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Biomedical subjects

G H Strejan

Publications and source records attributed to G H Strejan.

At least 37 records · Page 2Linked to original sources
PubMed1987

Antigen leakage from immunosorbents. Implications for the detection of site-directed auto-anti-idiotypic antibodies.

The detection of site-directed anti-idiotypic antibodies is usually based on their ability to inhibit the binding of antigen to idiotype, in either solid- or fluid-phase radioimmunoassays. Passage of serum over antigen-coupled immunosorbents for the purpose of removing the idiotypes from complexes with putative anti-idiotypic antibodies resulted in the release of significant amounts of antigen into the effluents. Normal sera or even isotonic buffers were similarly contaminated with antigen. The amount of antigen released ranged between 200-400 ng/ml, well in excess of the minimal amount required in the inhibition assay. Antigen was detected in effluents passed over a number of antigen coupled-matrices and even in affinity-purified antibody preparations obtained by elution from immunosorbents coupled with dinitrophenyl (DNP)-protein conjugates. Attempts to stabilize the antigen-coupled matrices with glutaraldehyde resulted in a perceptible but insufficient decrease in the amount of antigen released. In the case of anti-hapten antibodies, antigen interference was circumvented by utilizing monovalent haptens such as DNP-lysine coupled to the immunosorbent either directly or through a spacer arm. In the case of protein antigens, the leakage was almost completely prevented by preparing glutaraldehyde-polymerized immunosorbents directly from solution.

Animals↗
PubMed1986

The role of myelin lipids in experimental allergic encephalomyelitis. III. Transfer of suppression from guinea pigs recovering from EAE, induced by myelin basic protein--galactocerebroside complexes.

Juvenile strain 13 guinea pigs were immunized with myelin basic protein (MBP) combined with galactocerebrosides (MBP + GC) or with total myelin lipids without GC [MBP + (TL-GC)] in CFA. Control animals received dinitrophenylated-ovalbumin (DNP-OA) in CFA, CFA or IFA alone. The animals injected with MBP + GC showed a higher rate of recovery from the first EAE episode (83%) than those treated with MBP + (TL-GC) (50%). With the exception of the group treated with IFA alone, all animals were refractory to EAE following rechallenge with MBP in CFA 90 days after the first exposure. The in vitro proliferative response to MBP, of peripheral blood lymphocytes (PBLs) derived from guinea pigs freshly sensitized to MBP in CFA, was drastically suppressed in the presence of PBLs from animals injected with MBP + GC. Upon transfer to normal syngeneic recipients, spleen cells from MBP + GC-treated animals completely suppressed the clinical and histological manifestations of EAE following recipient challenge with MBP in CFA. Cell-free supernatants from PBLs and spleen cells of strain 13 guinea pigs treated with MBP + GC inhibited lymphocyte proliferation to MBP, of allogeneic responder cells, and spleen cell supernatants completely suppressed the induction of EAE upon transfer to allogeneic recipients. Suppression could not be transferred with cells from other treated groups. These results suggest that animals immunized with MBP + galactocerebrosides in CFA develop suppressor cells that may be in part responsible for the recovery from the first EAE episode and for protection against rechallenge with MBP in CFA. Their cell-free supernatants act in an MHC-nonrestricted fashion. These results do not rule out an additional protective mechanism since all animals exposed to CFA were refractory to rechallenge despite lack of demonstrable suppressor cell activity.

Animals↗
PubMed1986

The role of myelin lipids in experimental allergic encephalomyelitis. Part 2. Influence on disease production by encephalitogenic doses of myelin basic protein.

Hartley guinea pig CNS myelin lipids (TL) were combined with an encephalitogenic dose (50 micrograms) of myelin basic protein (MBP) and injected together with complete Freund's adjuvant (CFA) into juvenile strain 13 guinea pigs. All the animals developed acute EAE and recovered, but only 50% had a single mild relapse during an observation period of 12 months. To determine the effect of individual myelin lipids on EAE, purified fractions comprising the galactocerebrosides (GC) or gangliosides (GANG) were combined with 50 micrograms MBP together with phosphatidyl choline (PC) and cholesterol (CHOL) and injected with CFA into juvenile Hartley guinea pigs. Control animals received MBP mixed with PC and CHOL or MBP alone, in CFA. The incidence of acute EAE was similar in all groups, but the highest percent recovery (69%) was seen in animals immunized with the MBP-GC combination. All animals that developed acute EAE in the control groups died. Histologically, CNS myelin breakdown was present during the acute attack except in the MBP control group. Parameters of cell-mediated immunity (CMI) showed good correlation with the clinicopathological findings in animals that received MBP-GC or MBP alone. In most animals, serum anti-MBP antibodies were detected as early as 10 days post-immunization (p.i.) whereas anti-lipid antibodies were found at 90 days p.i. Animals that received MBP-PC did not show any positive CMI or serum antibodies although they developed severe disease. The results indicate that myelin lipids, especially the galactocerebrosides, contribute to the development of chronic EAE; however, the mechanism by which this occurs is still obscure.

Animals↗
PubMed1985

Antigen- and isotype-specific regulation of IgE responses by Lyt 1+,2,3- and Lyt 1-,2,3+ T suppressor cells.

Antigen-specific, IgE isotype-selective suppression is induced following treatment of mice with a high-molecular-weight glutaraldehyde-polymerized ovalbumin preparation (OA-POL). The results show that the suppression is mediated by Lyt 1+,2,3- cells residing in the spleen. Adoptive transfer experiments indicate that Lyt 2,3+ or Lyt 1,2,3+ cells are not required for the establishment of suppression by these Lyt 1+,2,3- suppressor T cells (Ts). Treatment of OA-POL-induced Ts cells with anti-I-Jk serum and complement does not affect their ability to suppress. In marked contrast, spleen cells from animals treated with a single course of OA-POL almost 300 days previously, were shown to contain boosterable memory suppressor T cells (Tsm) which display the Lyt 1-,2,3+ phenotype. The activity of both Ts and Tsm cells appears to result from stimulation by determinants common to native OA and OA-POL rather than by idiotypic determinants expressed on anti-OA antibodies.

Animals↗
PubMed1984

Suppression of experimental allergic encephalomyelitis in Lewis rats treated with myelin basic protein-liposome complexes: clinical, histopathological, and cell-mediated immunity correlates.

Guinea pig myelin basic protein (MBP) was inserted into phosphatidylserine liposomes and Lewis rats were injected by the intracardiac (ic) route with 75 microgram doses of MBP-liposomes according to various schedules. After challenge with 75 microgram guinea pig MBP in complete Freund's adjuvant, the rats were followed for clinical signs, were tested for delayed hypersensitivity (DTH) and lymphocyte transformation (LT) to MBP. The animals were sacrificed 30 days after challenge and the central nervous system tissue was examined for histological modifications. Rats treated with two injections of MBP-liposomes, 7 days before and 7 days after challenge, showed the highest degree of protection from clinical manifestations. Histological lesions were not significantly reduced. DTH reactions to MBP were all positive, regardless of treatment. LT assays were positive overall in only 50% of the animals tested. The response to rat MBP was significantly lower than to guinea pig MBP, especially in the groups treated with MBP-liposomes. Adoptive transfer of spleen cells from MBP-liposome-treated donors reduced the clinical scores of actively induced EAE in syngeneic recipients by 40-50%. These results suggest that at least one mechanism responsible for antigen-specific protection in EAE by MBP-liposomes operates through active suppression transferable by spleen cells.

Animals↗
PubMed1984

Suppression of chronic-relapsing experimental allergic encephalomyelitis in strain-13 guinea pigs by administration of liposome-associated myelin basic protein.

Juvenile strain-13 guinea pigs were challenged with isologous spinal cord in CFA. After recovery from the first EAE episode the animals were treated with guinea pig MBP inserted into liposomes, with cytochrome-c-liposomes, with MBP in saline or with MBP in IFA. Guinea pigs treated with MBP-liposomes showed a striking reduction in clinical signs and in the number and intensity of relapses. They displayed virtually no demyelinating lesions, and had comparatively little parenchymal inflammation in the spinal cord. Early T rosette levels showed an inverse correlation with the severity of histological lesions in the spinal cord but correlation with the clinical status at the time of rosette assay was less well defined.

Animals↗
PubMed1984

The role of myelin lipids in experimental allergic encephalomyelitis. Part 1. Influence on disease production by non-encephalitogenic doses of myelin basic protein.

Hartley guinea pig central nervous system (CNS) myelin has been purified and fractionated into its protein and lipid components. Experimental allergic encephalomyelitis (EAE) was induced in juvenile strain 13 guinea pigs with both lyophilized and fresh 'wet' myelin. However, a larger dose of lyophilized myelin was required to induce chronic EAE. Total myelin lipids, galactocerebrosides, gangliosides, phospholipids or proteolipids were combined with a non-encephalitogenic dose of myelin basic protein (MBP) and injected in juvenile Hartley guinea pigs. No clinical or histological manifestations of disease were observed. Parameters of immune functions indicated that the total myelin lipids augmented cell-mediated immune responses as measured by in vitro lymphocyte transformation and by a significant decrease in the percentage of peripheral early T cells. Only the proteolipids elicited delayed hypersensitivity reactions. Animals that received the phospholipid-MBP combination showed no changes when compared to animals injected with MBP alone. The results suggest that although the myelin lipids did not act synergistically with a non-encephalitogenic dose of MBP to induce EAE, they induced immunological changes and potentiated the immune response to MBP.

Animals↗
PubMed1984

Suppression of the IgE antibody response by glutaraldehyde-modified ovalbumin: dissociation between loss of antigenic reactivity and ability to induce suppression.

Ovalbumin (OA) was substituted with glutaraldehyde (GA) at various GA:OA ratios and several preparations were isolated by gel filtration according to molecular weight. Two GA-substituted but unpolymerized preparations (OA1-L and OA1-H) and 3 polymerized preparations of increasing molecular weight (OA4, OA175 and OA-POL) were obtained and were assessed for their ability to react with IgG and IgE antibodies directed against the native OA molecule, as well as for their ability to suppress the IgE antibody response. The results show that while both polymerized and unpolymerized GA-modified preparations lost their reactivity towards antinative OA antibodies, to a considerable extent, their ability to suppress the OA/IgE antibody response was directly dependent on polymerization. Pretreatment of CBA mice with unpolymerized OA preparations was ineffective while the effect of pretreatment with three polymers (OA4, OA175 and OA-POL) was directly dependent on the size of the polymer. The ability to induce IgG antibodies or delayed hypersensitivity to OA was not suppressed.

Aldehydes↗
PubMed1984

Demonstration of long-lived memory T suppressor cells in the IgE response.

Administration to mice of repeated small doses of glutaraldehyde-polymerized ovalbumin (OA-POL) results in drastic suppression of the IgE antibody response. The high anamnestic IgE antibody responses usually obtained after 2 injections of native OA in alum were completely abrogated when OA-POL was administered between the 2 immunizations. Treatment with OA-POL prior to a primary immunization with 2 micrograms DNP-OA in alum induced a profound suppression of both anti-DNP and anticarrier IgE responses. The suppression, which was detectable for at least 7 months, was antigen-specific, selective for the IgE class and was sensitive to treatment of spleen cells with anti-Thy-1.2 antibody and complement. Adoptive transfer of spleen cells from donors treated with OA-POL 200 days, 16 days or 200 and 16 days prior to transfer, resulted in different kinetics of suppression in the recipient. The results are consistent with the presence of long-lived IgE-selective T suppressor cell memory. The possibility that separate Ts and Ts memory cell populations are generated is discussed.

Animals↗
PubMed1983

Antigen- and IgE class-specific suppression mediated by T suppressor cells of mice treated with glutaraldehyde-polymerized ovalbumin.

Various size polymers are obtained following glutaraldehyde treatment of native ovalbumin (OA). OA-POL, approximately 35 X 10(6) daltons, was prepared at the isoelectric point of OA. Treatment of CBA mice with microgram amounts of OA-POL led to efficient antigen-specific suppression of IgE responses. IgG anti-OA antibodies were not suppressed. Transfer of cells from OA-POL-treated donors into normal, unprimed recipients interfered with the ability of these animals to mount a primary or secondary IgE response. In addition, cotransfer of spleen cells from OA-POL-treated mice along with OA (in alum)-primed cells, into irradiated syngeneic recipients resulted in IgE class-specific suppression that was abrogated by treatment of OA-POL donor cells with monoclonal anti-Thy 1.2 + complement. The presence or absence of T cells in the OA-POL population had no effect on IgG levels in the recipients. Analysis of the antigenic properties of OA-POL revealed 5-15% cross-reactivity with native OA as perceived by IgG or IgE antibodies. In contrast, OA-POL was highly cross-reactive at the T cell level as shown functionally by its potent induction of OA-specific, IgE-selective suppressor T cells. The results suggest that the beneficial effects of glutaraldehyde-modified allergens, recently introduced in the immunotherapy of atopic individuals may be due to the preferential exposure on the polymerized protein, of antigenic determinants generating T suppressor cells and to the selective loss of B cell-reactive determinants.

Animals↗
PubMed1981

Suppression of experimental allergic encephalomyelitis in guinea/pigs by liposome-associated human myelin basic protein.

Human myelin basic protein (MBP) was inserted into phosphatidyl-serine liposomes and Hartley guinea pigs were treated with 1 or 2 injections of MBP-liposomes mixture by the intracardial route before an encephalitogenic challenge with MBP in CFA. Other groups of guinea pigs were pretreated with equivalent amounts of MBP in saline or of MBP in IFA. Of 24 untreated animals, 22 developed EAE and died or had to be sacrificed within 15 days after challenge. Only 4 of 29 guinea pigs treated with either 75 microgram or 112 microgram MBP-liposomes developed clinical signs of the disease. In the group pretreated with MBP in saline, 11 of 15 animals died, whereas in the MBP-IFA group, only 4 out of 10 died. Histologic modifications were also decreased in the MBP-liposomes and MBP-IFA groups, but in many instances, clinical normal guinea pigs showed disseminated perivascular infiltrates in the brain and spinal cord. Delayed hypersensitivity reactions to MBP were positive in all but 1 animal tested. Early T-rosette levels followed essentially the clinical course of the disease: they were drastically decreased 7 days after challenge in the untreated and MBP-saline-treated groups, but remained essentially normal in the MBP-liposomes group throughout the experiment. Lymphocyte transformation tests carried out in parallel with soluble MBP and with MBP-liposomes indicated that animals in certain groups responded preferentially to 1 form or the other of the antigen. Compared with prevailing procedures, the single i.v. injection of a relatively small amount of liposome-associated MBP appears to represent a promising approach for the antigen-specific suppression of EAE.

Animals↗
PubMed1981

Naturally occurring antibodies to liposomes. II. Specificity and electrophoretic pattern of rabbit antibodies reacting with sphingomyelin-containing liposomes.

Sera obtained from rabbits after immunization with a variety of unrelated antigens contain antibodies that induce complement- (C) mediated lysis of sphingomyelin-containing liposomes in the absence of the relevant antigen from the membrane. Absorption or inhibition with dimyristoyl-phosphatidyl choline-containing liposomes were less effective than with sphingomyelin-containing liposomes in decreasing or abolishing C-dependent lysis of target-liposomes. Phosphoryl choline chloride inhibited the C-dependent lysis mediated by these antibodies, but only when used in high molar excess and in the presence of low antibody concentrations. Purified anti-liposome antibodies displayed an isoelectric focusing pattern consistent with a polyclonal response. The findings confirm the antibody nature of the anti-liposome activity of rabbit sera and indicate that their predominant specificity is directed against conformations of the phospholipid molecule in which the polar (phosphoryl choline) group does not have a major contribution.

Absorption↗
PubMed1980

Immunological tolerance of the mouse IgE system: dissociation between T cell tolerance and suppressor cell activity.

Immunological tolerance was induced in CBA mice with respect to both anti-hapten and anti-carrier IgE antibody production, following pretreatment of the animals with deaggregated ovalbumin. IgG antibody production was also affected. The tolerance was antigen-specific, was stable upon adoptive transfer to irradiated syngeneic recipients, but was reversed following booster. The extent and duration of the tolerant state depended on the dosage and number of tolerogen injections. Tolerogen administered after the initiation of the primary response was without effect. The pattern and duration of this tolerance suggested that T suppressor cells were not involved. The adoptive transfer of spleen cells from tolerogen-treated donors while being themselves unresponsive, failed to interfere with the induction of an immune response in the recipient. Evidence of T suppressor cell function was found in adoptive transfers, only after prolonged pretreatment of donors with a combination of tolerogenic and immunogenic forms of the carrier. These results suggested that T cell-dependent tolerance of the IgE antibody response operates via two distinct mechanisms, of which only one is provided by suppressor cell function.

Animals↗
PubMed1979

Naturally occurring antibodies to liposomes. I. Rabbit antibodies to sphingomyelin-containing liposomes before and after immunization with unrelated antigens.

Liposomes were prepared from a mixture of sphingomyelin, cholesterol, and dicetylphosphate or L-alpha-dimyristoyl phosphatidylcholine, cholesterol, and dicetylphosphate, in the presence of glucose. The amount of trapped glucose released from these liposomes was monitored after incubation with a variety of normal and immune sera in the presence of guinea pig complement. All normal rabbit sera tested were found to release, in the presence of complement, detectable amounts of trapped glucose from sphingomyelin-containing liposomes. After immunization with a variety of unrelated antigens, the anti-sphingomyelin liposome activity increased signficantly and in direct proportion to the number of injections, despite the fact that the liposomes used in the assay did not contain the relevant antigen used for immunization. Liposomes prepared from dimyristoyl phosphatidylcholine showed only marginal release of their trapped marker when assayed with the same rabbit sera and complement. These liposomes, however, were fully reactive when the appropriate antigen was inserted in their bilayer structure. The antiliposome activity was associated mainly with the IgM antibody class. These results raise the interesting possibility that antigenic stimulation may trigger the activation of lymphocyte clones directed against autologous cell-membrane components that cross-react with artificial model membranes containing sphingomyelin.

Animals↗