Characterization of human T cell-derived IgE-potentiating factor

Enhancement of IgE synthesis in the human myeloma cell line U-266 with an IgE binding factor from a human T-cell line

An IgE-binding factor(s) (IgE-BF(s] was partially purified from the supernatant of human HTLV-II carrying T-cell line MO. This IgE-BF(s) was shown to increase the IgE synthesis in the human myeloma cell line U-266, but did not affect its viability or growth. The effect of the IgE-BF(s) was dose-dependent and selective for IgE protein synthesis as beta 2-microglobulin synthesis in the U-266 and the immunoglobulin production in the U-1958 IgG-secreting human myeloma cell line were unaffected. The IgE-BF(s) increased the production of the epsilon heavy chain but not the lambda light chain production. The IgE-BF(s) was distinct from IL-1 beta, IL-3, IL-4, IL-5, IL-6, TNF-alpha, IFN-alpha, -beta, -gamma, M-CSF, and fragments of CD23.

Serum levels of soluble IL-2 receptor, IL-4 and IgE-binding factors in childhood allergic diseases

The serum levels of soluble IL-2 receptor (sIL-2R), IL-4 and IgE-binding factors were examined in children with allergic diseases, and compared with those in non-allergic controls of the same age and sex. The results showed age-related decreases in the serum levels of sIL-2R and IgE-binding factors, but not in that of IL-4 in both allergic and non-allergic individuals. Significant elevation of sIL-2R was observed in sera from children with atopic eczema or history of an anaphylactic reaction to food, as compared with that in non-allergic controls. The serum concentration of IL-4 was elevated in all allergic groups, including cases of atopic eczema, bronchial asthma and anaphylaxis to food, compared with non-allergic controls, and was correlated significantly with the serum level of IgE (r = 0.59). The IgE-binding factor levels in sera from patients aged 6-10 years with bronchial asthma, or patients aged 1-5 years with a history of food anaphylaxis were elevated as compared with those in non-allergic controls of same age. There was no significant correlation between the serum levels of IgE-binding factors and IgE. Since sIL-2R is released by activated T cells, the present study is in favour of T cell activation causing allergic skin disorders. The serum levels of IL-4 as well as IgE did not differ among allergic patients of different clinical categories. The role of IgE in atopic eczema and other allergic diseases is not clearly established; however, it seems likely that IL-4 is deeply involved in the increased production of IgE seen in allergic individuals. The possible involvement of IgE-binding factors in the age-related changes of clinical manifestations in childhood allergic diseases was also discussed.

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.

Regulatory effects of human IgE-binding factors in the IgE synthesis by human and rat lymphocytes

We have previously established human T cell hybridomas which produce IgE-binding factors. Incubation of one of the T cell hybridomas, 166A2, with human IgE dimer in the presence of 1 microgram/ml bradykinin resulted in the formation of IgE-binding factors having affinity for lentil lectin. The factors selectively enhanced both IgE-forming cell responses of rat mesenteric lymph node (MLN) cells and spontaneous IgE synthesis by human peripheral blood B cells of atopic patients, without affecting the IgG response. The same factors that enhanced IgE synthesis of B cells from atopic patients also enhanced IgE synthesis induced under bystander conditions by activated alloreactive T cells. Fractionation of the affinity-purified IgE-binding factors by gel filtration revealed three molecular mass species, i.e., 60 kDa, 30 kDa and 15 kDa. The 60-kDa and 15-kDa IgE-binding factors selectively enhanced both the spontaneous IgE synthesis by B cells of atopic patients and IgE response of rat MLN cells. In contrast, the 30-kDa IgE-binding factors had only marginal enhancing effects on the IgE synthesis by both human B cells and rat MLN cells. When the 166A2 hybridoma cells were incubated with IgE dimer in the presence of glycosylation-inhibiting factor (GIF), essentially all IgE-binding factors formed by the cells had affinity for peanut agglutinin (PNA) but for neither lentil lectin nor concanavalin A. All of the 60-kDa, 30-kDa and 15-kDa species, having affinity for PNA, selectively suppressed the potentiating factor-enhanced IgE response of rat MLN cells. The factors also suppressed the IgE synthesis of human B cells from atopic patients when the synthesis was enhanced by IgE-potentiating factor. The results indicate that human IgE-binding factors regulate IgE synthesis by both human and rat lymphocytes.

IgE response and its regulation in allergic diseases

The distinguishing feature of the allergic person is his or her elevation of serum IgE. This propensity to develop a sustained IgE response is determined genetically. The biologic effects of IgE are mediated via Fc receptors (Fc epsilon R) present on mast cells and basophils (Fc epsilon R type 1) and subpopulations of monocytes, macrophages, eosinophils, and platelets (Fc epsilon R type 2). Interaction of allergen with IgE on these cells results in receptor "bridging" and the release of histamine and other inflammatory mediators. Fc epsilon R type 2 on lymphocytes and monocytes are upregulated in atopic disease and may play a role in the allergic inflammatory reaction. The activation of B cells to synthesize IgE requires several stages (see Fig. 2). T cells play an important role in the regulation of IgE synthesis. In vitro activation of resting B cells to synthesize IgE requires direct cellular interaction with T cells or the presence of IL4 for activation. The latter effect is inhibited by alpha-interferon. Preactivated B cells are influenced in an isotype-specific manner by T-cell-derived IgE binding factors (IgE-BF), which may act as IgE-potentiating or IgE-suppressive factors, depending on their degree of glycosylation. The regulation of IgE synthesis is an important area of investigation. It provides us with an understanding of the basis of the human allergic response and ultimately may provide the basis for novel strategies in the treatment of allergic diseases.

Subset of natural killer cells is induced by immune complexes to display Fc receptors for IgE and IgA and demonstrates isotype regulatory function

Expression of Fc receptors for IgE (FcER) or IgA (FcAR) on purified natural killer (NK) cells was investigated. No FcER+ and a few FcAR+ NK cells were detectable on freshly separated NK (NKH-1+) cells from normal donors. Incubation of NK cells with IgE-anti-IgE immune complexes or IgA-anti-IgA immune complexes induced up to 10 and 20% FcER+ or FcAR+ cells, respectively. These FcR were induced on CD3- but not on CD3+ NKH-1+ cells. In contrast, NK cells from patients with various dysgammaglobulinemias could not be induced to express FcER or FcAR corresponding to their abnormal circulating IgE and/or IgA levels. Enriched FcER+ or FcAR+ induced NK cell supernatants from normals enhanced IgE or IgA synthesis from Ig secreting B cell lines in an isotype-specific fashion without increasing proliferation. Thus NK cells, after interaction with specific Ig isotypes in complexes, express FcR and produce differentiation factors for that isotype.

Human recombinant interleukin 4 induces normal B cells to produce soluble CD23/IgE-binding factor analogous to that spontaneously released by lymphoblastoid B cell lines

Surface-labeled Epstein-Barr virus (EBV)-transformed lymphoblastoid RPMI 8866 cells release in their supernatant a radiolabeled 25-kDa polypeptide which reacts with the Fc epsilon RL/CD23-specific monoclonal antibody (mAb) 25 and which binds to IgE but not IgG (IgE BF/sCD23). IgE BF/sCD23 had an isoelectric point of 4.5-5.0. The reactivity of mAb 25 with IgE BF/sCD23 allowed us to set up a radioimmunoassay for detection of IgE BF/sCD23 in cell culture supernatants. Supernatants from Fc epsilon RL/CD23+ cell lines were found to contain IgE BF/sCD23. Addition of human recombinant interleukin 4 (IL 4) to normal human B cells cultures induced the production of IgE BF/sCD23. Activation of B cells with anti-IgM antibody coupled to beads enhanced the IL 4-induced production of IgE BF/sCD23 when compared to nonactivated B cells. This correlates with the finding that anti-IgM antibody-activated B cells cultured with IL 4 express more Fc epsilon RL/CD23 than B cells cultured with IL 4 alone. The biochemical characteristics of radiolabeled IgE BF/sCD23 immunoprecipitated by mAb 25 from the supernatants of normal B cells cultured with IL 4 were identical to those of the IgE BF/sCD23 isolated from EBV-transformed cell line supernatants. Addition of interferon-gamma to B cells cultured with IL 4 strongly decreased the level of IgE BF/sCD23 in culture supernatants correlating with the observed decrease of Fc epsilon RL/CD23 on B cell surface. These data demonstrate that normal human B cells cultured in the presence of IL 4 produce an IgE-binding factor (sCD23) biochemically and antigenically equivalent to that spontaneously produced by EBV-transformed lymphoblastoid cell lines.