IgE class-restricted tolerance induced by neonatal administration of soluble or cell-bound IgE

Abrogation and homeostatic restoration of IgE responses by a universal IgE allergy CTL vaccine-The three signal self/non-self/self (S/NS/S) theory

Natural IgE cytotoxic peptides (nECPs), which are derived from the constant domain of the heavy chain of human IgE producing B cells via endoplasmic reticulum (ER) stress, are decorated onto MHC class 1a molecules (MHCIa) as unique biomarkers for CTL (cytotoxic T lymphocyte)-mediated immune surveillance. Human IgE exhibits only one isotype and lacks polymorphisms; IgE is pivotal in mediating diverse, allergen-specific allergies. Therefore, by disrupting self-IgE tolerance via costimulation, the CTLs induced by nECPs can serve as universal allergy vaccines (UAVs) in humans to dampen IgE production mediated by diverse allergen-specific IgE-secreting B cells and plasma cells expressing surface nECP-MHCIa as targets. The study herein has enabled the identification of nECPs, A32 and SP-1/SP-2 nonameric natural peptides produced through the correspondence principle. Vaccination using nECP induced nECP-specific CTL that profoundly suppressed human IgE production in vitro as well as chimeric human IgE production in human IgE/HLA-A2.01/HLA-B7.02 triple transgenic rodents. Furthermore, nECP-tetramer-specific CTLs were found to be converted into CD4 Tregs that restored IgE competence via the homeostatic principle, mediatepred by SREBP-1c suppressed DCs. Thus, nECPs showed causal efficacy and safety as UAVs for treating categorically type I hypersensitivity IgE-mediated allergies. The applied vaccination concept presented provides the foundation to unify, integrate through a singular class of tetramer-specific TCR clonotypes for regulaing human IgE production. The three signal theory pertains to mechanisms of three cells underlying central tolerance (S), breaking self tolerance (NS) and regaining peripheral tolerance (S) via homeostasis concerning nECP as an efficacious and safe UAV to treat type I IgE-mediated hypersensitivity. The three signal theory impirically extended, may be heuritic for immuno-regulation of adaptive immune repertoire in general.

Antibodies specific for a segment of human membrane IgE deplete IgE-producing B cells in humanized mice

IgE-mediated hypersensitivity is central to the pathogenesis of asthma and other allergic diseases. Although neutralization of serum IgE with IgE-specific antibodies is in general an efficacious treatment for allergic asthma, one limitation of this approach is its lack of effect on IgE production. Here, we have developed a strategy to disrupt IgE production by generating monoclonal antibodies that target a segment of membrane IgE on human IgE-switched B cells that is not present in serum IgE. This segment is known as the M1' domain, and using genetically modified mice that contain the human M1' domain inserted into the mouse IgE locus, we demonstrated that M1'-specific antibodies reduced serum IgE and IgE-producing plasma cells in vivo, without affecting other immunoglobulin isotypes. M1'-specific antibodies were effective when delivered prophylactically and therapeutically in mouse models of immunization, allergic asthma, and Nippostrongylus brasiliensis infection, likely by inducing apoptosis of IgE-producing B cells. In addition, we generated a humanized M1'-specific antibody that was active on primary human cells in vivo, as determined by its reduction of serum IgE levels and IgE plasma cell numbers in a human PBMC-SCID mouse model. Thus, targeting of human IgE-producing B cells with apoptosis-inducing M1'-specific antibodies may be a novel treatment for asthma and allergy.

IgE peptide-specific CTL inhibit IgE production: a transient IgE suppression model in wild-type and HLA-A2.1 transgenic mice

Effect of IgE peptide-specific CTL on IgE antibody production was studied in mouse models. CTL elicited in B6.A2Kb tg mice against a human IgE peptide nonamer, pWV, lysed human IgE-secreting U266 myeloma cells and inhibit IgE production by these cells. U266 transfected with mouse A2Kb transgene (U266-A2Kb) were optimally lysed by these CTL, because the alpha3 domain of A2Kb interacts well with the CD8 co-receptors. The CTL generated were more effective in inhibiting IgE production by U266-A2Kb cells than lysing these cells. IgE production by and progression of U266 myeloma were suppressed in B6.A2Kb tg mice rendered tolerant to these cells and vaccinated with pWV along with CpG. We also studied the CTL response elicited in wild-type mice by a mouse nonameric IgE peptide, PI-1, along with CpG. This treatment caused a transient suppression of the IgE response in mice previously sensitized to an antigen. In mice treated with this regimen repeatedly, the IgE response was fully recovered 20 days after each treatment. Notably, while IgE peptide/CpG-treated mice remained unresponsive to antigen challenge in vivo, antigen-specific IgE production can be elicited by antigen in cultured splenocytes from these mice. Moreover, IgE peptide/CpG also inhibited an on-going IgE response, including IgE production by bone marrow cells. Taken together, these observations indicate that a CTL-based IgE peptide vaccine targeting IgE-secreting B/plasma cells may be safely employed as a therapeutic approach for suppressing IgE production.

Cytotoxic T-cells specific for natural IgE peptides downregulate IgE production

Immunoglobulin E (IgE) plays a central role in IgE-mediated immediate type hypersensitivity. Since production of IgE depends on Th2, efforts to block IgE production and control allergic reactions include tolerization of Th2 or deviating development of Th2. We hypothesized that cytotoxic T lymphocytes targeting natural IgE peptides/MHC I complexes can eliminate IgE-producing cells and inhibit centrally IgE production. CTL to self-IgE peptides were elicited in mice immunized with nonameric p109-117, p113-121, and p103-141 (CHepsilon2 domain), which encompass both peptides with an OVA helper peptide (OVAp restricted for H-2d/b) in liposomes and presented by dendritic cells (DC). CTL from BALB/c lysed IgE peptide-pulsed P815 target as well as IgE-producing 26.82 hybridomas (H-2d). Natural tolerance to self-IgE peptides was tested in IgE sufficient (IgE +/+) as well as IgE-deficient (IgE -/-) 129/SvEv mice (H-2b). Comparable magnitude of CTL responses was observed in both strains immunized with p109-117 or p103-141 concomitantly with CD4 T-cell costimulation. CTL from 129/SvEv lysed not only IgE peptide-pulsed EL-4 but also IgE-producing B4 hybridomas (H-2b). This observation strongly suggests a correspondence of epitope of immunogenic peptide to that of physiologically processed IgE peptides presented on IgE-producing cells. Moreover, CTL were generated in 129/SvEv, immunized with the recombinant antigenized antibody in liposomes encompassing p107-123, p109-117, and p113-121 expressed in CDR3 of VH62/human gamma1. Polyclonal IgE production was inhibited by coincubation with MHC I-restricted CTL in vitro. Furthermore, antigen-specific IgE responses were inhibited in mice, immunized with p109-117 and p103-141 while IgG responses were not suppressed. Since IgE peptide sequences of CHepsilon2 are ubiquitous to all murine IgE heavy chain, peptides made as such can serve as a universal IgE vaccine to prevent allergy for a myriad of allergens in rodents. This observation suggests that similar human IgE peptides should be identified and employed to downregulate human IgE production.

Peptides derived from IgE heavy chain constant region induce profound IgE isotype-specific tolerance

(BALB/c x SJL)F1 mice, perinatally injected with peptide-N-glyconase F-treated, deglycosylated IgE heavy chain or recombinant IgE heavy chain (CH epsilon 2-CH epsilon 4), were profoundly inhibited in antigen-specific IgE production. There exist minimally two tolerogenic IgE peptides, residing in the CH epsilon 2 and CH epsilon 4 domains. Peptide I, generated by V8 protease, comprises 39 amino acids within CH epsilon 2, beginning at amino acid 103. Peptide E begins at amino acid 312 of the CH epsilon 4 domain and extends through the CH epsilon 4 domain. The total lack of antigen-specific IgE responses in IgE peptide-treated mice was not due to overproduction of interferon-gamma, nor lack of interleukin (IL)-4, as predicted by the Th2/IL-4 paradigm for IgE production. IgE-tolerant mice exhibited comparable levels of circulating anti-IgE antibodies to those of PBS-treated control mice. IgG obtained from sera of both sources failed to inhibit IgE responses in vitro. Moreover, IgE responses of spleen cells from IgE peptides-treated mice were restored by CD4+ T cells from PBS-treated control mice. We hypothesize that regulation of antigen-specific IgE responses is mediated by CD4+ T cells which normally recognize IgE peptides on IgE precursor B cells, and can be rendered tolerant by perinatal IgE peptide treatment.

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.

Anti-IgE therapy

Controlling the IgE response at either the synthesis level or the effector phase should have a profound impact on the allergic cascade. For more than a decade, researchers have focused on ways of interfering with the binding of IgE to its high-affinity receptor on proinflammatory cells. Several approaches have also been taken to antagonize the complex interplay of cytokines and cell-associated molecules (CD40, CD23) that are implicated in IgE synthesis. Recently, anti-IgE antibodies have been developed that are potent IgE antagonists. These antibodies are currently under clinical investigation as potential therapeutics for allergic disease.

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.

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.

Genesis of host IgE competence: perinatal IgE tolerance induced by IgE processed and presented by IgE Fc receptor (CD23)-bearing B cells

A murine model for studying life-long IgE tolerance was previously developed in this laboratory by perinatal IgE injection into neonates. Herein, we demonstrated that normal and immortal CD23+ B cell lines presented processed IgE via CD23-mediated endocytic pathway and triggered perinatal IgE tolerance. The observations were as followed: (a) CD23 on normal B cells or B cell hybridomas mediated IgE-dependent perinatal IgE tolerance and total IgE deficiency; and lack of either antigen-specific IgE or total IgE did not correlate with elevated levels of autologous anti-IgE in individual mice; (b) IgE tolerance-inducing capacity of CD23+ B cell hybridomas was augmented by treatment with antigen-IgE complexes or interleukin 4, and significantly inhibited by anti-CD23 prior to IgE pulsing; (c) antigen-IgE complexes were endocytosed and degraded in acid hydrolases-containing vesicles; and IgE tolerance was abrogated by treating IgE-pulsed 17A11 at 4 degrees C or 20 degrees C followed immediately by fixation, and by treating IgE-pulsed 17A11 with metabolic inhibitors that elevated intracellular pH of the endocytic vesicles. In conclusion, this study suggested that one pivotal step of genetic control of IgE responses may be exercised at the early developmental stage of T cells of the IgE lineage, and that CD23 may facilitate capture of endogenously secreted IgE, and mediate endocytic processing and presentation of self IgE epitope(s), and thus contribute to the genesis of host IgE competence.

What determines an antigen-specific IgE isotypic response? A hypothesis

Two models to account for an antigen-specific IgE isotypic response are proposed. Both models assume a first-tiered IgE production induced by antigen and IL-4; however, the processed IgE or Ag-IgE immune complexes stimulate T epsilon cells differently in the two models. In Model I, we propose that T epsilon cells express conventional T-cell receptors which recognize IgE isotypic determinants. Model IA proposes that IgE fragments are processed and recognized along with class II MHC molecules, and T epsilon cell preferentially act on antigen-activated IgE-committed B epsilon cells via recognition of processed membrane IgE determinants but not antigens; thus T epsilon cells are in principle capable of modulating non-antigen-specific polyclonal IgE responses. Model IB proposes that IgE function as a class-restriction determinant for nominal antigens analogous to that of class II molecules, and T epsilon cells exert stringent antigen-specific IgE isotypic responses by recognizing nominal antigens restricted to IgE. T epsilon cells thus exert antigen-specific and IgE concerted immunoregulation, and do not participate in modulating polyclonal IgE production. Model II proposes a heterotypic interaction of IgE with a cell interaction receptor (or IgE Fc receptor) on T cells. T epsilon cells modulate antigen-specific IgE isotypic responses via ligation with IgE-antigen immune complexes on B-cell surface; thus, T epsilon cells in principle contribute to polyclonal IgE responses.

Mechanisms of IgE tolerance: dual regulatory T cell lesions in perinatal IgE tolerance

The mechanisms of genetic control of IgE responses are exercised at different immuno-physiological levels. This study centered upon the development of IgE lineage-specific regulatory T cells. Herein, we demonstrate the following points: (a) perinatal administration of soluble self IgE molecule or self IgE complexed with foreign antigen induces IgE tolerance as manifested by antigen-specific IgE unresponsiveness and a generalized IgE immunodeficiency, and the induction of IgE tolerance does not affect antigen-specific IgG1, IgG, and IgA responses; (b) inducibility of perinatal IgE tolerance is correlated with complete absence of endogenously secreted IgE in the neonates; and the state of persistent IgE tolerance also does not correlate with the presence of high levels of circulating anti-IgE autoantibodies; (c) The lesions induced during the ontogeny of IgE antibody system do not appear to result from an imbalance of production of interleukin 4 and interferon-gamma by T helper Th2 and Th1 cells in antigen-stimulated cultures; the dual immunoregulatory lesions in T cell subsets are demonstrated: clonal anergy/deletion of CD4+ IgE Th cells and the presence of CD8+ IgE suppressor cells induced by perinatal IgE treatment. We propose that antigen/interleukin 4 activated B cells are controlled by IgE lineage-specific regulatory T cells which recognize self IgE determinant(s) on IgE committed B cells. Life-long IgE tolerance ensues as a result of a new steady state of IgE lineage-specific CD4+ and CD8+ T cell subsets.

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.

Suppression of IgE responses by hyperimmune serum in rats

Recent work has shown that a relatively long-lasting suppression of egg albumin (EA)-specific IgE responsiveness occurs in the progeny of EA-immunized mother rats. This phenomenon can be duplicated by a course of EA-immune serum injections given to the neonatal progeny of normal mothers, and antigen-specific IgG was found to be the effective mediator. In order to elucidate further the mechanism of this selective suppression, the capacity of immune serum to suppress IgE responsiveness in adults was investigated. Pretreatment of adults with hyperimmune serum 3 weeks in advance of immunization was as effective as when the animals were neonatally treated. The possibility that the mediator responsible is the very small amount of EA-specific IgG remaining at the time of immunization was tested by injecting a small volume of immune serum simultaneously with immunization. This treatment also suppressed IgE responsiveness. The possibility that low levels of EA-specific antibody form complexes with the immunizing antigen is discussed.

Suppression of the anti-hapten IgE antibody response with hapten-modified spleen cells

Spleen cells of BALB/c mice were chemically modified with phosphorylcholine or benzylpenicilloyl hapten. The i.v. administration of such cells into syngeneic animals suppressed the formation of specific IgE antibodies against the respective hapten. The IgE antibody response against ovalbumin, which was used as an immunogenic carrier for the haptens, was not affected and the anti-hapten IgG or IgG1 response remained at the levels of the controls. The suppression could be transferred into X-irradiated mice by T cells from tolerized animals. Moreover, it was demonstrated that not only the induction of IgE, but also an established anti-hapten IgE antibody response is accessible to suppression by treatment with hapten-modified spleen cells from syngeneic animals. The results indicate that the i.v. administration of antigen coupled to syngeneic spleen cells induces T cells which suppress the formation of specific IgE antibodies in the primary and the secondary response without significantly affecting the formation of IgG antibodies.

Hybrid antibodies can target sites for attack by T cells

It would be advantageous in the case of certain diseases to be able to focus a strong T-cell response at a chosen target, for example, in treating cancer or infections that have escaped the normal host response. At present, it seems inconceivable that we could use antigen-specific lines or clones of effector T cells for this purpose because of complications due to the major histocompatibility restriction of T-cell specificity and the problem of rejection of transplanted effector cells. Here we describe a novel technology which combines the power of T lymphocytes in eliminating unwanted cells and causing beneficial inflammatory reactions with the great advantages of monoclonal antibodies (their specificity and availability). We show that heteroconjugates of monoclonal antibodies (referred to hereafter as hybrid antibodies), in which one of the component binding sites is anti-T-cell receptor and the other component binding site is directed against any chosen target antigen, can focus T cells to act at the targeted site. Monoclonal antibodies directed against the T-cell receptor, such as the anti-allotype used here, are mitogenic for resting T cells and can be used to induce effector T cells carrying the T-cell receptor determinant which can then be directed against the target by a hybrid antibody.

Induction of an auto-anti-IgE response in rats I. Effects on serum IgE concentrations

With a view to specifically suppressing the IgE isotype, rats of high (BN) and low (PVG.RT1u) IgE-responding phenotypes were immunized with a highly purified rat IgE myeloma (IR2) in an attempt to induce an anto-anti-IgE response. Rat IgE antibodies against epsilon determinants were detected in the serum of IR2-immunized animals using a solid-phase (plate) radioimmunoassay. The auto-anti-IgE antibodies detected were found to bind to IR2, to a second rat IgE myeloma (IR162) and to mouse monoclonal IgE but not rat IgG. The specificity of the anti-epsilon binding was shown by inhibition studies. The raising of an auto-anti-IgE response in PVG.RT1u rats severely depleted the serum level of circulating IgE for at least 8 weeks. In BN rats, immunization with IR2 caused marked fluctuations in serum IgE levels. The rats in both strains remained healthy throughout the experiment. The rate and route of IgE break down was not altered in anti-IgE-producing rats. The relevance of the present model in understanding and possibly controlling allergic disorders is considered.

IgE class-restricted tolerance induced by neonatal administration of soluble or cell-bound IgE. Cellular mechanisms

Certain aspects of the phenomenon of IgE class-restricted tolerance induced in mice by neonatal treatment with monoclonal IgE, either in soluble form or coupled to syngeneic spleen cells, were examined. The present studies document that this tolerance results from exposure to IgE molecules, irrespective of their antigen specificity, and the resulting effects are polyclonal in nature since IgE responses directed against antigenic determinants unrelated to the tolerance-inducing IgE molecules are affected. Moreover, such findings indicate that the molecular subregion(s) responsible for inducing IgE class-restricted tolerance resides in the epsilon heavy chain constant region domain(s) of IgE. When soluble IgE is employed, tolerance induction results from neonatal treatment with doses as low as 2.5 micrograms per injection per mouse; cell-bound IgE is considerably more potent, in terms of total dose required, since tolerance results from treatment with as few as 1 X 10(6) cells per injection (per mouse), equivalent to an absolute quantity of 0.2 ng of IgE per injection. This long-term class-specific tolerance appears to be a unique feature of the IgE antibody system, since treatment of mice with monoclonal antibodies of the IgA, IgG1, or IgG2b isotypes, either in soluble or cell-bound form, does not perturb antibody responses of their corresponding isotypes or in the IgE class. By analyzing the lymphoid cells of IgE-tolerant mice after they reached adulthood, the following observations were made: (a) lymphoid cells from such tolerant mice fail to develop FcR epsilon + cells upon in vitro stimulation with IgE, as is characteristically observed with lymphoid cells from nontolerant mice; and (b) mice rendered tolerant by neonatal treatment with soluble IgE possess IgE class-restricted suppressor T cells, demonstrable in adoptive transfer experiments, whereas no such suppressor cells are evident in mice in which cell-bound IgE was used for neonatal treatment. The latter observations could mean that two different mechanisms underlie the IgE class-restricted tolerance, or both mechanisms operate coordinately to varying degrees depending upon which regimen is used for tolerance induction, as discussed herein.

Mouse monoclonal IgE antibodies specific for ragweed pollen antigens

In order to obtain monoclonal IgE antibody specific for the major allergens in ragweed pollen extracts, hybridomas were constructed from spleens of mice immunized with ragweed antigen E (AgE). Two hybridomas were selected for thorough study, both secreting antibodies of the IgE class. Large quantities of IgE antibodies were isolated by affinity purification using Sepharose 4B conjugated with ragweed pollen proteins (Fraction A). Both MAbs were found to bind to a high molecular weight and heterogeneous population of proteins, but not to monomeric AgE as demonstrated by protein blot analysis. It is suspected that both MAbs react with low affinity with AgE determinants and binding could be demonstrated only with aggregated forms of AgE. Although the specific antigens with which they react are unknown, these monoclonal IgE antibodies should be useful reagents, complementing the previously obtained monoclonal anti-dinitrophenyl IgE antibody, for studying various aspects of the mouse and human IgE antibody systems.

Tolerance for self IG at the level of the Ly1+ T cell

Experiments presented in this report demonstrate that specificity of the Ly1+ T cell proliferative response to NP-modified Ig is controlled by Igh-C-linked genes. In addition, we describe the mechanism whereby Igh-C-encoded molecules influence Ly1+ T cell activity. We show that Igh-C-linked control of T cell responses to NP-modified Ig is a secondary consequence of naturally acquired tolerance for self Ig. Unresponsiveness to self Ig is not due to a defect expressed functionally at the level of the antigen-presenting cell, nor is it associated with active suppression. These results suggest that tolerance for self Ig at the level of the Ly1+ T cell is due to functional deletion of Ly1+ T cell clones specific for self Ig. The possibility is considered that regulatory effects mediated by passively administered antibodies may in part be due to induction of Ly1+ T cell tolerance for self Ig.