[The new research frontier on prion disease].
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
M B Fischer
Publications and source records attributed to M B Fischer.
Inhibition of IL-10 protein synthesis induces major histocompatibility complex class II gene expression in class II-deficient patients.
Major histocompatibility complex (MHC) class II deficiency is an inherited autosomal recessive combined immunodeficiency, characterized by a lack of constitutive expression of the human leukocyte antigen (HLA) class II genes. The patients investigated in this study are histoidentical twin brothers with a new phenotype in MHC class II deficiency. Examination of HLA-D locus genes in their fractionated peripheral mononuclear cells (MNCs) revealed an unusual and uncoordinated mRNA pattern. Here we analyzed the distribution of pro- and anti-inflammatory cytokines expressed in these patients' adherent and nonadherent MNCs. We show that gene expression of IL-1 alpha, IL-1 beta, IL-6, granulocyte-colony-stimulating factor, and IL-10 was induced in both cell fractions, whereas increased mRNA levels of interferon-gamma and the inducible nitric oxide synthase were exclusively detected in the patients' nonadherent MNCs. As IL-10 is known to be able to downregulate transcription of MHC class II and expression of IL-10 in the patients' MNCs was increased, we investigated the regulatory function of this cytokine. Interestingly, inhibition of IL-10 protein synthesis with IL-10-specific antisense oligonucleotide DNA (IL-10-AS-ODN) induced HLA-D locus genes in these MHC class II-deficient patients. Exposure of the nonadherent cell fraction to IL-10-AS-ODN resulted in a profound induction of a previously absent DR beta 1 and DP alpha gene expression. HLA-DQ beta mRNA levels, however, were increased in both the adherent and the nonadherent MNC population. Albeit expression of HLA-D locus genes was inducible via inhibition of IL-10 translation, surface expression of HLA class II antigens on the patients' MNCs was essentially negative. The data presented support the concept of a coordinated network of pro- and anti-inflammatory cytokine regulation and this network obviously has a significant role in the cell-type-specific regulation of MHC class II expression.
Cells, Cultured↗
Murine astrocytes express a functional chemokine receptor.
Elevated levels of chemokines have been observed in various diseases of the CNS. Little is known, however, about how these chemokines affect parenchymal cells of the CNS. The current studies examine astrocyte chemotaxis to the mouse chemokine macrophage inflammatory protein-1alpha (MIP-1alpha). Murine astrocytes demonstrate directed migration along a chemical gradient in response to 10(-10)-10(-8) M MIP-1alpha. Peak chemotactic responses are noted at 10(-9) M. MIP-1alpha-induced astrocyte migration is specifically inhibitable with pertussis toxin, suggesting a role for Galphai proteins in the signaling process. RT-PCR and in situ hybridization were used to identify expression of the murine CCR1 MIP-1alpha receptor on astrocytes. Astrocytes contain mRNA for CCR1, but messages for CCR4 and the orphan chemokine receptor MIP-1alphaR-like#1 were not detected. The combined results suggest that a functional chemokine receptor is expressed on resident cells of the CNS. We speculate that the interactions of chemokines with astrocytes are involved in inflammatory reactions of the CNS.
Animals↗
Increased susceptibility to endotoxin shock in complement C3- and C4-deficient mice is corrected by C1 inhibitor replacement.
Endotoxin shock is a life-threatening syndrome associated with a Gram-negative infection and mediated by a systemic inflammatory response. As a major effector of inflammation, the complement system has been implicated in both the pathogenesis and the protection from endotoxin shock. To clarify the role of complement in endotoxin shock, we have used mice totally deficient in either complement component C3 or C4. We found that both the C3- and C4-deficient mice were significantly more sensitive to endotoxin than wild-type controls. The endotoxin-challenged complement-deficient mice failed to clear endotoxin efficiently from the circulation and this led to excess consumption of C1 inhibitor protein (C1 INH), a major regulator of both complement and the contact system of blood coagulation. Replacement of C1 INH rescued the endotoxin-challenged complement-deficient mice from shock and death. These findings suggest a novel therapy for treatment of endotoxemia with C1 INH protein.
Animals↗
Complement and the immune response.
This past year has seen a major advance in our understanding of how the complement system enhances the adaptive immune response. The use of in vivo models has revealed that direct coupling of C3d to antigen is sufficient to dramatically reduce the amount of antigen required for a secondary response. At least one important requirement for the enhancing effect was determined to be expression of the CD21 (C3d receptor) on B cells.
Animals↗
Antigen presentation by common variable immunodeficiency (CVID) B cells and monocytes is unimpaired.
CVID is a primary immunodeficiency syndrome comprising a heterogeneous group of patients with hypogammaglobulinaemia and defective formation of specific antibodies. Previous studies demonstrated defective T cell responsiveness to antigen in a major subgroup of patients. In the present study we investigated the capacity of peripheral blood monocytes and Epstein-Barr virus (EBV)-transformed B cell lines from seven patients with CVID, including two patients expressing an extended MHC haplotype described to be associated with CVID, to present antigen (Tet. Tox.) to CD4+ antigen-specific T cell lines from healthy controls. The results presented show an unimpaired capacity of peripheral blood monocytes to present antigen in all patients studied. In addition, the present study demonstrates for the first time that CVID B cells function normally as antigen-presenting cells (APC). These findings indicate that expression of a certain MHC phenotype in CVID is not associated with a defect in the presentation of recall antigen by monocytes and B cells. Based on these studies, uptake, processing and re-expression of recall antigen in association with MHC class II molecules on the APC surface are functional and there is no indication for structural abnormalities of the MHC class II molecules expressed by the patients studied that could be essential for their function in antigen binding and presentation.
Antigen Presentation↗
T cell activity and cytokine production in X-linked agammaglobulinemia: implications for vaccination strategies.
In the 5 X-linked agammaglobulinemia (XLA) patients studied we show that memory T cells are present and that T lymphocytes proliferate normally to mitogens, monoclonal antibodies and, in particular, to recall antigens demonstrating normal in vivo T cell priming despite the absence of B cells. Furthermore, in vitro T cell activation in response to both T cell receptor-independent and T-cell receptor-dependent signals leads to a pattern of cytokine production characteristic of primed T cells and necessary for normal T cell function. These data are in good agreement with results obtained in gene-targeted mice and further support the concept that the absence of B cells does not impair induction of in vivo T cell memory and effector function which is generally considered to be of great importance in conferring protection against viral infections. Thus, while there is no risk of inducing infections in XLA patients by administering vaccines containing killed viruses or recombinant viral proteins, stimulation of T cell immunity by such vaccines may be of potential benefit particularly in the defense against infections with viruses such as the hepatitis B virus to which hypogammaglobulinemic patients are particularly exposed.
Adolescent↗
Regulation of the B cell response to T-dependent antigens by classical pathway complement.
Mice deficient in complement components C3 (C3 -/-) and C4 (C4 -/-) were found to have a profound defect in their Ab response to a T-dependent Ag (bacteriophage (phi X174). Characterization of the deficient mice demonstrated a diminished level of peanut agglutinin+ germinal centers and a failure in isotype switching despite normal B cell signaling in vitro. The nature of the defect was found to lie at the B cell level, as the T cells were primed in C3- and C4-deficient mice as well as those in wild-type mice. These results, and the finding that the defect could be partly reversed by a 10-fold increase in Ag dose, support the hypothesis that covalent attachment of complement ligands, i.e., C3b and C3d to the Ag-Ab complex, increases its immunogenicity.
Animals↗
Activation via the antigen receptor is impaired in T cells, but not in B cells from patients with common variable immunodeficiency.
The patients included in this study belong to a subset of common variable immunodeficiency (CVID) patients whose peripheral blood T cells have a T cell receptor (TCR)-mediated activation defect leading to impaired expression of the interleukin (IL)-2 gene upon stimulation with recall antigens (tetanus toxoid, Escherichia coli) or superantigens (staphylococcal enterotoxins). In the present report we demonstrate that the patients' peripheral blood T cells failed to generate the second messenger inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) following stimulation with superantigen or mAb specific for the monomorphic region of the TCR beta-chain. Patients' T cell lines were also impaired in generating Ins(1,4,5)P3 when stimulated with tetanus toxoid-pulsed autologous monocytes. Addition of a second or third co-stimulatory signal provided by recombinant IL-2, CD28 or both had no effect on the Ins(1,4,5)P3 formation of the patients' antigen-driven T cell lines. The T cell activation defect, however, was not absolute, as Ins(1,4,5)P3 formation in the patients' T cells after phytohemagglutinin or aluminium fluoride stimulation was normal. The impairment in signal transduction via the T cell antigen receptor was limited to the patients' T cells, as no activation defect after ligation of surface immunoglobulin, the antigen receptor on B cells, could be detected.
Antibodies, Monoclonal↗
Disruption of the Cr2 locus results in a reduction in B-1a cells and in an impaired B cell response to T-dependent antigen.
Covalent attachment of activated products of the third component of complement to antigen enhances its immunogenicity, but the mechanism is not clear. This effect is mediated by specific receptors, mCR1 (CD35) and mCR2 (CD21), expressed primarily on B cells and follicular dendritic cells in mice. To dissect the role of mCR1 and mCR2 in the humoral response, we have disrupted the Cr2 locus to generate mice deficient in both receptors. The deficient mice (Cr2-/-) were found to have a reduction in the CD5+ population of peritoneal B-1 cells, although their serum IgM levels were within the range of normal mice. Moreover, Cr2-/- mice had a severe defect in their humoral response to T-dependent antigens that was characterized by a reduction in serum antibody titers and in the number and size of germinal centers within splenic follicles. Reconstitution of the deficient mice with bone marrow from MHC-matched Cr2+/+ donors corrected the defect, demonstrating that the defect was due to B cells themselves. These results indicate an obligatory role of B cell complement receptors in responses of the B cells to protein antigens.
Animals↗
Anti-inflammatory properties of human serum IgA: induction of IL-1 receptor antagonist and Fc alpha R (CD89)-mediated down-regulation of tumour necrosis factor-alpha (TNF-alpha) and IL-6 in human monocytes.
A deregulated expression and/or release of large amounts of inflammatory cytokines such as IL-1 and TNF-alpha accounts for most pathophysiological events in a variety of systemic inflammatory diseases, the effect being mediated by the interaction of these cytokines with their respective receptors. IL-1 receptor antagonist (IL-1Ra), mainly produced by monocytes/macrophages, is an inhibitor of IL-1 activity. The present study shows that human serum IgA induces significant IL-1Ra release in human peripheral blood mononuclear cells and adherent monocytes. IgA induced higher levels of IL-1Ra than Haemophilus influenzae type b (Hib) expressing lipopolysaccharide (LPS), purified LPS or phorbol myristate acetate (PMA), without induction of IL-1 beta release, and even inhibited LPS-induced IL-1 beta release. Induction of IL-1Ra by IgA could be detected both at the mRNA and protein levels in resting and activated monocytes. Ligation of Fc alpha R with MoAb My-43 or treatment with human serum IgA induced protein tyrosine phosphorylation in human monocytes, and herbimycin A, a specific inhibitor of protein tyrosine kinase activity, inhibited IgA-induced IL-1Ra production, suggesting that Fc alpha R-mediated induction of tyrosine phosphorylation is required for the IgA-induced stimulation of IL-1Ra release. In addition, triggering of Fc alpha R with MoAb specifically down-regulated TNF-alpha and IL-6 release in human monocytes activated with Hib. By the induction of IL-1Ra and down-regulation of the release of inflammatory cytokines such as IL-1 beta, TNF-alpha and IL-6, interaction of IgA with human monocytes may actively contribute to the regulation of the inflammatory response.
Adult↗
The effects of N-methyl-D-aspartate agonists and antagonists on isolated bovine cerebral arteries.
This pharmacologic study examines the direct cerebrovascular effects of N-methyl-D-aspartate (NMDA) receptor agonists and antagonists to determine whether large cerebral arteries have NMDA receptors. Bovine middle cerebral arteries were cut into rings to measure isometric tension development in vitro. Two competitive agonists, L-glutamate and NMDA, each had negligible effects on ring tension in the absence of exogenous vasoconstrictors. L-glutamate (in high concentrations) produced direct relaxation of potassium (K+)-constricted arteries, but the relaxation was not selective for L-glutamate, D-glutamate, or mannitol. Relaxation with L-glutamate was abolished when it was isosmotically substituted in the K(+)-rich medium. NMDA (in the absence or presence of glycine) and two competitive antagonists, 2-amino-5-phosphopentanoic acid (AP5) and (+/-)-3-(s-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), each had little effect on the tone of arteries preconstricted with potassium or the stable thromboxane A2 analog U-46,619. Three noncompetitive antagonists (S(+)-ketamine, dizocilpine, and dextrorphan) and their steroeisomers (R(-)-ketamine, (-)MK-801, and levorphanol) each produced dose-dependent relaxation of K(+)- or U-46,619-constricted arteries; relaxation was not selective for the (+) or (-) stereoisomers. These results suggest that large cerebral arteries lack NMDA receptors mediating constriction or relaxation. All noncompetitive antagonists dilated cerebral arteries, but by mechanisms that were not stereospecific.
Animals↗
Brief report: twin boys with major histocompatibility complex class II deficiency but inducible immune responses.
Explore the source record for details and available documents.
Antibody Formation↗
Immunization of chimpanzees with recombinant gp160, but not infection with human immunodeficiency virus type 1, induces envelope-specific Th1 memory cells.
The human immunodeficiency virus (HIV) type 1 envelope protein (recombinant [r] gp160)-induced T cell lymphokine release pattern of chimpanzees immunized with HIVIIIB rpg160 tested and compared with rpg160-induced lymphokine releases of T cells from unimmunized, HIV-1-infected chimpanzees. The results showed that infection of chimpanzees with HIV-1 did not induce rgp160-specific memory T cells (as evidenced by the lack of Th1 and 2 type lymphokine releases after rgp160 stimulation). In contrast, T cells of rgp160-immunized chimpanzees released Th1 type lymphokines upon stimulation with rgp160 of HIVIIIB, HIVMN, and HIVRF. release was comparable whether chimpanzees were immunized with rgp160 only or also challenged with HIV-1 and protected or not protected. Thus, rgp160 immunization leads to generation of Th1 type memory cells. Whether Th1 type responses contribute to protection against HIV-1 infection has yet to be clarified.
Animals↗
Defective TCR surface expression associated with impaired TCR beta-chain assembly in a patient with cutaneous T-cell lymphoma.
We report on a patient with cutaneous T-cell lymphoma (CTCL) of long-standing duration. Phenotypic analysis of his peripheral blood mononuclear cells revealed an increased CD4+ T-helper subset and a decreased CD8+ cytotoxic T-cell population. Eighty-three to ninety-three percent of the patient's CD4+ T cells in the peripheral blood and 70% of the CD4+ T cells in the lesional skin lacked surface expression of the TCR/CD3 complex and showed a clonal rearrangement pattern of the TCR gamma-chain gene (V11-J1/J2). The lack in TCR surface expression correlated with defective assembly of the TCR beta-chain. Although mRNA for the TCR constant region beta 1 was found in the patient's purified CD4+ TCR-CD3- T cells, no intracytoplasmic TCR beta protein was detectable. In contrast, the patient's purified CD4+ TCR-CD3- T cells not only expressed mRNA specific for the TCR alpha-chain and for all CD3 chains, but intracytoplasmic TCR alpha and CD3 epsilon proteins could also be found. The lack of TCR beta protein clearly explains the defective surface expression of the TCR/CD3 complex in the patient's malignant T cells.
CD3 Complex↗
Reduced IL-2 expression upon antigen stimulation is accompanied by deficient IL-9 gene expression in T cells of patients with CVID.
Patients with common variable immunodeficiency (CVID) are heterogeneous in the clinical manifestation of the disease as well as in the underlying mechanisms leading to the immunodeficiency. In a previous study we identified a subgroup of patients with a primary immunodeficiency disease affecting IL-2 and IFN-gamma gene expression. The T cells of these patients revealed impaired proliferative response and reduced levels of IL-2 and IFN-gamma-specific mRNA after antigen stimulation in vitro, while cellular and molecular response to phorbol ester and the calcium ionophore ionomycin (PMA+IM) or anti-CD3 monoclonal antibodies (MoAbs) (OKT3) were comparable to those of healthy control individuals. Here we show that stimulation of these patients' T cells with tetanus toxoid (TT) resulted in dramatically reduced levels of IL-2, IL-9 and IFN-gamma mRNA, while IL-3 gene expression in three patients was comparable or even increased to the healthy controls. As expected, addition of exogenous IL-2 to tetanus toxoid pulsed cultures had virtually no effect on IL-2 transcription, but corrected the defect in IL-9 gene expression, while IFN-gamma mRNA levels were still reduced. In conclusion, these data suggest that recombinant IL-2 alone is not able to induce the IL-9 gene adequately in our patients, but clearly increases IL-9 mRNA levels in combination with tetanus toxoid.
Antigens↗
A defect in the early phase of T-cell receptor-mediated T-cell activation in patients with common variable immunodeficiency.
Common variable immunodeficiency (CVID) is characterized by an impairment of specific antibody production and a decrease in all or selected Ig isotypes. Abnormalities at the level of the B cells, T cells, and antigen-presenting cells have been described. In the present study, we have focused our attention on T-cell activation in CVID. T cells from 15 of 24 patients failed to respond to recall antigens (eg, tetanus toxoid, Escherichia coli). Of these 15 patients, 11 were studied in detail and showed significantly decreased T-cell proliferative responses and/or decreased interleukin-2 and interferon-gamma production on T-cell receptor-mediated stimulation with recall antigens and superantigens (staphylococcal enterotoxins [SE]); however, T-cell response to mitogens (anti-CD3 monoclonal antibody, phytohemagglutinin) was normal. The defect in interleukin-2 and interferon-gamma release on tetanus toxoid stimulation could also be documented in purified CD4 T cells of the patients and was present in patients with high and normal CD8 counts alike. Furthermore, patients' T cells failed to mount a significant elevation in free intracellular calcium (Ca++ flux) in response to superantigen, whereas the response to phorbol myristate acetate and ionomycin, bypassing receptor-mediated signaling, was unimpaired. These results indicate a defect in the early phase of T-cell activation after triggering of the T-cell receptor in a significant subgroup of CVID patients.
Adolescent↗
Human serum IgA downregulates the release of inflammatory cytokines (tumor necrosis factor-alpha, interleukin-6) in human monocytes.
While the protective effect of IgA antibodies against infection of the mucosal surfaces is well documented, the mechanisms involved are not entirely clear. The aim of the current study is to investigate the effect of human serum IgA on the release of inflammatory cytokines in human monocytes activated with a particulate stimulus, Haemophilus influenzae type b (Hib), or soluble lipopolysaccharide (LPS) purified from Escherichia coli. Our results show that IgA downregulates tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) production, whereas IgG examined in parallel had no effect. IgA had no inhibitory effect on Hib-induced granulocyte-macrophage colony-stimulating factor release. TNF-alpha and IL-6 release were downmodulated if IgA was present during cytokine induction, and IgA was also inhibitory if added to Hib-pretreated monocytes during the phase of cytokine release. These findings indicate that there are at least two mechanisms whereby IgA antibodies can downregulate TNF-alpha and IL-6 release in human monocytes: by a mechanism acting during the time of monocyte activation, and a mechanism that downregulates the production and/or the release of these cytokines in activated monocytes. Regulation of TNF-alpha and IL-6 release by IgA may be among the antiinflammatory mechanisms preventing an uncontrolled release of potentially noxious levels of inflammatory cytokines during acute and/or chronic inflammation.
Antigen-Presenting Cells↗