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Biomedical subjects

J G Michael

Publications and source records attributed to J G Michael.

At least 37 records · Page 2Linked to original sources
PubMed1991

Regulation of the human immune response to ragweed pollen by immunotherapy. A controlled trial comparing the effect of immunosuppressive peptic fragments of short ragweed with standard treatment.

A new allergenic preparation consisting of peptic fragments of short ragweed has been tested for its clinical effectiveness. Such enzymatically derived fragments have been shown in prior murine studies to retain the T epitopes of the original allergen but to have a severe reduction in the number of B epitopes. Three groups of ragweed hayfever patients were placed on pre-seasonal immunotherapy. One group received a conventional ragweed preparation that had been enriched for antigen E (Amb a I), designated as Pool 2. The second group was given fragments of Pool 2 (fSRW) prepared by peptic digestion and the third group was injected with histamine as a placebo. Groups treated with the fSRW and Pool 2 had significantly reduced symptom-medication scores compared with the placebo-treatment group. However, fSRW-treated patients fared significantly better than Pool 2 patients (P less than 0.02). fSRW injections caused a significant rise in preseasonal specific IgG, antibodies as well as suppression of the seasonal anamnestic specific IgE increase. Similar, but not quite as marked changes occurred with Pool 2 treatment. fSRW was well tolerated and non-toxic. Thus, allergen modification by enzymatic degradation, as demonstrated here, appears to be a promising new approach for allergen immunotherapy.

Adult↗
PubMed1990

Orally inducible immune unresponsiveness is abrogated by IFN-gamma treatment.

The role of murine epithelial cells from small intestine (IEC) in orally induced immune unresponsiveness has been investigated. Murine IEC were shown to express a relatively low level of class II MHC Ag and were incapable of presenting BSA to Ag-specific Th cells. IFN-gamma treatment of the animals dramatically enhanced expression of class II MHC Ag by IEC enabling Ag presentation to Th cells. Ag-presenting function of IEC after IFN-gamma treatment was not affected by IEC panning on anti-IgG or anti-MAC-1-coated plates but it was blocked by a class II MHC-specific mAb. IFN-gamma-treated mice were responsive to parenteral BSA challenge after oral administration of the Ag, whereas untreated mice were immunosuppressed. Our data support the concept that poor expression of class II MHC Ag on IEC contributes to immunosuppression induced by oral administration of a protein Ag.

Animals↗
PubMed1990

Cationization of protein antigens. V. Effect of the degree of cationization on patterns of immune responsiveness.

Preparations of bovine serum albumin (BSA) were cationized by substituting anionic side chain carboxyl groups with polycationic aminoethylamide groups. Different degrees of substitution were obtained by varying the reaction time. Mice immunized with partially cationized proteins produced early increased levels of antibody over those made by mice immunized with nBSA, followed by a period of decreased response before returning to a second period of enhanced and prolonged antibody synthesis. In contrast, fully substituted BSA gave rise to a significantly enhanced response which was delayed in its onset. Differences in isotype or in antibody specificity during the early and late periods of enhanced responsiveness could not be demonstrated. Cell transfer experiments showed that T cells harvested from mice immunized with the less cationized cBSA preparations could, in contrast to T cells from mice immunized with the fully cationized preparations, suppress antibody responses to both nBSA and cBSA in normal mice. These data are consistent with the possibility that the partially cationized proteins, in contrast to the fully cationized antigen, yield a unique pattern of responsiveness due to retention of determinants necessary for the induction of Ts while exhibiting the enhanced immunogenicity characteristic of cationized molecules.

Animals↗
PubMed1990

Modulation of the immune response to ragweed allergens by peptic fragments.

Fragments of short ragweed extract were prepared by peptic digestion and fractionated by molecular exclusion chromatography. We focused on fragmenting a ragweed fraction that was enriched for Amb aI. Digestion products in the molecular weight range of 5-15 kD (fSRW) were examined for their antigenic, immunogenic and immunosuppressive properties. fSRW was poorly immunogenic and unable to induce ragweed-specific PCA reactions in rat skin or to bind to anti-ragweed IgG antibodies. Intravenous administration of fSRW either prior to or after intraperitoneal immunization with a ragweed preparation resulted in a significant suppression of the immune response. T cells isolated from lymph nodes of mice immunized with ragweed were stimulated by fSRW in a lymphoproliferation assay. Moreover, T cells from mice injected with fSRW were immunosuppressive when transferred into mice immunized with intact ragweed antigens. Our data demonstrate that peptic fragments (fSRW) of ragweed lack B-cell determinants while retaining their T-cell immunoregulatory properties. Potentially these peptides are less likely to cause adverse reactions in allergen sensitive patients and thus offer a new approach to allergen immunotherapy.

Animals↗
PubMed1990

Modulation of the immune response to allergens: phospholipase A degradation products suppress IgG and IgE response in mice.

Degradation products of phospholipase A2 (PLA2), the major allergen of honeybee venom, were prepared by peptic digestion of the enzyme and fractionated by molecular exclusion chromatography. The largest of the isolated products, P-1, was found to be a centrally nicked PLA2 molecule with a loss of several amino acids. It was examined for its antigenic, immunogenic and immunosuppressive properties. This peptic product was unable to block antigen-antibody reactions between PLA2 and anti-PLA2 antibodies and was incapable of inducing passive cutaneous anaphylaxis in rat skin sensitized with mouse anti-PLA2 IgE antibodies. BDF1 female mice injected intravenously with P-1 exhibited suppressed IgG and IgE anti-PLA2 responses to a subsequent PLA2 immunization. Intravenous administration of P-1 to mice with ongoing immune response to PLA2 resulted in decline of antigen-specific IgE titers. Transfer of splenic T cells from mice injected with P-1 into naive recipients caused profound suppression of the response to subsequent immunization with PLA2 indicating presence of PLA2-specific T suppressor cells. These results indicate that a degradation product of PLA2 prepared by peptic digestion lost antigenic and immunogenic properties of the intact enzyme but retained immunosuppressive properties, thus offering a novel approach to allergen immunotherapy.

Allergens↗
PubMed1988

Cationization of protein antigens. IV. Increased antigen uptake by antigen-presenting cells.

Cationization of BSA generates a molecule that mounts antibody responses of increased magnitude and duration and induces T cell proliferation at concentrations 500 times less than native BSA (nBSA). To explain the alteration in immunogenic properties of this Ag, the uptake of nBSA and cationized BSA (cBSA) by splenic APC has been investigated. T cell proliferation assays were conducted with nBSA and cBSA preparations with varying degrees of substitution. An inverse correlation between the degree of cationization and the amounts of Ag needed for optimal T cell reactivity was observed. To determine whether affinity for APC resulted in an increased uptake of cBSA, splenic APC were incubated with nBSA or cBSA for varying amounts of time. Comparisons were made at each time point between untreated Ag-pulsed APC (Ag uptake) and paraformaldehyde-fixed Ag-pulsed APC (processed Ag). Proliferation of T cells primed with nBSA or cBSA increased in proportion to the amount of time of APC exposure to high concentrations of nBSA, first appearing after a 2-h pulse and peaking at 8 h. Conversely, untreated APC needed only a 30-min cBSA exposure to induce either nBSA- or cBSA-primed T cell proliferation, indicating a rapid uptake of cBSA. Comparisons with proliferation induced by paraformaldehyde-fixed cBSA APC indicate that nBSA T cells recognize a lag phase-processed form of cBSA, whereas a majority of cBSA T cells recognize either a rapidly processed form of cBSA, or a membrane-processed cBSA molecule without a classical lag phase processing event. When monensin was used as an inhibitor of fluid phase pinocytosis in splenic APC, the presentation of nBSA was inhibited by 85%, but the presentation of cBSA was inhibited by only 20%. These results imply that nBSA enters the cell by fluid phase pinocytosis, whereas cBSA enters by a nonspecific adsorptive mechanism. The different modes of cellular entry for the two molecules, nBSA and cBSA, resulting in a rapid uptake of cBSA, may have important ramifications on T cell activation and immunoregulation.

Animals↗
PubMed1988

Regulation of the immune response to allergens by immunosuppressive allergenic fragments. 1. Peptic fragments of honey bee venom phospholipase A2.

Nine patients with anaphylactic sensitivity to honey bee venom (HBV) were treated with P-1, a pepsin derived fragment of HBV phospholipase A2 (PLA2). P-1 caused only rare reactions with doses of 100 micrograms/injection. Treatment resulted in a substantial decrease in specific anti-PLA2 IgE and IgG antibodies as well as a decline in skin test sensitivity to PLA2. Another group of HBV-sensitive patients was treated with unaltered PLA2. Doses greater than 20 micrograms/injection were not tolerated. PLA2 injections caused an increase in anti-PLA2 IgG and IgE antibodies as well as increase in skin test sensitivity. This study demonstrates that a nonimmunogenic fragment derived from an allergen can downregulate immune responses and thus offer a new modality for therapy of allergic diseases.

Adult↗
PubMed1988

C3 dependent, C5 independent immune complex glomerulopathy in the mouse.

This study examines the role of complement in a murine model of accelerated nonproliferative immune complex glomerulopathy. Two C5 deficient strains (DBA/2J and B10.D2oSnJ) as well as normocomplementemic mice consistently develop heavy proteinuria and glomeruli show loss of normal visceral epithelial cell architecture within 4 days of intravenous antigen administration. In contrast, animals depleted of C3 with cobra venom factor fail to develop proteinuria and retain discrete foot processes. Semiquantitative evaluation of antigen and antibody in glomeruli shows equivalent deposition in mice from all groups. The localization of these deposits, however, is different in C3-depleted mice. There is extensive accumulation of deposits along the subepithelial aspect of the glomerular basement membrane of normocomplementemic and C5 deficient mice while deposits in glomeruli of C3-depleted animals accumulate in the subendothelial region and do not cross the glomerular basement membrane. These data demonstrate that in this model, glomerular injury is dependent on complement components generated up thru C3 but not C5 or latter components. In addition, our data suggest that C3 is important in the movement of immune complexes across the glomerular basement membrane. Although the mechanism by which complement is mediating injury in this model is not known, it does not appear to involve an inflammatory cell infiltrate or the terminal complement components.

Animals↗
PubMed1987

Cationization of protein antigens. III. Abrogation of oral tolerance.

The immunoregulatory effects of oral pretreatment of BDF1 mice with cationized bovine serum albumin (cBSA) and native bovine serum albumin (nBSA) have been compared. Oral administration of nBSA suppressed the antibody response to both forms of the antigen. In contrast, oral pretreatment with cBSA greatly enhanced the anti-BSA response in animals subsequently challenged i.p. with either the cationized or native form of the molecule. The enhancement observed with cBSA pretreatment was more pronounced than the suppression observed with the same amount and number of feedings of nBSA. As little as a single oral dose of 10 mg of cBSA produced a significant increase in antibody concentration. Cell transfer of spleen cells into irradiated syngeneic recipients demonstrated that both T cells and B cells were involved in the generation of the response, with a greater degree of enhancement provided by cBSA-pretreated T cells. These data extend our previous findings and demonstrate that administration of cBSA by a normally "tolerogenic" route results in enhancement rather than suppression of the immune response.

Administration, Oral↗
PubMed1987

Cationization of protein antigens. II. Alteration of regulatory properties.

Immunoregulatory effects of cationized bovine serum albumin (cBSA) and native bovine serum albumin (nBSA) have been investigated. Intravenous administration of nBSA to BDF1 mice substantially suppressed the antibody response to subsequent immunization with either nBSA or cBSA, whereas pretreatment with cBSA by the same route significantly enhanced the responses to both antigens. The functional properties of BSA-specific T and B cells from mice immunized with cBSA or nBSA were examined in reconstitution experiments in which splenic T populations together with B cells were transferred into irradiated syngeneic recipients. Transfer of splenic T cells from mice primed with nBSA caused profound suppression of the response to subsequent immunization with nBSA or cBSA, whereas transfer of either B or T cells from cBSA treated mice produced an enhanced response to both antigens. C57BL/6 mice, which are considered to be low responders to BSA, produced a significant antibody response to BSA when immunized with cBSA. In contrast, immunization with nBSA did not produce measureable amounts of antibody in mice of this strain. Our data clearly demonstrate that cationized BSA exhibits unique immunogenic properties due to alterations in the self-regulation of the immune response.

Adjuvants, Immunologic↗
PubMed1987

Idiotype regulation of the anti-bovine serum albumin response. I. Generation of an idiotype-specific Lyt-1-2+ suppressor T cell.

A monoclonal antibody (3C-7) specific for a determinant localized on the carboxy-terminus of the BSA molecule (P505-582) has been shown to cause suppression of the multispecific BSA antibody response if given i.v. before immunization. The fine binding specificity and the isotype subclass are not responsible for the suppression generated. Administration of 3C-7 i.v. results in the generation of a suppressor T cell that, when transferred into reconstituted irradiated mice, results in a diminished anti-BSA response. Suppression can be eliminated by panning T cells on idiotype (3C-7) coated plates, but not by panning on BSA, polyclonal anti-BSA antibodies, or MOPC 21. The action of the cell is antigen (BSA) specific. Idiotype-binding T cells reconstitute suppression and appear to be Lyt-1-2+. These observations demonstrate that a limited set of monoclonal antibodies directed against a single determinant on a protein molecule have the capacity to regulate the immune response to a multiplicity of determinants present on the same protein. These data support the concept of antibody-induced regulation by the induction of suppressor cells through idiotype recognition.

Animals↗
PubMed1987

Cationization of protein antigens. I. Alteration of immunogenic properties.

We have shown that a cationized form of bovine serum albumin (BSA) produced by substituting anionic side chain carboxylic groups with aminoethylamide groups possesses unique immunologic properties. The two forms of antigen, native (nBSA) and cationized (cBSA), cross-react at the level of the B cell, as evidenced by the ability of antibody raised against one form to react with the other and by inhibition assays using ELISA. T cell cross-reactivity was also observed in proliferation assays, but the amount of cBSA required for stimulation was 500 times less than the amount of native protein needed. In vivo, cBSA produced responses which, at their optimal levels, were at least double the response to nBSA and which showed a different kinetic pattern, peaking later and lasting longer than the response to the native molecule. Moreover, antibodies were produced in response to administration of cBSA but not nBSA when given i.v. in saline, without an adjuvant. Although a mechanism for these phenomena is not yet clear, we speculate that the cBSA may have a greater affinity for antigen-presenting cells or for the T cell receptor, or that the altered structure may enhance recognition of the molecule by APC and/or helper T cells.

Animals↗
PubMed1987

Peptic fragments of bovine serum albumin bind antigen-specific T suppressor cells from orally tolerized mice.

The antigenic structures capable of binding immunoregulatory T cells have been investigated. The functional properties (suppression or help) of BSA-specific T cells from primed or orally tolerized mice with capacity to adhere to bovine serum albumin or its peptic fragments were examined in reconstitution experiments in which splenic T-cell populations together with naive B cells were transferred into irradiated syngeneic recipients. Antigen-specific T suppressor cells isolated from mice tolerized to BSA adhered to peptic fragments of BSA as well as to the intact antigen. BSA-specific T helper cells adhered only to the intact antigen. Our data suggest that the preferential activation of T suppressor cells following administration of peptic fragments may be due to their ability to adhere to such fragments. These findings offer a novel approach of separation and identification of T suppressor cells and may be useful in further studies of immunosuppression.

Administration, Oral↗
PubMed1987

An immune complex glomerulopathy associated with glomerular capillary thrombosis in the laboratory mouse. A highly reproducible accelerated model utilizing cationized antigen.

An accelerated, highly reproducible model of an immune complex glomerulopathy in the laboratory mouse was developed by using cationized bovine gamma-globulin (cat-BGG) as the nephritogenic agent. Preimmunized Balb/c mice given three 250-micrograms doses of cat-BGG consistently develop a nonproliferative glomerular lesion which becomes manifested clinically by the nephrotic syndrome and results in death within 14 days. Significant proteinuria is evident by day 4 (24 hours after the third dose of cat-BGG) at which time extensive deposits of cat-BGG, IgG, and C3 are localized along the glomerular capillary walls. At the ultrastructural level, subepithelial deposits and foot process effacement are evident. By day 6, subendothelial and mesangial deposits are also present, and by day 10, extensive glomerular capillary thrombosis and early crescent formation develop. The reproducibility and rapidity of the induction of disease, and the spectrum of pathological changes occurring in the glomeruli make this murine model of an immune complex glomerulopathy potentially useful for the study of the mechanisms underlying the induction and progression of glomerular injury and the evaluation of potential therapy.

Animals↗
PubMed1986

Cationic antigens. Problems associated with measurement by ELISA.

The measurement of the mouse antibody response to cationized bovine serum albumin (cat BSA) and bovine gammaglobulin (cat BGG) was complicated because of the unique properties of these antigens. Cat BGG non-specifically bound rabbit anti-mouse gammaglobulin conjugated to alkaline phosphatase. This was minimized by adding the polyanion, heparin. Cat BSA also reacted non-specifically with some conjugates, but the reaction with specific antibody was enhanced by the addition of the polyanions heparin or dextran sulfate. The non-specific reaction did not appear to be related to the concentration of antigen used to coat the plastic plates. In addition, in ELISA inhibition experiments high concentration of antigens (greater than 100 micrograms/ml) seemed to result in non-specific inhibition of the antibody antigen reaction. A proposed model to explain the problems is based on the polycationic surface formed by coating the plates with the cationized proteins. This cationic surface can be neutralized by polyanions, reducing the non-specific and enhancing the specific reactions. It appears that other polycationic molecules might share these unique properties and these factors must be considered when they are measured.

Alkaline Phosphatase↗
PubMed1984

Analysis of humoral and cellular factors that contribute to impaired immune responsiveness in experimental uremia.

An experimental model in rats was developed to define the nature of humoral and cellular factors that contribute to impaired immune responsiveness in chronic renal failure. Addition of uremic rat serum to both normal and uremic lymphocytes significantly suppressed cellular responses, the suppression being more pronounced with uremic lymphocytes. Lymphocytes from uremic rats were only marginally less responsive than normal lymphocytes to concanavalin A stimulation when normal rat serum was added to the cultures, indicating that the cellular factors in impairment were less important than humoral ones. Antibody formation in rat splenocyte cultures to bovine serum albumin was suppressed by addition of uremic serum, but the response to sheep erythrocytes was unaffected. Thus the effect on antibody response in uremic animals is dependent upon the antigen tested.

Animals↗
PubMed1984

Kinetics of oral tolerance: study of variables affecting tolerance induced by oral administration of antigen.

The induction of antigen-specific tolerance by oral administration of hen egg albumin (OVA) was shown to be time- and dose-dependent. The IgE response was the most effectively suppressed by antigen feeding prior to or after parenteral immunization. The effect on IgG response paralleled that observed on the IgE response, but the magnitude of suppression was less pronounced. The IgA response was enhanced rather than suppressed if the interval between feeding and parenteral immunization was short or if the animals were antigen-fed after the intraperitoneal priming.

Administration, Oral↗