) on immunoglobulin secretion in vitro by peripheral blood mononuclear cells (PBMC) or purified B cells activated with murine EL4 thymoma cells and phorbol myristate acetate (PMA) was investigated. As previously reported, IL-4 induced IgE and IgG4 secretion by B cells in PBMC preparations and B cells activated with EL4 cells and PMA. However, when B cells, either in PBMC preparations or purified and activated with EL4 cells and PMA, spontaneously secreted large quantities of immunoglobulin, IL-4 suppressed the immunoglobulin secretion of all isotypes. IL-4 also suppressed the IgE secretion by B cells from an atopic dermatitis patient. This suppressive effect was not reversed by adding IL-2 or interferon-gamma (IFN-gamma) to the cultures. We also showed that TGF-beta suppressed the immunoglobulin secretion by purified B cells activated by EL4 cells and PMA. To investigate whether IL-4 or TGF-beta suppressed immunoglobulin secretion by in vivo 'switched' and isotype-committed B cells, sIgD- B cells were isolated, activated with EL4 cells and PMA and cultured with IL-4 or TGF-beta. Such activated B cells secreted large quantities of IgG1, IgG2, IgG3, IgA1, IgA2 and IgM, and IL-4 and TGF-beta suppressed all these isotypes by greater than 80%. The data demonstrated that IL-4 and TGF-beta suppress immunoglobulin secretion in vitro by in vivo isotype-committed sIgD- B cells, suggesting that these lymphokines may play a down-regulatory role on differentiated isotype-committed B cells in an isotype-unrestricted manner. The data also showed that IL-4 and TGF-beta acted directly on isolated B cells.

Cytokine regulation of immunoglobulin secretion by neonatal lymphocytes

In contrast to adult lymphocytes, neonatal lymphocytes secrete minimal amounts of Ig in response to stimulation with immobilized MAb to CD3. This deficiency could be overcome by the addition of supplemental IL-2, IL-4, or IL-6, resulting in the secretion of all Ig isotypes. There were no major differences in the distribution of Ig isotypes secreted in response to the cytokines alone or in combination. The Ig secreted in response to IL-4 or IL-6 was inhibited by MAb to CD25, suggesting that the effects of IL-4 and IL-6 were dependent on IL-2. Stimulation of neonatal lymphocytes with anti-CD3 was sufficient to induce expression of IL-2 receptors (CD25) on both T and B cells. IL-4 exerted direct effects on neonatal T cells by increasing IL-2 production and promoting IL-6 production by anti-CD3-stimulated neonatal lymphocytes. Antibody to IL-4 or IL-6 did not inhibit Ig secretion in response to IL-2 and antibody to IL-6 did not consistently inhibit Ig secretion in response to IL-4. Finally, in the presence of cyclosporin, anti-CD3-stimulated neonatal lymphocytes secreted Ig only with the combination of IL-2 and IL-4. These results have delineated unique, but not Ig isotype-specific, effects of cytokines in supporting Ig secretion by anti-CD3-stimulated neonatal lymphocytes. Deficient production of these cytokines is likely to contribute to the decreased capacity of neonatal lymphocytes to generate an Ig response.

Preparation and characterization of human interleukin-5 expressed in recombinant Escherichia coli

The gene coding for human interleukin-5 was synthesized and expressed in Escherichia coli under control of a heat-inducible promoter. High-level expression, 10-15% of total cellular protein, was achieved in E. coli. The protein was produced in an insoluble state. A simple extraction, renaturation and purification scheme is described. The recombinant protein was found to be a homodimer, similar to the natural murine-derived protein. Despite the lack of glycosylation, high specific activities were obtained in three 'in vitro' biological assays. Physical characterization of the protein showed it to be mostly alpha-helical, supporting the hypothesis that a conformational similarity exists among certain cytokines.

Regulation of immunoglobulin (Ig)E synthesis in the hyper-IgE syndrome

The hyper-IgE (HIE) syndrome is characterized by high IgE serum levels, chronic dermatitis, and recurrent infections. The mechanisms responsible for hyperproduction of IgE in HIE patients are presently unknown. We investigated whether spontaneous in vitro IgE synthesis by PBMC from seven HIE patients was sensitive to signals (cell adhesion, T/B cell cognate interaction and lymphokines: IL-4, IL-6, and IFN-gamma) known to regulate IgE induction in normals. Our results show that, unlike IL-4 dependent IgE synthesis induced in normals, spontaneous IgE production by PBMC from HIE patients was not blocked by monoclonal antibodies to CD2, CD4, CD3, and MHC class II antigens. Furthermore, antibodies to IL-4 and IL-6 did not significantly suppress IgE production. IFN-gamma had no significant effects on spontaneous in vitro IgE synthesis. To test whether an imbalance in lymphokine production might underlie hyperproduction of IgE in HIE patients, mitogen-induced secretion of IL-4 and IFN-gamma by PBMC was assessed. No significant difference was detected between HIE patients and normal controls. Thus, ongoing IgE synthesis in the HIE syndrome is largely independent of cell-cell interactions and endogenous lymphokines, and is due to a terminally differentiated B cell population, no longer sensitive to regulatory signals.

Thymopentin therapy reduces the clinical severity of atopic dermatitis

One hundred patients with moderate to severe atopic dermatitis were entered into a two-center, double-blind trial. Patients were randomized to receive either thymopentin (Timunox, n = 48) or placebo (n = 52), administered as daily subcutaneous injections for 6 weeks. Clinical extent of disease and severity parameters were measured at baseline and at regular time intervals during the study. Both the placebo- and thymopentin-treated groups demonstrated a progressive and statistically significant (p less than 0.001) decline in the overall severity of their disease, but reduction in the clinical severity score was higher in the thymopentin-treated group and statistically significant (p = 0.04) in comparison with the placebo-treated group after 6 weeks of treatment. Of the individual symptoms comprising the total severity score, pruritus (p = 0.02) and erythema (p = 0.04) were reduced significantly when thymopentin therapy was compared to placebo therapy. In addition, both the extent of body involvement and severity index (a combined severity/extent index) were significantly reduced after 6 weeks in the thymopentin-treated group in comparison to the placebo-treated group (p = 0.04). There were no serious adverse experiences in either treatment group. We conclude that treatment with thymopentin is safe and offers significant therapeutic promise for atopic dermatitis.

Recombinant gamma interferon in treatment of patients with atopic dermatitis and elevated IgE levels

PURPOSE

Recombinant gamma interferon (rIFN-gamma) inhibits IgE synthesis in vitro by human peripheral blood mononuclear cells (PBMC). These data suggest a role for rIFN-gamma in the treatment of patients with severe atopic dermatitis (AD) and elevated IgE levels. The purpose of this study was to determine the effect of rIFN-gamma treatment on IgE production in patients with AD.

PATIENTS AND METHODS

Twenty-two patients with chronic severe AD were treated with rIFN-gamma. In part I of the study, 14 patients were treated with daily subcutaneous injections at three successive dose levels (0.01 mg/m2, 0.05 mg/m2, and 0.1 mg/m2) for 5 days with 2 days off between each dose level. In part II, eight patients received rIFN-gamma at 0.05 mg/m2, daily for 6 weeks. One patient from part I and eight patients from part II of the study received three times per week maintenance thereby for up to 14 months. Prior to and at selected times during and after treatment, the clinical and immunologic status of the patients was assessed.

RESULTS

In part I, spontaneous de novo IgE synthesis by PBMC was inhibited in 10 patients receiving rIFN-gamma at 0.01 mg/m2 (p = 0.038) and in nine at 0.1 mg/m2 (p = 0.066). There was no reduction of serum IgE levels at any of the three dose levels. Total clinical severity showed improvement at each dose level (p less than 0.04) with worsening 3 days after discontinuation of treatment. In part II, there was no significant inhibition of spontaneous IgE synthesis by PBMC nor was there any reduction of serum IgE. Nevertheless, there was a progressive and significant reduction (p less than 0.01) in total clinical severity over the 6 weeks of daily rIFN-gamma with a sustained improvement during maintenance therapy.

CONCLUSION

The results of this pilot study suggest that rIFN-gamma may be efficacious in the treatment of AD and that further clinical trials are warranted.

T- and B-cell dysregulation of IgE synthesis in cystic fibrosis patients with allergic bronchopulmonary aspergillosis

Since Aspergillus fumigatus (Af)-specific and polyclonal serum IgE levels are characteristically elevated in patients with allergic bronchopulmonary aspergillosis (ABPA), we evaluated in vitro regulation of IgE synthesis in cystic fibrosis (CF) patients with ABPA. We studied 11 CF patients with ABPA, 37 patients with positive Af prick skin tests and/or IgG precipitating antibodies (ST/PPT+), and 35 patients with no humoral or skin responses to Aspergillus (ST/PPT-). Mean serum IgE concentration was significantly elevated in CF subjects with ABPA compared to ST/PPT+ and ST/PPT- patients, 2866 vs 303 and 61 IU/ml, respectively (P less than 0.01). In vitro studies demonstrated that ABPA patients' B cells spontaneously synthesized significantly increased amounts of IgE compared to ST/PPT positive and negative subjects, 1980 vs 220 and 13 pg/ml, respectively (P less than 0.01). In addition, preformed B-cell-associated IgE was also significantly elevated in ABPA subjects (P less than 0.01), indicating prior in vivo activation. Supernatant cultures of Af-stimulated T cells from ABPA subjects significantly induced allogeneic B-cell IgE synthesis compared to ST/PPT positive and negative CF subjects, 206 vs 13 and 4 pg/ml, respectively (P less than 0.01). Thus T cells stimulated with Aspergillus antigens secrete cytokines that induce B-cell IgE synthesis in ABPA subjects. B-cell IgE hyperactivity is manifested by in vivo and in vitro increased IgE concentrations. Analyses of T-cell regulation and B-cell IgE synthesis distinguish CF subjects with ABPA from Aspergillus sensitive non-ABPA subjects.

In vitro and in vivo studies with purified recombinant human interleukin 5

The functional activities of highly purified recombinant human IL 5 (hIL 5) have been characterized on a number of cell types in vitro and in BALB/c mice in vivo. In vitro, hIL 5 could induce the differentiation of eosinophils from precursors in both human and mouse bone marrow with approximately the same efficiency. A mouse IL 5/3-dependent B cell line, LyH7.B13, was found to proliferate in response to hIL 5 but not human interleukin 1 (IL 1), interleukin 2 (IL 2), interleukin 3 (IL 3), interleukin 4 (IL 4), interleukin 6 (IL 6), interferon-gamma (IFN-gamma), or granulocyte macrophage-colony stimulating factor (GM-CSF) and was at least 10-fold more sensitive than BCL1 mouse lymphoma cells. We have successfully used this cell line to demonstrate the production of IL 5 by human T cell clones. In marked contrast to its effects on murine B cell lines, hIL 5 had no demonstrable activity on CD23 expression, anti-mu costimulated proliferation or IgM, IgG, or IgE production by tonsillar B cells and did not influence such responses triggered by IL 4. BALB/c mice injected with hIL 5 for 7 consecutive days were shown to develop an eosinophilia comparable to that induced by infection with the parasite Mesocestoid corti.

Interleukin-4 induces both IgG4 and IgE secretion by peripheral blood B cells

Peripheral blood mononuclear cells (PBMCs) from healthy nonallergic donors were cultured with recombinant interleukin-4 (rIL-4), and the Ig of different isotypes was quantitated in the culture supernatants by radioimmunoassays. Recombinant IL-4 induced IgG4 and IgE secretion in a dose-dependent manner, whereas it had no consistent effect on the secretion of the other isotypes. In the absence of rIL-4, B cells in the PBMC preparations secreted less than 1 ng IgE/ml and a mean of 5 ng IgG4/ml. In the presence of the optimal dose of 100 U rIL-4/ml, PBMCs from five donors secreted a mean +/- SEM of 37 +/- 8 ng IgE/ml and 66 +/- 25 ng IgG4/ml. In kinetic studies, no IgG4 or IgE secretion was detected during the first 5 days of culture, and approximately 50% of the IgG4 and IgE secreted by day 15 was detected in supernatants on day 7. Cycloheximide, actinomycin-D, and mytomycin-C completely inhibited the rIL-4-induced IgG4 and IgE secretion, indicating that de novo protein, RNA, and DNA synthesis was required. As shown by Percoll buoyant density centrifugation, rIL-4 induced B cells in the high-density fraction to secrete IgG4 and IgE, whereas it inhibited spontaneous IgG4 secretion by low-density B cells. Interferon-gamma inhibited IL-4-induced IgG4 and IgE secretion. The data demonstrate that IL-4 induces small, dense, peripheral blood B cells to secrete not only IgE but also IgG4, which parallells the IL-4-induced IgE and IgG1 secretion by murine B cells.(ABSTRACT TRUNCATED AT 250 WORDS)

The control of antibody production by immunomodulatory molecules

Regulation of human B cell responses is a complex process that involves the activities of a variety of cytokines. There are important differences between the regulation of human and murine B lymphocytes, especially with regard to the action of IL-2. In humans, IL-2 appears to play a central role in regulating B cell activation, proliferation, and differentiation, thereby facilitating the production of immunoglobulins of all isotypes. A wide array of additional cytokines can amplify antibody production, but none appears to be able to do this in the absence of IL-2; moreover, none appears to enhance the production of only a single isotype of immunoglobulin. Beyond the positive influences of cytokines on B cell responses, at least 2 cytokines, IL-4 and TGF beta, suppress B cell proliferation and differentiation. Inhibition by each of these cytokines can be overcome by specific cytokines that provide positive signals to B cells. Antibody production is thus regulated by a complex array of cytokines with complementary or opposing effects that may be exerted at different stages of B cell responsiveness. Whether specific subpopulations of B cells exhibit unique cytokine requirements for differentiation has not been clearly delineated, nor is it clear whether autoantibody production is uniquely regulated by cytokines. Additional information concerning the role of cytokines in the regulation of B cell function should provide further insight not only into normal antibody production, but also into potential dysregulation that leads to autoimmunity.

Endogenous interleukin 6 plays an obligatory role in interleukin 4-dependent human IgE synthesis

The lymphokine interleukin (IL) 4 plays a crucial role in the regulation of IgE synthesis. In the present study, the cellular and cytokine requirements for the IL4-dependent induction of IgE synthesis in humans were analyzed. Recombinant IL4 could induce IgE synthesis by peripheral blood mononuclear cells and autologous T/B cell mixtures, but not by highly purified B cells. IgE induction by IL4 was strongly decreased in monocyte-depleted peripheral blood mononuclear cells. These results show that the induction of IgE synthesis by recombinant IL4 is T cell dependent and optimal in the presence of monocytes. IL5 and IL6, but not IL2, IL1 and tumor necrosis factor-alpha, strongly up-regulated the IL4-dependent synthesis of IgE, with modest effects on cell proliferation. An anti-IL6 polyclonal antibody strongly inhibited IL4-driven IgE production. Endogenous IL6 plays, therefore, an obligatory role in the IL4-dependent induction of IgE. However, a combination of IL4, IL5 and IL6 (with or without IL1) at optimal concentrations could not induce IgE synthesis by purified normal B cells, indicating that cytokine-mediated signals, although essential, are not sufficient for the IL4-dependent induction of IgE synthesis.

Induction of human IgE synthesis requires interleukin 4 and T/B cell interactions involving the T cell receptor/CD3 complex and MHC class II antigens

The induction of IgE synthesis by IL-4 requires T cells and monocytes, as well as T cell- and monocyte-derived cytokines. Optimal cytokine combinations, however, fail to induce highly purified B cells to secrete IgE, indicating that additional signals are required. We show herein that the induction of human IgE synthesis by rIL-4 requires cognate interaction between the T cell receptor/CD3 complex on T cells and MHC class II antigens on B cells: mAbs directed against these molecules completely blocked IL-4-dependent IgE induction. mAbs against cell adhesion molecules (CD2, CD4, LFA-1) also inhibited IgE synthesis induced by IL-4, confirming that cell-cell contact is necessary for IgE induction. The requirement for cognate T/B cell interaction was further shown by comparing the IgE-inducing ability of two human IL-4-producing alloreactive T cell clones: F6, which recognizes MHC class II antigens on both B cells and monocytes, and A1, which recognizes an HLA-DP-associated epitope expressed on monocytes, but not on B cells. When incubated with B cells and monocytes from a normal donor bearing the appropriate alloantigen, clone F6, but not clone A1, induced vigorous IgE synthesis, although both clones proliferated and secreted IL-4. Taken together, our results suggest that at least two, possibly synergizing, signals are required for the T cell-dependent induction of IgE synthesis by B cells: one signal is delivered by cognate T/B cell interaction, the other by T cell-derived IL-4.

Regulation of human IgE synthesis

Allergic diseases result from the interaction with IgE bound to cell surface receptors. Therefore, rational therapeutic approaches to allergic diseases would be aimed at decreasing IgE and/or at blocking the binding of IgE to effector cells such as mast cells and monocytes. Our investigation of the mechanism of IgE synthesis in man shows that IgE synthesis by peripheral blood mononuclear cells (PBMC) absolutely requires the presence of IL-4 and requires endogenous IL-6, because antibody to IL-6 inhibits IgE production completely. IgE synthesis requires T/B cell contact and involves interactions between B cell surface MHC Class II molecules and T cell surface receptors, as antibodies to both of these cell surface molecules inhibit IgE synthesis. Furthermore, alloreactive T cell clones which are unable to engage the B cell MHC Class II molecules fail to induce IgE synthesis in spite of their ability to secrete IL-4. Studies on the immunoglobulin sites that are involved in IgE binding to high affinity receptors on mast cells and basophils have used recombinant fragments of IgE to block mast cell binding. These studies suggest that a stretch of 76 amino acids which straddles the C epsilon 2 and C epsilon 3 domains is essential for this binding. Parallel studies on IgE binding to low affinity receptors on monocytes and B cells suggest that sequences within C epsilon 3 are involved in this binding. Peptides or analogues that inhibit IgE binding to its cellular receptors may be useful in the treatment of allergic diseases.