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Biomedical subjects

A H Sehon

Publications and source records attributed to A H Sehon.

At least 73 records · Page 4Linked to original sources
PubMed1984

Studies on the mechanism of suppression of experimental allergic encephalomyelitis induced by myelin basic protein-cell conjugates.

The mechanism of suppression of experimental allergic encephalomyelitis (EAE) induced in Lewis rats by pretreatment with myelin basic protein (MBP) coupled to syngeneic spleen leukocytes (SL) was examined. Studies on the kinetics of the tolerance induction showed that pretreatment with MBP-SL suppressed EAE if given 7 but not 3 days before the disease-inducing injection of MBP in Freund's complete adjuvant. Treatment with cyclophosphamide 48 hr before administration of MBP-SL completely abolished the suppression of EAE. Transfer of lymph node and spleen cells from MBP-syngeneic erythrocyte conjugate (MBP-RBC) but not MBP-SL-pretreated rats resulted in suppression of disease in recipients subsequently given a disease-inducing injection of MBP. Administration of MBP coupled to SL from the histocompatible rat strain F344 resulted in suppression of the MBP-induced proliferative response of spleen cells from Lewis rats which had been given a disease-inducing injection of MBP. Taken together these results are consistent with the suppression of EAE induced by MBP-SL being mediated by suppressor T cells.

Animals↗
PubMed1984

Determinants of ryegrass pollen cytochrome c recognized by human IgE and murine monoclonal antibodies.

In attempts to produce fragments of an allergenic molecule which would retain allergenic and/or antigenic determinant(s), the cytochrome c of ryegrass (RG) pollen, which had been shown to be an allergenic constituent of this pollen, was digested with trypsin and chymotrypsin and the resulting fragments were separated by high performance liquid chromatography. Several of these fragments were shown, with the aid of the radioallergosorbent test and solid phase radioimmunoassays, to bind IgE antibodies present in a pool of six sera from grass-sensitive patients and three murine monoclonal antibodies, designated as Mab 41, Mab 42 and Mab 43, which had been originally produced against the crossreacting cytochrome c of Kentucky bluegrass (KBG). In summary, (i) fragments C-67 and C-74 reacted with all antibodies, (ii) fragments T-45, T-46 and C-69 bound to human IgE antibodies as well as to Mab 41 and Mab 42, but not to Mab 43, (iii) fragment T-44 reacted only with Mab 41 and Mab 42, and (iv) fragment C-83 bound only Mab 42 and Mab 43. On the basis of these results, it is concluded that (i) immunochemically active fragments of the RG cytochrome c can be readily produced by enzymatic degradation, (ii) there is significant crossreaction between the antigenic determinants of RG and KBG cytochromes c, (iii) whereas all fragments possessed at least two of the original antigenic determinants, fragments C-83 and T-44 were devoid of allergenic determinants, (iv) the antigenic determinants recognized by Mab 41 and Mab 42 were different from those reacting with human IgE antibodies and Mab 43, (v) each of the three monoclonal antibodies recognized a distinct antigenic determinant, (vi) fragments C-67 and C-74 possessed all determinants recognized by the human IgE and mouse antibodies used.

Animals↗
PubMed1984

Immunoregulatory function of human cord blood lymphocytes on immunoglobulin production.

The functional maturity of human umbilical cord blood B lymphocytes and the immunoregulatory activity of cord T lymphocytes were assessed by measuring the in vitro immunoglobulin production by B cells from either cord or adult blood. Supernatants from 48-hr pokeweed-mitogen (PWM) stimulated cord or adult lymphocyte cultures were added to cord or adult B cell cultures in the presence of PWM; a significant amount of immunoglobulin was produced in adult B cell cultures only. Adult B or T cells were then cocultured with cord T or B cells; a significant amount of immunoglobulin was again found only in adult B cell cultures. These results indicated that cord B cells were functionally immature and that cord helper T cell function was adequate but masked by excessive suppressor activity. Indeed, addition of cord T cells but not of allogeneic adult T cells to PWM stimulated adult lymphocyte cultures inhibited their immunoglobulin production; this confirmed cord T cells' increased suppressor activity. Cord T cells were not intrinsically suppressive since they failed to suppress immunoglobulin production by Epstein-Barr Virus (EBV) transformed B cells. They could be activated, however, by PWM or allogeneic cells (in mixed lymphocyte cultures) and their effect was mediated via soluble factor(s) as demonstrated by the suppressor effect of these culture supernatants on immunoglobulin production by unfractionated adult lymphocytes. In contrast, when these supernatants were added to T cell-depleted adult lymphocyte cultures, enhancement rather than suppression was observed. These results indicated that the soluble factor(s) released by Cord T lymphocytes was not suppressing per se but induced suppression through activation of suppressor cells.

Adult↗
PubMed1984

In vitro synthesis of IgE by human lymphocytes. III. IgE-potentiating activity of culture supernatants from Epstein-Barr virus (EBV) transformed B cells.

Seven Epstein--Barr virus (EBV)-transformed B cell lines were derived from circulating lymphocytes of two atopic and two non-atopic individuals, two preparations of cord blood lymphocytes and one tonsillar lymphocyte preparation. All the cell lines contained a significant proportion of cells expressing Fc epsilon R as detected by rosette formation with IgE-coated bovine erythrocytes (E-IgE) and by flow cytometry using IgE-linked to fluorescent microspheres. None of the cell lines displayed FcR for IgA, IgM or IgG. The cell-free supernatants (CFS) of EBV-transformed cells contained IgE-binding factors (IgE-BFs) detected by their ability to inhibit the binding to RPMI 8866 cells of either E-IgE or IgE-linked to microspheres. Whereas these CFS enhanced the synthesis of IgE and suppressed the synthesis of IgG by purified B lymphocytes isolated from the blood of allergic donors and cultured in the absence of stimulant, their effect on the synthesis of IgA or IgM was not predictable. CFS significantly enhanced the secretion of IgE by the U266 myeloma cell line without interfering with secretion of IgM, IgG or IgA by EBV-transformed cells. These data are in accord with similar properties of RPMI 8866 cells and suggest that B lymphocytes might play a regulating role in the IgE synthesis.

B-Lymphocytes↗
PubMed1984

The suppression of insulin-specific immune responses by the administration of insulin-derivatized syngeneic cells and soluble lysates from these cells.

The results of this study demonstrated that the i.v. administration of insulin, in the form of a conjugate with either syngeneic spleen cells (SC) or peritoneal exudate cells (PEC), markedly reduced the capacity of recipient mice to develop insulin-specific immune responses, as manifested by diminished in vivo IgE antibody production and by depressed in vitro, lymph node cell proliferation responses, respectively. Furthermore, it was shown that i.v. injection of insulin-PEC conjugates induced the activation of suppressor cells that had the capacity to downregulate insulin-specific IgG plaque-forming cell (PFC) responses. Finally, it was also determined that freezing and thawing of the insulin-PEC conjugates resulted in the release of a soluble tolerogenic molecule and/or membrane preparation that could also markedly depress insulin-specific IgG antibody production.

Animals↗
PubMed1984

Demonstration of auto-anti-idiotypic antibody cross-reacting with public idiotypic determinants in the serum of rye-sensitive allergic patients.

The present study documents the presence, in the serum of one allergic individual, of auto-anti-idiotypic antibodies cross-reacting with public idiotypic determinants expressed on human IgE and IgG anti-Rye I antibodies. Sera from rye-sensitive patients were tested for specific IgG and IgE antibodies to Rye I by double antibody. The IgG fraction, isolated from the serum of a patient with a history of previous hyposensitization therapy, was repeatedly absorbed on Rye-I-Sepharose as well as on IgM- and IgG-Sepharose to remove anti-Rye I antibodies as well as any possible anti-heavy or light chain activity. This IgG fraction, named anti-idiotypic fraction (a-IdF), blocked in a dose-dependent fashion the reaction of IgG and IgE anti-Rye I antibodies with Rye I antigen. The a-IdF also blocked the binding of anti-rye antibodies to Rye I antigen in the serum of 20 unrelated allergic patients, indicating that these anti-Rye I antibodies bore public idiotypic determinants.

Adolescent↗
PubMed1984

Immunochemical properties of some monoclonal IgE antibodies to 4-hydroxy-3-nitrophenylacetyl (NP).

Several hybridoma cell lines secreting NP-specific, murine IgE antibodies were generated by fusion of P3-X20 (gamma, kappa) tumour cells with spleen cells from (BALB/c X C57B1/6)F1 (CB6F1) mice previously immunized with NP-ovalbumin. Four subclones (designated NP-epsilon-3.57, NP-epsilon-15.88, NP-epsilon-91.58 and NP-epsilon-95.31) were propagated in vivo and milligram quantities of the corresponding IgE antibodies were purified from ascitic fluid by gel filtration, ion exchange chromatography and affinity chromatography. Immunological analyses and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) indicated that NP-epsilon-15.88, NP-epsilon-91.58 and NP-epsilon-95.31 all possessed lambda 1 (or possibly lambda 3) light chains; and that NP-epsilon-3.57 possessed lambda 2 light chains; NP-epsilon-95.31 also expressed the P3-X20 derived, MOPC-21 kappa light chain. Radioallergosorbent test (RAST) titration curves, generated from the interaction of the four monoclonal IgE antibodies with NP-BSA attached to paper discs (NP-BSA-P) were found to be non-overlapping. Measurements of the relative amounts of NP-epsilon-aminocaproic acid (NP-CAP) and 4-hydro-3-iodo-5-nitrophenylacetyl-epsilon-aminocaproic acid (NIP-CAP) that were required to inhibit by 50% the binding of the 4 IgE antibodies to NP-BSA-P indicated that these antibodies were all heteroclitic, since their affinity for NIP appeared to be higher than their affinity for NP. These results, in conjunction with other findings reported in the literature, suggested that the V regions of NP-specific IgE antibodies are similar to the V regions of NP-specific IgM and IgG antibodies, produced by the same mouse strains. Finally, in vitro histamine release measurements demonstrated that two of these monoclonal IgE antibodies could mediate antigen induced histamine release from passively sensitized rat peritoneal mast cells.

Animals↗
PubMed1984

In vitro synthesis of IgE by human lymphocytes. II. Enhancement of the spontaneous IgE synthesis by IgE-binding factors secreted by RPMI 8866 lymphoblastoid B cells.

RPMI 8866 lymphoblastoid cells, known to express surface Fc epsilon R, were tested for their ability to regulate the in vitro synthesis of human IgE. Cell-free supernatants (CFS) of RPMI 8866 cells enhanced in a dose-dependent fashion the spontaneous IgE synthesis by B cells of allergic individuals. For maximum activity the CFS had to be added during the first 3 days of culture. CFS did not significantly alter the spontaneous synthesis of IgM or IgG, but they suppressed IgA synthesis both in B cell cultures and in pokeweed mitogen-stimulated peripheral blood mononuclear cells cultures. Cyclosporin A did not suppress either the spontaneous Ig production by B cells nor the IgE-potentiating activity of CFS. The enhancing activity of CFS was related to its content in IgE binding factors (IgE-BFs); these factors were detected by their ability to inhibit the rosetting of RPMI 8866 cells with IgE-coated erythrocytes (E-IgE). Both the IgE-BFs and the IgE-potentiating activity of the supernatants of RPMI 8866 cell cultures could be removed by absorption with IgE-Sepharose, from which they could subsequently be eluted with glycine-HCl buffer. IgE-BFs were identified as glycoproteins on the basis of their sensitivity to trypsin and to neuraminidase. By filtration of the RPMI 8866 cell supernatants through a Sephadex G75 column, IgE-binding activity was found to be associated with two fractions with molecular sizes in the range of 10,000-15,000 and 30,000-40,000. The IgA-suppressing activity of the RPMI 8866 culture filtrates could be absorbed with sIgA-Sepharose from which it was subsequently recovered by elution with glycine-HCl buffer. Most unexpectedly, sIgA-Sepharose also removed IgE-BFs and IgE-potentiating activity from the RPMI 8866 supernatants; both could be recovered by subsequent elution from sIgA-Sepharose with gycline-HCl buffer. These data are provisionally interpreted as indicating that the IgE-BFs secreted by RPMI 8866 cells had affinity for both IgE and sIgA and that they exerted a reciprocal effect on the in vitro synthesis of IgE and IgA.

B-Lymphocytes↗
PubMed1984

In vitro synthesis of IgE by human lymphocytes. IV. Suppression of the spontaneous IgE synthesis by IgE-binding factors secreted by tunicamycin-treated RPMI 8866 cells.

It was previously shown that RPMI 8866 cells released IgE-binding factors (IgE-BFs) capable of enhancing the spontaneous in vitro synthesis of IgE by purified B lymphocytes isolated from allergic individuals. In the present study, the influence of tunicamycin, an inhibitor of protein glycosylation, on RPMI 8866 cells was investigated with regard to: (i) the expression of surface receptors for IgE; (ii) the release of IgE-BFs into the culture supernatants, and (iii) the biological activity of IgE-BFs. After preincubation for 60 min with tunicamycin (1 microgram/ml), RPMI 8866 cells were cultured for 48 hr in HB 101 serum-free medium; the culture supernatant was then filtered, concentrated, and its biological activity was compared to that of a parallel culture supernatant from untreated RPMI 8866 cells. The results of these experiments indicate that exposure of RPMI 8866 cells to tunicamycin resulted in: (i) a reduction of surface Fc epsilon R; (ii) no effect on the release of IgE-BFs into the culture supernatant, and (iii) the conversion of IgE-potentiating factors into IgE-suppressing factors. The latter factors suppressed the IgE secretion by U266 myeloma cells and completely inhibited the activity of IgE-potentiating factors on B lymphocytes from allergic individuals. IgE-BFs secreted by tunicamycin-treated cells had no effect on the production of IgG, IgA or IgM by normal or EBV-transformed B cells.

Antibodies, Neoplasm↗
PubMed1984

In vitro synthesis of IgE by human lymphocytes. I. The spontaneous secretion of IgE by B lymphocytes from allergic individuals: a model to investigate the regulation of human IgE synthesis.

In view of the controversial data in the literature regarding the in vitro IgE synthesis by human lymphocytes, the conditions for culture of lymphocytes and the methodology for measurement of the IgE produced are described in detail. In the absence of any added mitogen, enriched B cell preparations derived from 70% of allergic donors actively secreted 100 to 3200 pg/ml of IgE after culture for 7 days, at which time the cell viability was higher than 85%. In comparable B cell cultures derived from non-allergic donors, only trace amounts of de novo synthesized IgE were detected in 20% of the cases. All B cell cultures actively secreted IgG, IgA, IgM and there was no apparent relationship between the secretion of IgE and that of the other classes of Ig. By contrast, the synthesis of IgE by unfractionated peripheral blood mononuclear cells of allergic individuals, which were stimulated with pokeweed mitogen (PWM) under several experimental conditions, was not consistently reproducible, i.e. the spontaneous synthesis of IgE in such cultures was either suppressed or enhanced by PWM. The most important finding was that the secretion of IgE was selectively enhanced by supplementing the B cell cultures with cell-free supernatants (CFS) of cultures of neonatal lymphocytes which had been preincubated with 10 micrograms/ml IgE. It is, therefore, concluded that B cell cultures from allergic individuals constitute an appropriate model for investigations of the mechanisms underlying the regulation of human IgE synthesis.

Adult↗
PubMed1984

Suppression of the anti-trimellityl (TM) IgE response in mice by conjugates of TM with polyvinyl alcohol.

The i.p. injection of 1 microgram of TM3-OA or TM9-OA with 1 mg of A1(OH)3 into B6D2F1 mice elicited the production of antibodies of the IgE and other classes to the trimellityl (TM) group and ovalbumin (OA). The induction of anti-TM antibodies belonging to the IgE and other immunoglobulin classes was specifically suppressed by the administration of tolerogenic conjugates prepared by coupling trimellitic anhydride (TMA) to the hydrophilic non-immunogenic polymer, polyvinyl alcohol (PVA), prior to immunization with TM-OA conjugates. More importantly, established anti-TM responses were also suppressed by these TM-PVA conjugates. By contrast, however, treatment with TM-PVA conjugates did not affect either the primary or the established anti-OA antibody response. The tolerogenic effects of the PVA conjugates were dose-dependent and appeared also to be dependent on the epitope density. Treatment with these conjugates also prevented immunized mice from showing any symptoms of systemic anaphylaxis on challenge with polyvalent TM-protein conjugates. These findings indicate that these conjugates may have the potential of useful therapeutic agents for the treatment of TMA-induced pulmonary hypersensitivity diseases.

Anaphylaxis↗
PubMed1983

The suppression of experimental allergic encephalomyelitis in Lewis rats by treatment with myelin basic protein-cell conjugates.

Pretreatment of Lewis rats with guinea pig (GP) myelin basic protein (MBP) coupled to syngeneic spleen leukocytes (SL) suppressed the subsequent induction of experimental allegic encephalomyelitis (EAE) with GP-MBP in Freund's complete adjuvant. The degree of suppression correlated positively with the amount of antigen coupled to the SL. GP-MBP coupled to syngeneic red blood cells (RBC) also resulted in suppression of EAE and the extent of the suppression was related to the dose of cells. These regimens of pretreatment also resulted in a decrease in the in vitro lymphocyte proliferative response to GP-MBP and in the extent of perivascular cuffing in the spinal cord. No decrease in the anti-MBP antibody response was detected in rats pretreated with either GP-MBP-SL or GP-MBP-RBC conjugates. Transfer of lymph node cells from rats pretreated with GP-MBP-RBC resulted in a decrease in disease severity in recipients. It is concluded that prior administration of MBP-cell conjugates is an effective way of suppressing the symptoms of EAE.

Animals↗
PubMed1983

Tumor-reactive IgE antibodies in plasma of patients with gastrointestinal carcinomas.

A total of 208 plasma samples from 115 patients with gastrointestinal carcinomas and nine patients with other intestinal disease were examined for the presence of IgE tumor antibodies by a solid-phase radioimmunoassay. Approximately one-third of the patients gave significant reactions with gastrointestinal carcinoma extracts compared with normal tissue extracts. Absorption with tumor and normal tissue extracts, with type AB human red cells, and with CEA indicated tumor specificity in some of the samples so examined. None of the 50 serum samples tested from normal blood donors contained tumor-specific IgE. IgE tumor antibodies decreased or completely disappeared in the majority of patients 8-13 days after surgical treatment.

Antibodies, Neoplasm↗
PubMed1983

Immunochemical characterization of a high molecular weight basic allergen (HMBA) of rye grass (Lolium perenne) pollen.

A high molecular weight basic allergen (HMBA) was isolated from the mixture of non-dialysable components of the aqueous extract of defatted rye grass pollen by a combination of gel filtration and isoelectrofocusing, HMBA, a glycoprotein of mol. wt 56,800 (17% carbohydrate) contained all naturally occurring amino acids. A hyperimmune rabbit anti-HMBA serum gave only a single precipitin band with the crude extract of the rye grass pollen in crossed immunoelectrophoresis. Thus, it was concluded that HMBA was a unique and highly purified antigen. The allergenicity of HMBA was revealed by its ability to elicit immediate skin reactions in grass allergic patients. Moreover, all patients' sera tested had IgE antibodies to HMBA detectable by direct RAST with HMBA allergosorbent discs. These observations indicated that HMBA was a major allergenic constituent of rye grass pollen. Treatment of HMBA by 6 M guanidine HCl led to a significant reduction in its ability to combine with human IgE antibodies. The treatment also resulted in the complete loss of allergenicity (i.e. inability to elicit PCA reactions with a murine reaginic antiserum to HMBA) and antigenicity (inability to form precipitins with rabbit anti-HMBA); hence, it would appear that the allergenic and antigenic determinants of HMBA are 'conformational'.

Amino Acids↗
PubMed1983

Direct action of cyclosporin A on human B-lymphocytes with regard to immunoglobulin production.

Highly purified preparations of human B-lymphocytes were cultured with or without cyclosporin A (CyA; 1 microgram/ml) for 8 days with pokeweed mitogen (PWM) in the presence of helper factors or with Epstein-Barr virus (EBV). The amounts of IgG, IgM, IgA and IgE produced in cultures were measured by radioimmunoassays or by reverse hemolytic plaque-forming cell assays. The results demonstrate that whereas CyA had a strong suppressive effect on the production of immunoglobulins (Ig) by PWM-activated B-cells, it had an enhancing effect on EBV-activated B-cells. It is concluded that CyA has a direct effect on human B-lymphocytes and that it may suppress or enhance their activation depending on the stimulant employed to trigger the cells.

B-Lymphocytes↗
PubMed1982

Allergenic cross-reactivity of cytochromes c of Kentucky bluegrass and perennial ryegrass pollens.

The allergenic cross-reactivity of cytochromes c isolated from Kentucky bluegrass (KBG) and ryegrass (RG) pollens was demonstrated by the finding that both cytochromes elicited PCA reactions of comparable titers in rats sensitized with murine reaginic antiserum to either KBG or RG cytochrome c. However, allergenic differences were revealed at limiting doses of the cytochromes c; under these conditions RG cytochrome c elicited PCA reactions only with the homologous reaginic serum, whereas KBG cytochrome c elicited PCA reactions with both murine reaginic sera. Moreover, in experiments involving inhibition of PCA, RG cytochrome c failed to neutralize some of the IgE antibodies of the antiserum to KBG cytochrome c, whereas KBG cytochrome c neutralized all IgE antibodies of both murine reaginic antisera. From these results it may be concluded that: (1) the two cytochromes c share common allergenic determinants, and (2) the KBG cytochrome c possesses additional allergenic determinant(s) not present on RG cytochrome c. The radioallergosorbent test, utilizing KBG cytochrome c discs and a pool of sera of individuals allergic to KBG, was inhibited to the extent of 87 or 41% by the addition of 10 micrograms of KBG or RG cytochrome c, respectively. By contrast both cytochromes c at 10 micrograms were equally effective in the inhibition (92%) of the binding of the IgE antibodies in this serum pool to RG cytochrome c allergosorbent discs. These experiments confirmed that the two cytochromes share common allergenic determinants.

Amino Acids↗
PubMed1982

Suppression of IgE antibodies with conjugates of haptens or allergens and synthetic hydrophilic polymers.

A variety of allergens and allergenic haptens can be converted to nonimmunologenic and tolerogenic derivatives by conjugation to nonimmunogenic, hydrophilic, synthetic polymers, such as mPEG, PVA, and PVP. The resulting conjugates of common allergens and of small molecules, such as those responsible for drug allergies, can potentially be used therapeutically for the specific suppression of the IgE antibodies that mediate the corresponding allergic manifestations of the immediate type. All these conjugates exert their immunosuppressive effect in mice by activating suppressor T cells; hapten-PVA and hapten-PVP conjugates--as distinct from antigen-mPEG conjugates--also appear to inactive the hapten-specific B cell population.

Allergens↗