Induction of high titers of anti-IgE by immunization of inbred mice with syngeneic IgE

The anti-IgE/anti-FcepsilonRIalpha autoantibody network in allergic and autoimmune diseases

Basophil granulocytes and tissue mast cells and their mediators play a role in the pathogenesis of several immune and inflammatory disorders. Human basophils and mast cells (FcepsilonRI+ cells) can be activated through immunological interaction with the IgE-FcepsilonRI network. FcepsilonRI+ cells can be triggered by cross-linking between the Fab portions of IgE and multivalent antigens (direct anaphylaxis). 'Reverse type' anaphylaxis can occur through three distinct mechanisms: antibodies against the Fcepsilon portion of IgE (anti-IgE), antibodies against epitopes of the alpha chain of FcepsilonRI (anti-FcepsilonRIalpha) and anti-IgG acting on IgG-IgE complexes bound to FcepsilonRI. Anti-IgE autoantibodies are occasionally present even in normal donors and more frequently in a variety of allergic (chronic urticaria, atopic dermatitis and bronchial asthma) and autoimmune disorders (rheumatoid arthritis, lupus erythematosus and systemic sclerosis). IgG anti-IgE from a small percentage of patients induces the release of mediators from human FcepsilonRI+ cells. Some of the anti-IgE autoantibodies present in allergic patients are non-anaphylactogenic, thus representing a possible protective mechanism preventing the association of IgE with FcepsilonRI. Anti-FcepsilonRIalpha autoantibodies also occur in a significant percentage of patients of chronic urticaria and probably non-allergic asthma and some autoimmune diseases. Although anti-IgE and anti-FcepsilonRIalpha autoantibodies, present in a percentage of patients with immune disorders, are relevant to the pathogenesis of these conditions, much remains to be learnt about their immunochemistry, their prevalence and precise role in various inflammatory diseases.

Human T cell IgD receptors react with O-glycans on both human IgD and IgA1

Previous studies on murine T cell IgD-R have shown that these receptors recognize N-glycans of murine IgD, and not of other Ig isotypes. We have now studied the specificity of IgD-R on human T cells. Human IgD digested with proteinase K to fragments of < 5 kDa inhibit the ability of T cells to form rosettes with IgD-coated ox erythrocytes. The same amount of digested IgG does not. We tested all the human Ig isotypes: IgG1, -2, -3, -4, IgA2, IgE and IgM fail to inhibit significantly at 20 microg/assay. However, IgA1 is as effective as IgD itself, showing approximately 60 % and 80 % inhibition at 5 microg and 10 microg/assay. Human IgA1 and IgD both contain Gal-1 --> 3-GalNac-rich O-linked glycans, and on this basis are both bound to ricin and jacalin. The O-linked glycans may therefore also represent the common moiety binding to IgD-R. Disaccharides Gal-1 --> 3-GalNac, and Gal-1 --> 4-Glc at 10 microg/assay blocked IgD rosetting while Gal-1 --> 6-Glc did not. We conclude that the human IgD-R is a lectin, differing from the murine IgD-R in that it has both IgA1 and IgD as ligands.

The effect of aging on the immune response: influence of phosphatidylcholine-containing lipid on IgD-receptor expression and antibody formation

It was reported previously that IgD-receptors (IgD-R) are expressed on both CD4+ and CD8+ human T cells and CD4+ murine T cells after exposure to oligomeric IgD, certain cytokines, or various pharmacological agents, as shown by rosetting with IgD-coated erythrocytes. Enhancement of antibody production is observed in mice after injection of oligomeric IgD and is mediated by these IgD-R+ T cells, while injection of monomeric IgD inhibits both IgD-R upregulation and augmentation of antibody responses induced by simultaneously injected oligomeric IgD. The effects of oligomeric IgD on IgD-R upregulation are lacking in aged mice. However, the oligomeric IgD induced enhanced antibody production can be transferred to aged mice with IgD-R+ T cells from young donors suggesting that the environment of the aged mouse supports the effector function of IgD-R+ T cells. We now report, in addition, that exposure to phosphatidylcholine (PC) and a PC-containing lipid mixture, AL721, is effective in causing IgD-R upregulation on T cells from both young and aged mice, and young humans. This effect can also be demonstrated in mice in vivo after administration of AL721. Moreover, this agent causes a two-fold enhancement of antibody production, as measured by PFC/spleen, to 4-hydroxy-5-iodo-3-nitrophenyl(acetyl)-Brucella abortus (NIP-BA) and NIP-horse red blood cells (RBC) in young and aged mice. There is no difference in the baseline membrane fluidity of lymphocytes from aged and young mice. Although PC causes an increase in membrane fluidity of lymphocytes from both young and old mice, and from humans, this effect on fluidity is not prevented by a protein kinase inhibitor, while PC's effect on IgD-R upregulation is prevented by the inhibitor. Moreover, no correlation was observed between IgD-R upregulation and membrane fluidity changes induced by AL721 administered in vivo. To evaluate the role of IgD-R induction in the augmentation of antibody production by phospholipids, the effect of monomeric IgD was investigated. The augmenting effect of AL721 on antibody production was prevented by a single injection of monomeric IgD at the time of antigen administration. We conclude that (1) PC-containing lipid mixtures are effective in enhancing antibody production in aged mice, (2) induction of IgD-R is responsible for the augmenting effects of AL721 on antibody production, and (3) monomeric IgD not only blocks the upregulation of IgD-R, as shown previously, but also the augmenting effect of previously upregulated IgD-R on T cells by preventing their interaction with surface IgD+ B cells.

IgD-receptor up-regulation on human peripheral blood T cells in response to IgD in vitro or antigen in vivo correlates with the antibody response to influenza vaccination

Aged individuals (more than 65 years) were classified as antibody (Ab) responders on the basis that they showed increases to more than or = 1:40 in serum Ab titers to all influenza virus strains present in the trivalent influenza vaccine within 4 weeks after immunization. The peripheral blood mononuclear cells (PBMC) from pre-immunization samples of blood taken from seven Ab-responders and seven Ab-nonresponders were examined for their ability to exhibit up-regulation of IgD-receptor (IgD-R) after exposure for 2 h to immobilized cross-linked IgD, as shown by rosetting with IgD-coated ox erythrocytes. The responsiveness to IgD was found to be predictive of the ability to produce Ab responses to viral protein Ag: the IgD-R up-regulation was greater than 5% in all Ab-responders and less than 4% in all the Ab-nonresponders. In addition, there was an excellent correlation between mean Ab titers (to the three viruses in sera collected 4 weeks after immunization) and the percentage of IgD-R+ cells obtained in response to IgD in PBMC from the same individual prior to immunization: p = 0.894. Injection of influenza vaccine itself also induced IgD-R on PBMC in vivo. The percentage of IgD-R+ cells peaked after 24 h, was still detectable above background by day 7 or 14, and returned to pre-injection levels by day 28 in young subjects and aged Ab-responders, but not in Ab-nonresponders. Similarly, purified peripheral blood T cells obtained from aged Ab-responders exhibited IgD-R upon immunization in vivo. These findings suggest that Ag injection causes rapid up-regulation of IgD-R by cross-linking IgD in humans as well as in mice as shown previously. In analogy with results in mice, the present data are consistent with a role for IgD-R+ T cells in the humoral response in man. Proliferative responses to influenza proteins in peripheral blood T cells from vaccinated individuals were found to peak on day 7 and were higher in Ab-responders than in Ab-nonresponders.

Is vaccination against IgE possible?

A substantial reduction in the levels of both total and antigen specific IgE will most likely result in improved symptom scores in atopic individuals. Based on this assumption we initiated a project to study the possibility of reducing levels of circulating and mast cell bound IgE, by inducing a strong autoimmune antibody response against IgE in the host. Bacterially produced fusion proteins containing constant domains two (CH2) and three (CH3) of rat IgE directly linked to the glutathione-S-transferase (GST) protein from Schistosoma japonicum or to the maltose binding protein of Esherichia coli were used as the active components of the allergy vaccine. Injection of either of these fusion proteins together with adjuvant led to the induction of a strong autoimmune anti-IgE response in several IgE low or medium responder strains of rats. Vaccination of ovalbumin sensitised Wistar rats with the GST-C2C3 fusion protein resulted in a profound decrease in serum IgE levels and later in a nearly complete block in histamine release from mast cells and basophils upon challenge with either a cross-linking polyclonal anti-IgE antiserum or a specific allergen. This shows that it is possible to reduce IgE levels in an animal to such an extent that it gives a clear clinical effect. Recent studies with an extended panel of rat strains including four IgE high responder strains, indicate that induction of the autoimmune response is dependent on the plasma concentration of IgE before vaccination. A high concentration of IgE has a negative effect on the induction of autoimmunity, most likely by inducing a B-cell tolerance in the host. Vaccinated subjects with very high IgE concentrations thereby responds poorly to the vaccine. Current studies are aimed at overcoming this potential limitation of the vaccination procedure.

Administration of an anti-IgE antibody inhibits CD23 expression and IgE production in vivo

High IgE responder BDF1 mice were immunized intraperitoneally (i.p.) with dinitrophenol4 (DNP4)-ovalbumin (OVA) in alum concomitant with intravenous (i.v.) administration of an anti-IgE monoclonal antibody (mAb). IgE levels were undetectable in mice treated with the anti-IgE antibody, whereas mice treated with isotype-matched irrelevant mAb had IgE levels comparable to that of untreated, immunized mice. Subsequent antigen challenges with DNP4-OVA, either at weekly or monthly intervals, failed to evoke an IgE response for greater than 2 months in mice treated with anti-IgE during the primary sensitization, even though the terminal half-life of the anti-IgE antibody was 7 days. This inhibition was specific for DNP4-OVA since the DNP4-OVA-suppressed mice were able to respond to keyhole limpet haemocyanin (KLH). To investigate the effects of antibody treatment at the cellular level, passive transfer experiments were performed. The primary DNP-specific IgE response of adoptive transfer recipient mice was the same whether the donor cells were from mice treated with IgG or anti-IgE. Transfer of enriched T- or B-cell populations indicated that T-cell help was not compromised by administration of the anti-IgE mAb. However, splenocytes from the anti-IgE-treated mice failed to synthesize IgE in vitro, and flow cytometric analysis of B cells from anti-IgE-treated mice showed a dose-dependent decrease in CD23+ cells following antibody treatment, which correlated with decreased serum IgE levels. Taken together, the results of these studies suggest that anti-IgE treatment suppresses IgE responses via effects on B cells rather than T cells, possibly through effects on CD23-dependent pathways.

Role of antibody and T cells in the long-term inhibition of IgE synthesis

We have shown that the long-term inhibition of IgE synthesis associated with perinatal inoculation of syngeneic IgE is accompanied by the synthesis of autoantibodies to IgE. Synthesis of IgE can also be inhibited by passive transfer of syngeneic anti-IgE antibodies. In the present investigation we made use of adoptive transfer experiments to assess the relative roles of antibodies and T cells in the inhibitory process. It was found that spleen cells from IgE-suppressed mice (synthesizing anti-IgE antibodies) could adoptively transfer the state of inhibition to syngeneic adult mice. The inhibition occurred only under conditions in which the recipient mice synthesized anti-IgE antibodies. Separated B cells, CD4+ T cells, CD8+ T cells, or a mixture of B and CD8+ T cells were ineffective. However, strong inhibition of IgE synthesis (as indicated by serum levels and numbers of IgE-secreting cells in the spleen) was observed after transfer of a mixture of B cells and CD4+ (helper) T cells. The results indicate that in this experimental model anti-IgE antibodies are the suppressive agent and that T cells do not play a role other than that of providing help to B cells for anti-IgE synthesis.

Halothane hepatitis patients have serum antibodies that react with protein disulfide isomerase

Clinical and laboratory evidence suggests that the fulminant liver failure sometimes associated with the inhalation anesthetic halothane may be an immune-mediated toxicity. Most importantly, the vast majority of patients with a clinical diagnosis of halothane hepatitis have serum antibodies, which react with one or more specific liver microsomal proteins that have been covalently altered by the trifluoroacetyl chloride metabolite of halothane. The serum antibodies are specific to halothane hepatitis patients and are not seen in sera of patients with other types of liver pathology. In this study, a 57-kD trifluoroacetylated liver microsomal neoantigen associated with halothane hepatitis and native 57-kD protein were purified from liver microsomes of halothane-treated and -untreated rats, respectively. When the purified trifluoroacetylated 57-kD and native 57-kD proteins were used as test antigens in an enzyme-linked immunosorbent assay, serum antibodies from halothane hepatitis patients (n = 40) reacted with both of these proteins to a significantly greater extent than did serum antibodies from control patients (n = 32). On the basis of its apparent monomeric molecular mass, isoelectric point and NH2-terminal amino acid and tryptic peptide sequences, the 57-kD protein has been identified as rat liver protein disulfide isomerase. Antibodies raised against rat liver protein disulfide isomerase also reacted with a protein of approximately 58-kD in human liver microsomes. The results of this investigation suggest that trifluoroacetylated protein disulfide isomerase is one of the immunogens associated with halothane hepatitis. In certain patients it might lead either to specific antibodies or, possibly, to specific T cells, which could be responsible for halothane hepatitis.

Induction of an auto-anti-IgE response in rats. IV. Effects on mast cell degranulation

Induction of an auto-anti-IgE (auto-aIgE) response in the rat inhibits both total and specific IgE production and alters the distribution of mast cell (MC) subpopulations identified by differential Alcian blue/safranin staining. We have extended these observations by characterizing the auto-aIgE antibodies and determining their effects on MC degranulation in vitro and in vivo. An auto-aIgE response was induced in bacillus Calmette-Guérin (BCG)-primed rats by injecting a conjugate of highly purified rat IgE myeloma (IR2) coupled to tuberculin-derived purified protein derivative (PPD). Anti-IgE autoantibodies were almost exclusively IgG2a. The intradermal injection of auto-aIgE into untreated rats induced local MC degranulation as shown by a strong immediate skin response. Histologically there was evidence of significant degranulation of safranin staining connective tissue MC (SMC) in the skin but not of the Alcian blue staining MC (ABMC) in the sub-epidermal region. The induced degranulation was epsilon-chain specific; immunopurified anti-idiotypic antibodies raised to the IgE IR2 myeloma had no MC degranulating activity. When administered locally, auto-aIgE inhibited a subsequent passive cutaneous anaphylaxis (PCA) response elicited by anti-ovalbumin IgE. In addition, the PCA response was significantly decreased in animals with an ongoing auto-aIgE response. Immunopurified auto-aIgE also induced histamine release in vitro from rat peritoneal MC. These results are discussed in the context of naturally occurring autoantibodies to IgE present in patients with allergic disease.

IgE-secreting cells in the thymus: correlation with induction of tolerance to IgE

We have shown previously that normal mice become tolerant to endogenous IgE when they are approximately 2 weeks old and that this corresponds closely with the initial appearance of IgE in serum. Tolerance evidently is restricted to T cells, since B cells responsive to IgE are present in neonatal and adult mice. The present report shows that IgE-secreting cells can be detected in the thymus between days 7 and 11 after birth and that the onset of tolerance to IgE occurs at the age of 11 days. Similar results were obtained in A/J and (BALB/c x A/J)F1 mice. This suggests that tolerance is induced in the thymus, probably by cells bearing peptide fragments of IgE. The order of appearance of IgE-secreting cells is thymus, spleen, and mesenteric lymph nodes.

Evidence for IgE immune complexes and distribution of IgG subclasses with anti-IgE activity in patients with atopic dermatitis

The anti-IgE autoantibody was detected, using a radioimmunoassay, in 17 out of 35 (48.6%) of patients with atopic dermatitis. Significant increased levels of IgG-anti-IgE were seen in the patients studied compared with the control group. The specificity of the anti-IgE autoantibody was confirmed by competitive inhibition assay using IgG, IgM, IgE myeloma. A correlation was observed between the levels of IgG-anti-IgE and serum IgE but not between the IgG subclasses with anti-IgE activity and the clinical status. These data demonstrate that the IgG subclass distribution with anti-IgE activity belongs mostly to the IgG1 and IgG4 subclasses compared with the controls. Moreover, ultracentrifugation analysis indicated that the IgG-anti-IgE in the serum samples from the patients with atopic dermatitis was present in the form of an immune complex with self-IgE. These observations may suggest that the anti-IgE complexes may play a broader role in the modulation of the immune response and that this autoantibody may mask recognition of IgE in conventional assays.

Inhibition of IgE synthesis by anti-IgE: role in long-term inhibition of IgE synthesis by neonatally administered soluble IgE

Inoculation of syngeneic IgE into 2- to 12-day-old mice results in prolonged synthesis of anti-IgE antibodies without further challenge. These anti-IgE antibodies may be largely responsible for the long-term inhibition of synthesis of IgE that is known to result from a perinatal challenge with IgE. This conclusion is supported by the effect of passive inoculation of syngeneic polyclonal anti-IgE antibodies into young mice, which similarly results in selective inhibition of IgE synthesis. Further evidence is the close relationship between the age dependency of IgE-induced inhibition of subsequent IgE synthesis and the ability of IgE to induce anti-IgE antibodies. IgE synthesis was monitored at the level of secretion by B cells as well as serum IgE levels and IgE antibody responses.

IgG anti-IgE from atopic dermatitis induces mediator release from basophils and mast cells

IgG antibodies containing anti-IgE activity isolated from a patient with atopic dermatitis (H-aIgE) induced mediator release from human basophils and mast cells isolated from skin and lung tissues. The release of histamine was calcium- and temperature-dependent and did not involve cytotoxicity. There was an excellent correlation (r = 0.88; p less than 0.001) between the maximum percent histamine release from human basophils induced by rabbit anti-IgE (R-aIgE) and H-aIgE. H-aIgE was approximately 30 times more potent than R-aIgE in inducing mediator release from human basophils, skin, and lung mast cells. H-aIgE specifically desensitized human basophils to a subsequent challenge with both H-aIgE and R-aIgE. Lactic acid removal of IgE from human basophils blocked the releasing activity of both R-aIgE and H-aIgE. Passive sensitization with hyperimmune sera or purified IgE myeloma restored the response of basophils to both R-aIgE and H-aIgE. IgE purified from three different myeloma patients concentration-dependently blocked the histamine releasing activity of both R-aIgE and H-aIgE.

Induction of an auto-anti-IgE response in rats. III. Inhibition of a specific IgE response

An auto-anti-IgE response was induced in conventional (PVG-RT1U and high IgE-producing (BN) rat strains by immunization with a highly purified rat IgE myeloma IR2. Earlier work established that total serum IgE levels were decreased by this procedure (Marshall & Bell, 1985) but only in the PVG-RT1U strain. IR2-immunized rats were tested for their ability to produce a specific IgE response to ovalbumin (OVA). The primary anti-OVA IgE response was inhibited by 60-75% in both rat strains, regardless of whether the total serum levels of IgE were reduced. The secondary IgE response to OVA was also inhibited in anti-IgE-producing animals but not in rats primed with OVA before anti-IgE induction. The inhibition of the anti-OVA response was isotype specific; the IgG response to OVA was unaffected. These studies may help elucidate the regulatory role played by naturally occurring anti-IgE antibodies found particularly in atopic individuals.

Immunological responsiveness of neonatal A/J mice to isotypic determinants of syngeneic IgE

We have previously shown that adult A/J mice produce high titers of anti-IgE with isotypic or idiotypic specificities in response to challenge with a conjugate of KLH with syngeneic monoclonal IgE. Thus, B cells that can synthesize anti-IgE are present in the mice. Adult mice are unresponsive to unconjugated IgE in CFA, suggesting that tolerance exists at the level of T cells. The present study shows that neonatal mice produce anti-IgE antibodies in response to unconjugated IgE in CFA, but that this capacity is lost after the age of 2-3 wk. The loss of responsiveness corresponds closely with the appearance of detectable IgE in serum, suggesting that the IgE may induce tolerance. The affinities of anti-IgE antibodies produced by neonatal mice fall in the range of values obtained with KLH-IgE in adult mice. Tolerance to unconjugated IgE in CFA can be induced in neonatal mice by administration of IgE in saline. In addition, the tolerant state can be induced by adoptive transfer of spleen cells from adult mice. The time-dependent acquisition of tolerance provides a useful model for studying mechanisms of tolerance and autoimmunity.

Induction and properties of syngeneic murine anti-immunoglobulin D

High titers of autoantibodies directed to isotypic determinants of IgD were produced by inoculation of syngeneic monoclonal IgD, conjugated covalently to keyhole limpet hemocyanin, into adult or neonatal inbred mice. Anti-idiotypic antibodies were induced at the same time. The average affinity of the mouse antibodies (Ka approximately equal to 10(7) M-1) is similar to that of rabbit anti-IgD and of syngeneic anti-IgE induced by the same procedure. Results indicate that B cells of the mice are not tolerant to serum IgD and that tolerance is maintained at the level of T cells. Direct interaction of the syngeneic anti-IgD with cell-surface IgD was minimal, and there was no convincing evidence that cell-surface IgD was down-regulated in the anti-IgD-producing mice. Further studies, preferably employing monoclonal anti-IgD, are required to determine whether epitopes on cell-surface IgD can be recognized by syngeneic anti-IgD. The ability to generate in vivo high titers of anti-IgD should facilitate the production of such monoclonal antibodies.