PubMed Health⌕ Search

Biomedical subjects

G Köhler

Publications and source records attributed to G Köhler.

At least 19 recordsLinked to original sources
PubMed1995

[Collagenous sprue].

HISTORY AND FINDINGS: A 45-year-old man with type I diabetes mellitus was admitted to hospital because of colicky abdominal pain and 5-6 watery stools daily. Upper gastrointestinal endoscopy showed nearly total atrophy of the villi in the duodenum and jejunum suggesting coeliac disease. However, gluten-free diet for 2 weeks brought no improvement. Another examination of the biopsy 6 weeks after the first endoscopy revealed extensive collagen deposition in the lamina propria of the small intestine, giving the diagnosis of collagenous sprue. TREATMENT AND COURSE: Parenteral nutrition, lactulose, cisapride, cholestyramine, doxycycline, paromomycin, vancomycin and octreotide failed to affect the loss of fluid from the gut which 12 weeks after admission had increased to 221 daily. However, it was stopped after prednisolone was administered (100mg daily). 7 months after starting the steroid treatment the collagen layer had disappeared and the villous atrophy had partially regressed. Over the next 6 months the prednisolone dosage was decreased to 10 mg daily. Shortly thereafter a perimembranous glomerulonephritis occurred, with proteinuria (up to 60 g/d) and oedema. It regressed to 6 g/d when the steroid dose was increased and cyclosporin, 0.5 g/d, had been added. On maintenance dosage of cyclosporin the histological and clinical remission of the collagenous sprue has now lasted for over 2 years. CONCLUSIONS: This case suggests that steroid administration is an effective treatment of collagenous sprue. The presence of diabetes and other immune-related diseases in this case also suggests that an immunological mechanism may play a causative role in collagenous sprue.

Anti-Inflammatory Agents↗
PubMed1995

Delineation of the dendritic cell lineage by generating large numbers of Birbeck granule-positive Langerhans cells from human peripheral blood progenitor cells in vitro.

It is well established by in vivo and in vitro studies that dendritic cells (DCs) originate from hematopoietic progenitor cells. However, the presumed intermediate of Birbeck granule (BG)+ Langerhans cells (LCs) has not been detected in cultures derived from bone marrow or peripheral blood progenitor cells (PBPCs), thus contrasting with the data obtained with cord blood. We show here that large numbers of BG+ LCs can be generated from human CD34+ PBPCs in vitro, when granulocyte-macrophage colony-stimulating factor and interleukin-4, potent promotors of LC/DC differentiation, are combined with a cocktail of early acting hematopoietic growth factors. LCs were found to emerge from CD33+CD11b+CD14- progenitor cells that they share with the monocytic lineage. During culture, these cells exhibited a sequence of dramatic morphologic changes, starting with a major increase in granularity followed by an increase in size herein exceeding that of all peripheral blood cells. At the same time, CD1a and major histocompatibility complex class II expression were upregulated and virtually all CD1a++ cells were BG+ by electron microscopy. With prolonged culture, CD1a was downregulated on a major population of cells, paralleled by a loss of BG and an increase of CD4, CD25, and CD80 expression that may correspond to the maturation of epidermal LC in vitro. However, these cells were consistently CD5- and did not exhibit changes in the CD45-isoform expression during culture. The availability of large numbers of these highly purified BG+ LCs and mature DCs allows for specific analysis of these subpopulations and provides a source of potent antigen-presenting cells from individual patients for vaccination protocols against infectious or tumor-associated antigens.

Antigen-Presenting Cells↗
PubMed1995

Interleukin 6 is essential for in vivo development of B lineage neoplasms.

Interleukin (IL) 6 has been suggested to be the major cytokine responsible for proliferation of neoplastic plasma cells in both human myeloma and mouse plasmacytoma. Much of the evidence supporting this suggestion is derived from in vitro studies in which the survival or proliferation of some plasma cell tumors has been found to be IL-6 dependent. However, it remains unclear whether this dependency is the consequence of in vivo or in vitro selective pressures that preferentially expand IL-6-responsive tumor cells, or whether it reflects a critical in vivo role for IL-6 in plasma cell neoplasia. To address this question, we have attempted to induce plasma cell tumors in normal mice and in IL-6-deficient mice generated by introduction of a germline-encoded null mutation in the IL-6 gene. The results demonstrate that mice homozygous (+/+) or heterozygous (+/-) for the wild-type IL-6 allele yield the expected incidences of plasma cell tumors. In contrast, mice homozygous for the IL-6-null allele (-/-) are completely resistant to plasma cell tumor development. These studies define the essential role of IL-6 in the development of B lineage tumors in vivo and provide experimental support for continued efforts to modulate this cytokine in the treatment of appropriate human B cell malignancies.

Alleles↗
PubMed1995

Transitional B cells are the target of negative selection in the B cell compartment.

B lymphocytes recognize antigen through membrane-bound antigen-receptors, membrane IgM and IgD (mIgM and mIgD). Binding to foreign antigens initiates a cascade of biochemical events that lead to activation and differentiation. In contrast, binding to self-antigens leads to death or to inactivation. It is commonly believed that the B cells acquire the ability to discriminate between self and nonself in the early phases of development. We report here that immature B cells, which have just emerged from the mIgMneg, B220pos pool, are not deleted upon binding of self-antigen. In vivo, developing B cells become sensitive to tolerance induction in a relatively late window of differentiation, when they are in transition from the immature (HSAbright, B220dull) to the mature (HSAdull, B220bright) stage. In the transitional B cells, early markers of differentiation such as Pgp1 (CD44) and ThB reach the highest level of expression, while the expression of CD23 and mIgD, late markers of differentiation, and expression of class II MHC, progressively increases. Most of the transitional B cells, but only few of the mature and of the immature B cells, express the fas antigen, while mature B cells, but not immature and transitional B cells, express bcl-2 protein. mIgM is present in low amounts in immature B cells, reaches the highest level of expression in transitional B cells and is down-regulated in mature resting B cells, where it is coexpressed with mIgD. The high expression of mIgM, the presence of the fas antigen and the absence of bcl-2 protein is compatible with the high sensitivity of transitional B cells to negative selection. In vitro, immature B cells die rapidly by apoptosis after cross-linking of mIgM. This result, combined with the resistance of immature B cells to elimination in vivo, suggests that early in development the stroma cell microenvironment modulates signals transduced through mIgM. The functional and phenotypic division of IgMpos bone marrow B cells in three compartments not only allows to define the target population of physiological processes like negative selection, but will also be a helpful tool for an accurate description of possible developmental blocks in mutant mice.

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

Efficient nonhomologous and homologous recombination in scid cells.

The severe combined immunodeficiency (scid) mutation affects both coding joint formation during immunoglobulin and T-cell receptor V(D)J recombination and double-strand break repair. We analyzed scid cells for their ability to undergo other types of DNA end joining: nonhomologous and homologous recombination. Using plasmid constructs carrying antibiotic resistance genes, we observed that the efficiency of nonhomologous integration in scid cells was equal to that in wildtype cell lines. In addition, there was no obvious difference in the fidelity of the integration and in the expression of the resistance genes. Moreover, scid cells were able to carry out homologous recombination of extrachromosomal substrates just as well as wildtype cells. These results suggest a mechanistic difference between nonhomologous integration and homologous recombination on the one hand and V(D)J recombination and double-strand break repair on the other.

Animals↗
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↗
PubMed1994

A lacZ-based vector system for the rapid detection of V(D)J recombinase activity.

Episomal vectors have been developed which are useful for studying V(D)J recombination both after transient transfections and in stably transfected cells. In contrast to recombination substrates previously described for transient assays, rearrangement of these vectors results in expression of beta-galactosidase which can be visualized directly in the transfected cell, shortening the time required for the assay to 1-2 days instead of 3-4 days. When these substrates are stably integrated into a preB cell line, subclones are found which show no beta-galactosidase staining, although the substrate is properly integrated, transcriptionally active and the transfectants still possess recombinase activity. This finding suggests that, at least in some chromosomal locations, transcription through a locus bearing recombination signal sequences is not sufficient for V(D)J recombination. Using these same vectors, we estimate that the frequency with which V(D)J recombination-negative preB variants arise is less than 10(-4) per generation.

Animals↗
PubMed1994

The IgM antigen receptor of B lymphocytes is associated with prohibitin and a prohibitin-related protein.

The two major classes of antigen receptors on murine B lymphocytes, mIgM and mIgD, are both contained in a complex with two additional molecules, Ig-alpha and Ig-beta, which permit signal transduction. Accordingly, early biochemical events after antigen binding to either receptor are similar; biological effects, however, are different. Here, we describe three newly discovered intracellular proteins of 32, 37 and 41 kDa molecular mass, that are non-covalently associated with mIgM, but not with mIgD. These proteins coprecipitate with mIgM in Triton X-100 and Nonidet P-40, but not in digitonin lysates. In addition, mIgM is to some extent associated with 29 and 31 kDa proteins that are predominantly associated with mIgD (see accompanying paper). Amino acid sequencing of p32 and p37 identified p32 as mouse prohibitin; this was corroborated by Western blot analysis with antibodies specific for rat prohibitin. p37 is a newly discovered protein. cDNA clones for both proteins were isolated and sequenced. The deduced amino acid sequence of p32 is identical to that of rat prohibitin. p37 is highly homologous to p32. Since prohibitin was identified as an inhibitor of cell proliferation, its association with mIgM, but not mIgD, could explain the different biological events elicited after engagement of each receptor.

Amino Acid Sequence↗
PubMed1994

Two new proteins preferentially associated with membrane immunoglobulin D.

The IgM and IgD classes of antigen receptor can perform different functions on B cells. However, so far no class-specific components communicating with the cytoplasm have been found in the two antigen receptors. We have employed a new biotinylation protocol to search for intracellular membrane Ig-associated proteins. Here we describe two proteins of 29 and 31 kDa that are associated with membrane IgD and to some extent with membrane IgM. The membrane IgM molecule is associated specifically with three proteins of 32, 37 and 41 kDa. The purification and sequencing of the two mIgD-associated proteins revealed that they are novel proteins which are related to each other. These proteins may be the missing link between the antigen receptor and the cytoskeleton and may contribute to functional differences between membrane IgM and membrane IgD.

Amino Acid Sequence↗
PubMed1994

Negative feedback regulation of IgE synthesis by murine CD23.

Immunoglobulin E is found in nanogram amounts in normal human and mouse serum. It is increased during parasitic infestations and mediates allergy. CD23, the low-affinity receptor for IgE (Fc epsilon RII), has been proposed as an important regulator of IgE synthesis. The type-II transmembrane lectin CD23 is expressed in the mouse on B cells and follicular dendritic cells. In humans there are two forms of CD23 which differ in their intracellular amino-terminal 6/7 amino acids; expression of the A-form corresponds to that of murine CD23, whereas the B-form is also found on T and other haematopoietic cells. CD23 has been implicated in cellular adhesion, antigen presentation, as a growth and differentiation factor for human B, T and plasma cells, and as a signal transduction molecule (reviewed in refs 3, 8). Here we disrupt the gene coding for murine CD23 (ref. 9) to clarify the role of CD23 in vivo and find that B- and T-cell development is normal in these CD23-deficient mice. Immune responses to the helminth Nippostrongylus brasiliensis are unaffected. In contrast, immunization with thymus-dependent antigens leads to increased and sustained specific IgE antibody titres compared with controls. Formation of germinal centres is normal. These results suggest that murine CD23 acts as a negative feedback component of IgE regulation.

Animals↗
PubMed1994

Two genes encoding ribosomal protein L3 of Schizosaccharomyces pombe and their proximal promoter regions.

We have cloned and sequenced two genes, rpl3-1 and rpl3-2, encoding the ribosomal protein L3 of Schizosaccharomyces pombe. The two genes contain an open reading frame encoding 388 amino acids (aa) with a M(r) of 43,808. The aa sequences are identical, except at position 78, where Rpl3-1 displays a valine residue and Rpl3-2 contains isoleucine. The aa sequences show 75% identity to the RPL3 aa sequence from Saccharomyces cerevisiae. S1-nuclease protection analysis revealed that both genes are transcribed. The promoter sequences of the two rpl3 genes are significantly different, but both promoters contain the conserved homol-D element. Transcription starts between 40 and 50 nt downstream from this element.

Amino Acid Sequence↗
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

A second promoter and enhancer element within the immunoglobulin heavy chain locus.

The joining of immunoglobulin gene segments during B cell development consists of a tightly regulated series of rearrangement steps. A variety of experiments have suggested that transcription is involved in activating the locus as substrate for the V(D)J recombinase. Here, we have characterized a region located immediately upstream of the most J-proximal D element (DQ52), which contains both promoter and enhancer activities preferentially active in precursors of B cells. Interestingly, this DQ52 regulatory element is inevitably deleted in fully rearranged H chain genes. We propose that it is involved in the early activation and rearrangement events at the IgH locus.

Animals↗
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

Characterization of a reovirus isolate from a rattle snake, Crotalus viridis, with neurological dysfunction.

A virus isolate from the brain of a rattle snake with central nervous system (CNS) symptoms was identified as a reovirus. The isolate did not agglutinate pig erythrocytes and was not neutralized by antisera against avian reovirus S1133 and mammalian reovirus type 3. The cytopathic effect in Vero cells was characterized by formation of syncytial giant cells. Electrophoretic analysis of the genome revealed 10 segments of dsRNA. The isolate displayed characteristics distinct from avian and mammalian reoviruses.

Animals↗