Probing into the realm of proteins and immunity.
Explore the source record for details and available documents.
Allergy and Immunology↗
Biomedical subjects
M Sela
Publications and source records attributed to M Sela.
Effect of natural beta-carotene supplementation in children exposed to radiation from the Chernobyl accident.
Attempts were made to evaluate 709 children (324 boys and 385 girls) who had been exposed long-term to different doses of radiation during and after the Chernobyl accident and had moved to Israel between 1990 and 1994. Upon arrival, all of them underwent a check-up for most common clinical disorders and were then divided into three groups according to their residences (distance from the reactor) and the level of irradiation exposure: no radiation, <5 Ci/m2, and >5 Ci/m2, respectively. Blood serum analyses for total carotenoids, retinol, alpha-tocopherol and oxidized conjugated dienes in 262 of the children showed increased HPLC levels of conjugated dienes, indicating increased levels of oxidation of in vivo blood lipids in children from the contaminated areas. The levels were higher in girls than in boys. Some 57 boys and 42 girls were given a basal diet with a diurnal supplementation of 40 mg natural 9-cis and all-trans equal isomer mixture beta-carotene in a capsulated powder form of the alga Dunaliella bardawil, for a period of 3 months. Blood serum analyses were regularly conducted before supplementation to determine the baseline effect of radiation exposure to the children, after 1 and 3 months of natural beta-carotene supplementation. After supplementation, the levels of the oxidized conjugated dienes decreased in the children's sera without any significant changes in the level of total carotenoids, retinol or alpha-tocopherol. Other common blood biochemicals were within the normal range for all tests and no statistical differences before or after supplementation of beta-carotene were noted. High pressure liquid chromatography (HPLC) analyses for carotenoids in the blood detected mainly oxycarotenoids, and to a lesser extent, all-trans beta-carotene, alpha-carotene, but not 9-cis beta-carotene. The results suggest that irradiation increases the susceptibility of lipids to oxidation in the Chernobyl children and that natural beta-carotene may act as an in vivo lipophilic antioxidant or radioprotector.
Adolescent↗
Copolymer 1 induces T cells of the T helper type 2 that crossreact with myelin basic protein and suppress experimental autoimmune encephalomyelitis.
The synthetic amino acid copolymer copolymer 1 (Cop 1) suppresses experimental autoimmune encephalomyelitis (EAE) and is beneficial in multiple sclerosis. To further understand Cop 1 suppressive activity, we studied the cytokine secretion profile of various Cop 1-induced T cell lines and clones. Unlike T cell lines induced by myelin basic protein (MBP), which secreted either T cell helper type 1 (Th1) or both Th1 and Th2 cytokines, the T cell lines/clones induced by Cop 1 showed a progressively polarized development toward the Th2 pathway, until they completely lost the ability to secrete Th1 cytokines. Our findings indicate that the polarization of the Cop 1-induced lines did not result from the immunization vehicle or the in vitro growing conditions, but rather from the tendency of Cop 1 to preferentially induce a Th2 response. The response of all of the Cop 1 specific lines/clones, which were originated in the (SJL/JxBALB/c)F1 hybrids, was restricted to the BALB/c parental haplotype. Even though the Cop 1-induced T cells had not been exposed to the autoantigen MBP, they crossreacted with MBP by secretion of interleukin (IL)-4, IL-6, and IL-10. Administration of these T cells in vivo resulted in suppression of EAE induced by whole mouse spinal cord homogenate, in which several autoantigens may be involved. Secretion of anti-inflammatory cytokines by Cop 1-induced suppressor cells, in response to either Cop 1 or MBP, may explain the therapeutic effect of Cop 1 in EAE and in multiple sclerosis.
Adjuvants, Immunologic↗
Bivalence of EGF-like ligands drives the ErbB signaling network.
Signaling by epidermal growth factor (EGF)-like ligands is mediated by an interactive network of four ErbB receptor tyrosine kinases, whose mechanism of ligand-induced dimerization is unknown. We contrasted two existing models: a conformation-driven activation of a receptor-intrinsic dimerization site and a ligand bivalence model. Analysis of a Neu differentiation factor (NDF)-induced heterodimer between ErbB-3 and ErbB-2 favors a bivalence model; the ligand simultaneously binds both ErbB-3 and ErbB-2, but, due to low-affinity of the second binding event, ligand bivalence drives dimerization only when the receptors are membrane anchored. Results obtained with a chimera and isoforms of NDF/neuregulin predict that each terminus of the ligand molecule contains a distinct binding site. The C-terminal low-affinity site has broad specificity, but it prefers interaction with ErbB-2, an oncogenic protein acting as a promiscuous low-affinity subunit of the three primary receptors. Thus, ligand bivalence enables signal diversification through selective recruitment of homo- and heterodimers of ErbB receptors, and it may explain oncogenicity of erbB-2/HER2.
Animals↗
A subclass of tumor-inhibitory monoclonal antibodies to ErbB-2/HER2 blocks crosstalk with growth factor receptors.
ErbB-2 is an orphan receptor that belongs to a family of tyrosine kinase receptors for either epidermal growth factor (EGF) or Neu differentiation factor (NDF/neuregulin). Because overexpression of the erbB-2 proto-oncogene is frequently associated with an aggressive clinical course of certain human adenocarcinomas, the encoded protein is an attractive target for immunotherapy. Indeed, certain monoclonal antibodies (mAbs) to ErbB-2 effectively inhibit tumor growth in animal models and in clinical trials, but the underlying mechanism is incompletely understood. To study this question, we generated a large battery of mAbs to ErbB-2, that were classified epitopically. Whereas most antibodies stimulated tyrosine phosphorylation of ErbB-2, their anti-tumor effect correlated with its accelerated endocytic degradation. One group of tumor-inhibitory mAbs (Class II mAbs) was elicited by the most antigenic site of ErbB-2, and inhibited in trans binding of NDF and EGF to their direct receptors. The inhibitory effect was due to acceleration of ligand dissociation, and it resulted in the reduction of the ability of ErbB-2 to transactivate the mitogenic signals of NDF and EGF. These results identify two potential mechanisms of antibody-induced therapy: acceleration of ErbB-2 endocytosis by homodimerization and blocking of heterodimerization between ErbB-2 and growth factor receptors.
Animals↗
A peptide composed of tandem analogs of two myasthenogenic T cell epitopes interferes with specific autoimmune responses.
Myasthenia gravis (MG) is a T cell-regulated, antibody-mediated autoimmune disease. Two peptides representing sequences of the human acetylcholine receptor alpha-subunit, p195-212 and p259-271, were previously shown to stimulate peripheral blood lymphocytes of patients with MG and were found to be immunodominant T cell epitopes in SJL and BALB/c mice, respectively. Single amino acid substituted analogs of p195-212 (analog Ala-207) and p259-271 (analog Lys-262) were synthesized. We showed that analogs Ala-207 and Lys-262 inhibited, in vitro and in vivo, the proliferative responses of T cell lines specific to the relevant peptide and lymph node cells of mice immunized to p195-212 and p259-271, respectively. To inhibit T cell responses to both peptides (p195-212 and p259-271), we synthesized dual analogs composed of the tandemly arranged two single (Ala-207 and Lys-262) analogs (dual analog) either sequentially (Ala-207-Lys-262) or reciprocally (Lys-262-Ala-207). In the present study, we report that both dual analogs could bind to major histocompatibility complex class II molecules on antigen-presenting cells of SJL and BALB/c mice. Analog Lys-262-Ala-207, which bound more efficiently to major histocompatibility complex class II molecules, was found to inhibit the proliferative responses of both p195-212- and p259-271-specific T cell lines. Furthermore, the analog inhibited the in vivo priming of lymph node cells of both SJL and BALB/c mice when administered i.v., i.p., or per os. The dual analog Lys-262-Ala-207 could also immunomodulate myasthenogenic manifestations in mice with experimental autoimmune MG induced by inoculation of a pathogenic T cell line. Thus, a single peptide that is composed of analogs to two epitope specificities can be used to regulate T cell responses and disease associated with each epitope.
Amino Acid Sequence↗
Cop 1 as a candidate drug for multiple sclerosis.
Copolymer 1 (Cop 1), a synthetic copolymer of amino acids, is very effective in suppression of experimental autoimmune encephalomyelitis (EAE), the animal model for multiple sclerosis (MS). Cop 1 was found incapable of inducing EAE, yet it suppressed EAE in a variety of animal species, including primates. The immunological cross-reaction between the myelin basic protein (MBP) and Cop 1 serves as the basis for the suppressive activity of Cop 1 in EAE, by the induction of antigen-specific suppressor cells and competition with MBP for binding to major histocompatibility complex (MHC) molecules. Clinical trials with Cop 1, both Phase II and Phase III, were performed in relapsing-remitting (E-R) patients. The latter, a two-year multicenter double blind trial with 251 participating patients was conducted at 11 leading medical centers in the USA. It demonstrated a significant beneficial effect of Cop 1 in both diminishing the rate of exacerbations and improving the clinical status. The side effects of Cop 1 were only minimal. The cumulative results indicate that Cop 1 is a promising candidate drug for multiple sclerosis.
Animals↗
Copolymer 1: from basic research to clinical application.
Copolymer 1 (Cop-1) is a synthetic amino acid copolymer effective in suppression of experimental allergic encephalomyelitis (EAE). The suppressive effect of Cop-1 in EAE is a general phenomenon and is not restricted to a particular species, disease type or encephalitogen used for EAE induction. In phase III clinical trials Cop-1 was found to slow progression of disability and reduce the relapse rate in exacerbating-remitting multiple sclerosis (MS). In vivo and in vitro studies suggest that the mechanism for Cop-1 activity in EAE and MS involves the binding of Cop-1 to major histocompatibility complex class II molecules as an initial step. This binding results both in competition with myelin antigens for T-cell activation and in induction of specific suppressor cells of the Th2 type. As an antigen-specific intervention, Cop-1 has the advantage of reduced probability of long-term damage to the immune system.
Animals↗
Studies on the mechanism and specificity of the effect of the synthetic random copolymer GLAT on graft-versus-host disease.
Graft-versus-host disease (GVHD), which occurs when donor T-cells recognize multiple minor host histocompatibility antigens as non-self, presents the major limitation to successful allogeneic bone-marrow transplantation. The synthetic random copolymer of the amino acids, L-Glu, L-Lys, L-Ala and L-Tyr, termed GLAT, with promiscuous binding to multiple MHC class II alleles, reduces the incidence, onset and severity of disease in the BIO.D2 --> BALB/c model of lethal GVHD. GLAT inhibited the proliferative response towards host of both spleen cells from mice with GVHD and also of the effector T cell line established from these mice. Administration of GLAT for a limited period after transplantation completely abolished the cytotoxic activity toward host cells exerted by spleen cells from mice with GVHD. Whereas spleen and bone marrow cells from control mice with GVHD secreted IL-2 and INF-gamma when cocultured with host cells, these inflammatory cytokines could not be detected in supernatants of cells from GLAT treated mice. Moreover spleens and bone marrow cells from GLAT treated mice secreted small but significant amounts of IL-4 and IL-6 when cocultured with GLAT, suggesting that GLAT not only inhibits pro-GVHD cytokines but also causes a beneficial effect by inducing secretion of Th2 type cytokines. GLAT binds strongly to MHC molecules of host as well as donor haplotype. D-GLAT, identical to GLAT but composed of D-amino acids is also effective in preventing GVHD. D-GLAT does not cross-react with L-GLAT, but still binds strongly to MHC-class II molecules. These findings indicate that MHC blocking is involved in the therapeutic effect of GLAT on GVHD. The cumulative data demonstrate that GLAT modulates the effector mechanisms involved in GVHD, and can be potentially used for the prevention of GVHD across minor histocompatibility barriers.
Animals↗
Binding of copolymer 1 and myelin basic protein leads to clustering of class II MHC molecules on antigen-presenting cells.
Copolymer 1 (Cop 1), a synthetic copolymer of amino acids, effective in suppression of experimental allergic encephalomyelitis (EAE) and myelin basic protein (MBP), was shown to bind extensively and promiscuously to the class II MHC molecules on antigen-presenting cells (APC) without prior processing. In the case of human APC, binding has earlier been demonstrated to DR but not DQ or class I molecules. In the present study, we examined whether binding of Cop 1 and MBP affects MHC class II expression on the cell membrane. Biotinylated derivatives of these antigens were used to monitor their direct binding to MHC molecules on living APC by flow cytometry using phycoerythrin-streptavidin, while the levels of MHC surface expression were monitored by staining with FITC-conjugated anti-class I- and class II-specific antibodies. When Cop 1 or MBP were incubated with the APC, intensity of cell staining with anti-DR, but not with anti-DQ or anti-class I antibodies, was significantly increased, compared to the staining of control APC not reacted with these antigens. In contrast, staining intensity was unaffected when p84-102, a human immunodominant epitope of MBP, or ovalbumin (OVA), a protein which undergoes proteolytic degradation prior to binding, were incubated with the APC. Cycloheximide, a protein synthesis inhibitor, had no effect on the enhanced staining intensity with anti-DR antibody of cells treated with Cop 1 or MBP, whereas it inhibited the enhanced staining of both DR and DQ molecules caused by the respective antibodies, in the absence of these antigens. Brefeldin A, a protein transport inhibitor, lowered the levels of staining intensity with anti-DR and anti-DQ antibodies in both cases, with and without antigen added to the APC. Fluorescence microscopic analysis revealed that cells incubated with Cop 1 or MBP, but not with p84-102 or OVA, exhibit both bright staining of the cell membrane and clusters produced by the aggregation of DR molecules with these antigens. Taken together, these observations indicate that Cop 1 and MBP, due to their polyvalent character, lead to increased fluorescence intensity of their complexes with HLA-DR, possibly due to recruitment and clustering of previously synthesized DR molecules. This can explain the efficient binding of these antigens to the MHC class II molecules.
Adjuvants, Immunologic↗
Different roles of D-amino acids in immune phenomena.
Peptides and polypeptides either fully or partially built of D-amino acids interest researchers because of their advantages over all L peptides and polypeptides. In exploiting these characteristics, one should realize that the resulting molecules are nonetheless not inert, but rather may induce a unique immune response, which is hardly cross-reactive with the L-enantiomer. Moreover, cross-reaction between the L- and the D-sequences is limited also at the T cell level, probably due to different sterical conformations of the MHC-antigen-T cell receptor complexes formed. Polypeptides built exclusively of D-amino acids lead to antibody formation only at a relatively low concentration, otherwise they provoke immunological paralysis. The specificity of the immune response toward peptides containing D-amino acid residues is exquisite, and often D-amino acids play a dominant role in defining the specificity. Polypeptides composed exclusively of D-amino acids are thymus-independent antigens. Nevertheless, it is possible to prepare against them highly specific T cell hybridomas. In future plans for synthetic vaccines against infectious or autoimmune diseases, the inclusion of D-amino acids may be an advantage in terms of both specificity and efficacy, the latter because of longer persistence in an undigested form because they resist enzymatic degradation.
Amino Acids↗
Reactivity of T cells from seronegative patients with myasthenia gravis to T cell epitopes of the human acetylcholine receptor.
Seronegative (SN) patients with myasthenia gravis (MG) have clinical and electrophysiologic features similar to those of seropositive (SP) patients, and they respond to the same therapeutic measures. However, because SN patients lack detectable (by standard radioimmunoassays) serum antibodies to acetylcholine receptor (AChR), which are considered to have a crucial role in MG, the pathophysiologic basis for the disease is not clear. We therefore compared the ability of peripheral blood lymphocytes (PBL) of SN patients (11) and SP patients (39) to respond to myasthenogenic T cell epitopes of human AChR. We tested two aspects that relate to T-cell immunity: 1) T cell responses to myasthenogenic peptides by proliferation and IL-2 production, and 2) the ability of antigen-presenting cells to bind these T-cell epitopes. T cells of SN patients did not differ from those of SP patients in their ability to respond and to bind the two human AChR-derived myasthenogenic peptides. This supports the belief that most SN patients indeed suffer from an autoimmune disease directed against the AChR. The presence of T-cell immunity in the absence of antibodies may emphasize the importance of AChR-specific T cells in MG.
Adult↗
Copolymer 1 from the laboratory to FDA.
Explore the source record for details and available documents.
Adjuvants, Immunologic↗
Diversification of Neu differentiation factor and epidermal growth factor signaling by combinatorial receptor interactions.
The ErbB family includes two receptors, ErbB-1 and ErbB-3, that respectively bind to epidermal growth factor and Neu differentiation factor, and an orphan receptor, ErbB-2. Unlike ErbB-1 and ErbB-2, the intrinsic tyrosine kinase of ErbB-3 is catalytically impaired. By using interleukin-3-dependent cells that ectopically express the three ErbB proteins or their combinations, we found that ErbB-3 is devoid of any biological activity but both ErbB-1 and ErbB-2 can reconstitute its extremely potent mitogenic activity. Transactivation of ErbB-3 correlates with heterodimer formation and is reflected in receptor phosphorylation and the transregulation of ligand affinity. Inter-receptor interactions enable graded proliferative and survival signals: heterodimers are more potent than homodimers, and ErbB-3-containing complexes, especially the ErbB-2/ErbB-3 heterodimer, are more active than ErbB-1 complexes. Nevertheless, ErbB-1 signaling displays dominance over ErbB-3 when the two receptors are coexpressed. Although all receptor combinations activate the mitogen-activated protein kinases ERK and c-Jun kinase, they differ in their rate of endocytosis and in coupling to intervening signaling proteins. It is conceivable that combinatorial receptor interactions diversify signal transduction and confer double regulation, in cis and in trans, of the superior mitogenic activity of the kinase-defective ErbB-3.
Animals↗
A synthetic random basic copolymer with promiscuous binding to class II major histocompatibility complex molecules inhibits T-cell proliferative responses to major and minor histocompatibility antigens in vitro and confers the capacity to prevent murine graft-versus-host disease in vivo.
Graft-versus-host disease (GVHD) is a T-cell-mediated disease of transplanted donor T cells recognizing host alloantigens. Data presented in this report show, to our knowledge, for the first time that a synthetic copolymer of the amino acids L-Glu, L-Lys, L-Ala, and L-Tyr (molecular ratio, 1.9:6.0:4.7:1.0; Mr, 6000-8500) [corrected], termed GLAT, with promiscuous binding to multiple major histocompatibility complex class II alleles is capable of preventing lethal GVHD in the B10.D2 --> BALB/c model (both H-2d) across minor histocompatibility barriers. Administration of GLAT over a limited time after transplant significantly reduced the incidence, onset, and severity of disease. GLAT also improved long-term survival from lethal GVHD: 14/25 (56%) of experimental mice survived > 140 days after transplant compared to 2/26 of saline-treated or to 1/10 of hen egg lysozyme-treated control mice (P < 0.01). Long-term survivors were documented to be fully chimeric by PCR analysis of a polymorphic microsatellite region in the interleukin 1beta gene. In vitro, GLAT inhibited the mixed lymphocyte culture in a dose-dependent fashion across a variety of major barriers tested. Furthermore, GLAT inhibited the response of nylon wool-enriched T cells to syngeneic antigen-presenting cells presenting minor histocompatibility antigens. Prepulsing of the antigen-presenting cells with GLAT reduced the proliferative response, suggesting that GLAT inhibits antigen presentation.
Animals↗
Peptide analogs to pathogenic epitopes of the human acetylcholine receptor alpha subunit as potential modulators of myasthenia gravis.
Myasthenia gravis is an autoimmune disease in which T cells specific to epitopes of the autoantigen, the human acetylcholine receptor, play a role. We identified two peptides, p195-212 and p259-271, from the alpha subunit of the receptor, which bound to major histocompatibility complex (MHC) class II molecules on antigen-presenting cells (APCs) from peripheral blood lymphocytes of myasthenia gravis patients and stimulated lymphocytes of >80% of the patients. We have prepared analogs of these myasthenogenic peptides and tested their ability to bind to MHC class II determinants and to interfere specifically with T-cell stimulation. We first determined relative binding efficiency of the myasthenogenic peptides and their analogs to APCs of patients. We found that single substituted analogs of p195-212 (Ala-207) and p259-271 (Lys-262) could bind to human MHC molecules on APCs as efficiently as the original peptides. Moreover, dual analogs containing the two single substituted analogs in one stretch (either sequentially, Ala-207/Lys-262, or reciprocally, Lys-262/Ala-207) could also bind to APCs of patients, including those that failed to bind one of the single substituted analogs. The single substituted analogs significantly inhibited T-cell stimulation induced by their respective myasthenogenic peptides in >95% of the patients. The dual analogs were capable of inhibiting stimulation induced by either of the peptides: They inhibited the response to p195-212 and p259-271 in >95% and >90% of the patients, respectively. Thus, the dual analogs are good candidates for inhibition of T-cell responses of myasthenia gravis patients and might have therapeutic potential.
Adult↗
Coupling of the c-Cbl protooncogene product to ErbB-1/EGF-receptor but not to other ErbB proteins.
The ErbB family of transmembrane tyrosine kinases includes the receptor for EGF (ErbB-1), two receptors for NDF/heregulin (ErbB-3 and ErbB-4) and an orphan receptor (ErbB-2). In order to examine the possibility that distinct signal transduction pathways are coupled to each ErbB protein, we examined the interaction of individual ligand-stimulated receptors with the c-Cbl protein, a protooncogene-encoded signaling molecule previously identified in hematopoietic cells. We report that c-Cbl undergoes rapid and sustained phosphorylation on tyrosine residues upon stimulation of fibroblast and epithelial cell lines with ligands of ErbB-1. By contrast, activation of either ErbB-3 or ErbB-4 by NDF did not affect tyrosine phosphorylation of c-Cbl. Likewise, activation of a chimeric ligand-stimulatable ErbB-2 by a heterologous ligand was ineffective. Despite rapidity of the EGF effect, we observed no association of c-Cbl with activated ErbB-1, implying that the interaction is indirect. Our in vitro experiments suggest that a candidate mediator of the interaction is the Grb-2/Ash adaptor protein, which is constitutively bound to c-Cbl. These results indicate that different ErbB proteins can couple to distinct signaling pathways, and therefore their physiological functions are probably non-redundant.
Animals↗
Synthetic vaccines for infectious and autoimmune diseases.
Explore the source record for details and available documents.
Animals↗