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M Kopf

Publications and source records attributed to M Kopf.

70 records · Page 4Linked to original sources
PubMed1995

Infection of IL-4-deficient mice with the parasitic nematode Brugia malayi demonstrates that host resistance is not dependent on a T helper 2-dominated immune response.

Resistance of intact mice to infection with the filarial nematode, Brugia malayi is dependent on the presence of T cells. To investigate the role of Th2 cells in this protection, mice with a targeted disruption of the IL-4 gene were infected with different developmental stages of B. malayi. We examined the phenotypic changes in the immune response and the survival of each stage in these mice. In wild-type mice, adult female worms induce Th2 responses, characterized by antigen-specific IgG1 production, elevated IgE, and marked IL-4 secretion by splenocytes stimulated in vitro with Brugia extract. However, first stage larvae (microfilariae), induce Th1 responses with the appearance of antigen-specific IgG2a, IgG2b, and IgG3 and IFN-gamma secretion by splenocytes. Infection of IL-4-deficient mice revealed a dramatic change in the response to adult worms, with a severe reduction in IgG1 production and a corresponding increase in the production of IgG2a, IgG2b, IgG3, and IFN-gamma release. The switch to Th1-type responses was particularly marked in IL-4-deficient recipients of female worms, which continually release live microfilariae. In the absence of IL-4, down-regulation of the microfilarial-induced Th1 response does not occur. Despite these profound alterations to the immune response in IL-4-deficient mice, survival of infective larvae, adult worms, or microfilariae in the peritoneal cavity was unaffected. In mice, therefore, the prominent Th2-type response elicited by filarial parasites may not be an essential component of the host protective immune response.

Animals↗
PubMed1995

Impaired mucosal immune responses in interleukin 4-targeted mice.

Interleukin 4-targeted (IL-4-/-) mice are defective in T helper (Th)2 cytokine production as determined after nematode infection. As Th2 cells appear to be selectively induced by oral immunization we investigated the ability of IL-4-/- mice to respond to perorally administered antigen. We found that IL-4-/- mice failed to respond to soluble protein antigens given perorally together with cholera toxin (CT) as a mucosal adjuvant. In contrast to wild-type mice no or poor anti-keyhole limpet hemocyanin (KLH) or anti-ovalbumin (OVA) B cell responses were observed in gut lamina propria, spleen, or serum of IL-4-/- mice after oral immunization. In addition, mucosal immunization failed to stimulate antigen-specific T cell responses in these mice. The lack of responsiveness was specific for mucosal administration of antigen and was not seen after intravenous injections with antigen and CT-adjuvant. The systemic adjuvant effect of CT was not impaired in IL-4-/- mice as evidenced by the strong enhancement of anti-KLH responses after intravenous immunization with KLH plus CT as opposed to KLH alone. However, CT as an immunogen, in contrast to KLH or OVA, stimulated significant mucosal and systemic immune responses in IL-4-/- mice after oral immunization. Both serum and intestinal IgA anti-CT antibodies were demonstrable in IL-4-/- mice as well as in wild-type mice. Total IgA levels in gut lavage and in serum of immunized IL-4-/- mice were of similar magnitude as in wild-type mice, suggesting that the ability of naive B cells to undergo isotype switch-differentiation from IgM to IgA in IL-4-/- mice did not appear to be impaired. Immunohistochemical analysis of Peyer's patches demonstrated a complete inability to form germinal centers in IL-4-/- mice in contrast to wild-type mice. Our data suggest that IL-4-/- mice are unable to respond to oral/mucosal immunization due to a failure to stimulate antigen-specific cells required to induce germinal center reactions in the Peyer's patches. Our findings demonstrate that IL-4 and probably functional Th2 cells are required for induction of gut mucosal antibody responses.

Adjuvants, Immunologic↗
PubMed1995

B-cell maturation in chimaeric mice deficient for the heat stable antigen (HSA/mouse CD24).

The murine differentiation marker heat stable antigen (HSA) is a GPI-anchored surface glycoprotein showing strong expression on immature B- and T-lymphocytes and gradually reduced expression during maturation. Although HSA has been suggested to be involved in adhesion and/or signalling, its function has not been clearly demonstrated so far. In order to elucidate the function of HSA, we analysed chimaeric mice that were generated by targeted disruption of both HSA alleles in ES cells. These mice contain normal numbers of peripheral B-cells and normal serum IgM and IgG titres of ES cell-derived allotype, demonstrating that HSA expression on B-cells is not an absolute requirement for their maturation. However, a reduction in immature B-cells in the bone marrow and an altered degree of bone marrow and blood chimaerism suggest that HSA expression influences the maturation of B-cells.

Alleles↗
PubMed1995

Interleukin-4 is required for the induction of lung Th2 mucosal immunity.

Aerosol antigen challenge of ovalbumin-sensitized mice induced an eosinophilic airway inflammation that was dependent on interleukin (IL)-5 and CD4+, but not CD8+, T lymphocytes. The involvement of the Th2 phenotype of CD4+ T cells was supported by demonstrating that FACS-sorted purified lung T cells from sensitized, but not control, mice produced IL-4, IL-5, and IL-10 after activation of the CD3/TCR complex. To determine the role of IL-4 in this process, we used mice in which the gene for IL-4 was deleted by homologous recombination. Antigen challenge of IL-4 gene-targeted mice resulted in a marked attenuation of eosinophilic inflammation and IL-5 secretion. To more fully understand the time when IL-4 was involved, we administered a neutralizing anti-IL-4 antibody (11B11) either immediately before antigen challenge or during immunization. Inhibition of IL-4 before antigen challenge had little effect on antigen-induced eosinophil infiltration. However, when 11B11 was administered during immunization, there was a marked reduction in eosinophil infiltration. Cross-linking of the CD3/TCR complex of FACS-sorted lung T cells revealed that only when anti-IL-4 was administered during immunization was there an inhibition of T cell-derived IL-5 and IgE production. These results suggest that IL-4 is central both to the induction of a local Th2 response and to the development of eosinophilic inflammation of the lung. Moreover, we suggest a sequential involvement of IL-4 and IL-5, with IL-4 committing naive T cells to a Th2 phenotype which upon activation by aerosol provocation secrete IL-5, resulting in eosinophil accumulation.

Animals↗
PubMed1994

The role of interleukin-6 in mucosal IgA antibody responses in vivo.

In mice with targeted disruption of the gene that encodes interleukin-6 (IL-6), greatly reduced numbers of immunoglobulin A (IgA)-producing cells were observed at mucosae and grossly deficient local antibody responses were recorded after mucosal challenge with either ovalbumin or vaccinia virus. The IgA response in the lungs was completely restored after intranasal infection with recombinant vaccinia viruses engineered to express IL-6. These findings demonstrate a critical role for IL-6 in vivo in the development of local IgA antibody responses and illustrate the effectiveness of vector-directed cytokine gene therapy.

Animals↗
PubMed1994

Impaired immune and acute-phase responses in interleukin-6-deficient mice.

Interleukin-6 (IL-6) is a multifunctional cytokine that regulates various aspects of the immune response, acute-phase reaction and haematopoiesis (for reviews see refs 1, 2). In vitro, leukaemia inhibitory factor, oncostatin M, ciliary neurotrophic factor and interleukin-11 display overlapping activities with IL-6. This functional redundancy may be explained by the interactions of specific binding receptors with a common signal-transducing receptor (gp130) (for reviews see refs 3, 4). To elucidate the unique function of IL-6 in vivo, we have disrupted the IL-6 gene by homologous recombination. IL-6-deficient mice develop normally. They fail to control efficiently vaccinia virus and infection with Listeria monocytogenes, a facultative intracellular bacterium. The T-cell-dependent antibody response against vesicular stomatitis virus is impaired. Further, the inflammatory acute-phase response after tissue damage or infection is severely compromised, whereas it is only moderately affected after challenge with lipopolysaccharide. We conclude that IL-6 production induced by injury or infection is an important in vivo SOS signal which coordinates activities of liver cells, macrophages and lymphocytes.

Acute-Phase Reaction↗
PubMed1994

The immune response to Plasmodium chabaudi malaria in interleukin-4-deficient mice.

Interleukin(IL)-4 promotes the development of T helper (TH)2 cells, induces immunoglobulin class switching to IgG1 and is thought to be essential for switching to IgE. During a primary infection with the erythrocytic stages of Plasmodium chabaudi chabaudi, TH1 and TH2 cells specific for the parasite appear sequentially as infection progresses. To dissect the possible role of TH2 responses at the later stages of infection, mice with a targetted disruption of the IL-4 gene were infected with P. chabaudi. IL-4-deficient mice were able to control and clear a primary infection, although recrudescent parasitemias were significantly higher in these mice compared with wild-type littermates; demonstrating that IL-4 per se is not required for parasite elimination. To evaluate the actual impairment of TH2 functions in the absence of IL-4 in vivo during an infection with P. chabaudi; the cellular and humoral responses to the parasite generated in vitro and in vivo were compared in the two types of mice. Our data indicate that in vitro TH1 responses and ex vivo IL-12 mRNA levels were sustained in the IL-4-deficient mice compared with wild-type littermates. Correspondingly, TH2-associated cytokine mRNA such as IL-5 and IL-6, but not IL-10, were reduced early in infection in the deficient animals. However, these cytokines were expressed at comparable levels at the later stages of infection in both types of mice. Reflecting these differences in TH function, IgG1 responses were decreased in vitro and delayed in vivo, whereas IgG2a and IgG2b responses appeared earlier in vivo in the deficient mice. Strikingly, IgE secretion was not blocked in vivo in the deficient mice; the onset of the synthesis of IgE mRNA was delayed during infection and the amount of circulating IgE was five times lower than in the wild-type littermates after 5 weeks of infection. All these impairments of TH2-related activities were insufficient to affect parasite clearance in the deficient mice, probably due to the fact that such activities were only delayed and could take place normally at the later stages of infection.

Animals↗
PubMed1994

Interleukin-6 is required in vivo for the regulation of stem cells and committed progenitors of the hematopoietic system.

The development of blood cells from hematopoietic stem cells is controlled by multiple cytokines. These growth factors influence survival, cell cycle status, differentiation into lineage-committed progenitors, final maturation into blood cells, and perhaps self-renewal of stem cells. The specific contribution of IL-6 to these processes in vivo was evaluated in mice with a targeted disruption of the IL-6 gene. Decreases in the absolute numbers of CFU-Sd12 and preCFU-S, as well as in the functionality of LTRSC in these mutant mice, suggests a role for IL-6 in the survival, self-renewal, or both of hematopoietic stem cells and early progenitors. In addition, as a result of the IL-6 deficiency, the control between proliferation and differentiation of the progenitor cells of the granulocytic-monocytic, megakaryocytic, and erythroid lineages into mature blood cells is altered, leading to abnormal levels of committed progenitors of these lineages and to a slow recovery from hematopoietic ablation.

Animals↗
PubMed1993

Resistance of mice deficient in IL-4 to retrovirus-induced immunodeficiency syndrome (MAIDS)

The murine acquired immunodeficiency syndrome (MAIDS) is induced by a defective murine leukemia virus and has many symptoms similar to those found in patients infected with the human immunodeficiency virus. The presence of both B cells and CD4+ T cells is critical for the development of the disease. Furthermore, a Th2 cytokine response dominates during the progression of the disease. When interleukin-4 (IL-4)-deficient mice that are defective in Th2 cytokine responses were infected, there was no lethality, and the development of the T cell abnormalities associated with MAIDS was delayed. These data suggest that IL-4 or a Th2 response is involved in the development of retrovirus-induced immunodeficiency in mice.

Animals↗
PubMed1993

Disruption of the murine IL-4 gene blocks Th2 cytokine responses.

Murine T-helper clones are classified into two distinct subsets (Th1 and Th2) on the basis of their patterns of lymphokine secretion. Th1 clones secrete interleukin-2 (IL-2), tumour necrosis factor-beta (TNF-beta) and interferon-gamma (IFN-gamma), whereas Th2 clones secrete IL-4, IL-5 and IL-10 (ref. 1). These subsets are reciprocally regulated by IL-4, IL-10 and IFN-gamma and differentially promote antibody or delayed-type hypersensitivity responses. To evaluate whether IL-4 is required for mounting Th2 responses, we generated IL-4-mutant mice (IL-4-/-) and assessed the cytokine secretion pattern of T cells both from naive and Nippostrongylus brasiliensis infected mice. CD4+ T cells from naive IL-4-/- mice failed to produce Th2-derived cytokines after in vitro stimulation. The levels of Th2 cytokines IL-5, IL-9 and IL-10 from CD4+ T cells obtained after nematode infection were significantly reduced. The reduced IL-5 production in IL-4-/- mice correlated with reduced helminth-induced eosinophilia, which has been shown to be dependent on IL-5 in vivo. We conclude that IL-4 is required for the generation of the Th2-derived cytokines and that immune responses dependent on these cytokines are impaired.

Alleles↗
PubMed1991

Molecular requirements for the mu-induced light chain gene rearrangement in pre-B cells.

During B cell differentiation rearrangement of immunoglobulin (Ig) genes is partially regulated by the Ig proteins. Rearrangement of heavy (H) chain genes is inhibited, whilst that of light (L) chain genes is induced by the membrane form of the mu H chain. In order to analyse additional structural requirements of mu induced L chain gene rearrangement we transfected wild-type mu and mutant mu constructs lacking functional exons encoding the first or second constant domains into Abelson murine leukemia virus (AMuLV) transformed pre-B cells. All mu chains are expressed on the surface of the pre-B cell and all associate with omega and iota, two proteins forming a surrogate light chain, necessary for mu membrane expression. Nevertheless, only wild-type mu and not the mutant mu proteins promote L gene rearrangement. A heterodimer of proteins with Mr of 33 kd and 36 kd was found associated with wild-type but not with the mutant mu proteins. Continuous presence of mu is required for L chain gene recombination since loss of mu stopped and readdition of mu started L gene rearrangement. We propose that the protein complex composed of mu and the 33 kd/36 kd protein heterodimer is responsible for the activation of the L chain gene locus and its rearrangement.

Animals↗
PubMed1988

Electrophysiological and ultrastructural studies on reversible neural conduction disturbance after high voltage discharge.

High-voltage condenser discharges exerting a field strength of up to 1000 V/cm (discharge time constant 0.24-8 msec) applied to isolated sciatic frog nerve lead to disturbances of the propagation of action potentials including transient complete block of conduction. Such conduction disturbances are normally reversible within minutes. Inhibition of the activity of the membrane-bound Na+-K+ATPase prevents the recovery from conduction block. Withdrawal of external Ca2+ also prevents recovery, whereas blockade of protein synthesis by cycloheximide has no influence. The velocity of recovery depends on the temperature, with temperature coefficients (Q10) from 1.31 to 1.84 between 2 degrees and 30 degrees C. Transmission electron microscopy of nerves subjected to strong discharges shows alterations of the myelin sheath (splitting and cleft formation) which are, however, not specific for this mechanism of injury. No alterations are seen in the region of the free axoplasmic membrane of the node of Ranvier or in organelles. The results suggest a breakdown of the transmembrane ionic gradient causing the conduction disturbance.

Action Potentials↗
PubMed1983

Lung strips from guinea pigs as test system for lipoxygenase inhibitors. Inhibition of arachidonic acid-induced contractions by 3-t-butyl-4-hydroxyanisole and nordihydroguaiaretic acid.

Lung strips and tracheal spirals from guinea pigs and rats were compared as test systems for lipoxygenase inhibitors. The contraction of the smooth muscle was induced by addition of arachidonic acid. Lung strips of guinea pigs proved to be the most suitable in vitro model. Under basal conditions half-maximal contraction was produced by 13 microM arachidonic acid (AA) which was strongly inhibited by 50 microM nordihydroguaiaretic acid (NDGA) or 100 microM 3-t-butyl-4-hydroxyanisole (BHA). NDGA and BHA caused a shift of response towards higher concentrations of AA. BHA also produced pronounced dilatations of both basal tonus and carbachol-induced contractions of the preparations from the respiratory tract. It is concluded that the actions of NDGA and BHA on the airway preparations are due to inhibition of the lipoxygenase reaction and, therefore, of leukotriene synthesis. The assumption of the lipoxygenase inhibition is supported by their action on purified lipoxygenase from rabbit reticulocytes which was inhibited by 50% by 0.5 microM NDGA and 160 microM BHA. In contrast, the antioxidant 2,6-di-t-butyl-4-hydroxytoluene (BHT) did not inhibit at all at 1 mM. To the knowledge of the authors this is the first evidence so far reported for the bronchodilating action of BHA.

Animals↗