Biomedical subjects

K U Hartmann

Publications and source records attributed to K U Hartmann.

At least 19 recordsLinked to original sources

PubMed2000

Global analysis of gene expression in cells of the immune system II. Cell-free translation products and high-density filter hybridization data.

We have developed an experimental system for linking information on cell-free transcription and translation products from cDNA clones with data obtained from hybridization signals from complex probes. The work described in this paper consists of two distinct processes, one being the construction of a system of clonal addresses and the other the identification of expressed genes involved in the studied processes. We describe the use of this system to identify genes involved in thymus development. Complex probes from fetal thymuses (GD15, 17 and newborn) of Balb/c mice were used to identify genes, which are up- or downregulated during the process of differentiation. The full set of information is available in the Clone-base of the Basel Institute for Immunology and will be retrievable from the website of the collaborating laboratories.

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PubMed1997

Detection of Fas and its ligand, FasL, in mouse thymus by in situ hybridization.

Part of the apoptotic process in lymphocytes involves the Fas receptor, which can transduce a cell death signal after interaction with its ligand, FasL. Many studies concerning expression of Fas and FasL in the thymus have been performed, but no detailed information about in situ expression patterns of mRNA inside the thymus is available. In the present study the expression of Fas and FasL was evaluated by non-radioactive in situ hybridization in the thymi of normal mice and compared with the results of lpr- and gld-mice, the two mouse models with mutations of Fas and FasL, respectively. In the thymi of normal and gld-mice, Fas mRNA was found only in the medulla. In lpr-mice, no Fas mRNA expression could be detected. The expression pattern changes as the mice get older. No specific signals for FasL mRNA were detected in any of the mice (normal, lpr, gld) tested. Together, these results are consistent with absence of a role for the Fas-FasL interaction in thymocyte apoptosis.

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PubMed1996

Protein expression during murine thymus differentiation.

Driven by our long-standing interest in identifying proteins of the immune system and in characterizing processes involved in lymphocyte differentiation, we studied protein expression in biosynthetically labeled fetal and newborn thymus by 2D gel electrophoresis. Autoradiographs of the gels were scanned with a densitometer and image analysis was performed using the Kepler system. Calibrated polypeptide spot abundances (volumes) were compared to assesses qualitative and quantitative changes of the spot volumes. Among over 300 proteins evaluated at GD (gestation day) 13, 15, and 17, there were sets of proteins that increased and other that decreased in intensity. We could in addition recognize proteins that were completely absent at GD 13 and/or 15 and that appeared thereafter to gradually increase in intensity. Conversely, various polypeptide spots present at early stages (at GD 13 and 15) disappear later (at GD17 or at birth). Among the proteins that increase in intensity prevail molecules with masses less than 35 kD, whereas a considerable portion of those that decrease in intensity are characterized by masses above 60 kD. Spots reported in this communication were not defined beyond tagging them with numbers, which is a prerequisite to follow them up in the proteinpaedia developed in our laboratory. The next step will be to retrieve the coding sequences from the existing partitioned cDNA library (BW 5147) as well as from thymocyte subtraction libraries. We predict that among those polypeptides with varying intensity, important regulatory proteins in thymus development will be found.

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PubMed1995

Loss of Fas/Apo-1 receptor accelerates lymphomagenesis in E mu L-MYC transgenic mice but not in animals infected with MoMuLV.

The Fas/Apo-1 receptor is an integral membrane protein that transduces apoptotic signals upon binding to its natural ligand or to specific antibodies. Loss of Fas/Apo-1 receptor leads in (lpr,lpr) mice to a nonmalignant accumulation of abnormal T-cells very probably due to the lack of induction of apoptosis in peripheral T-cells. It has been reported that soluble forms of Fas/Apo-1 receptor that may interfere with apoptotic signaling occur in patients suffering from various forms of lymphoid neoplasms. Therefore, we wished to investigate whether the loss of proper homeostatic regulation through Fas/Apo-1 receptor mediated apoptosis could influence the process of lymphomagenesis. To this end, we performed two experiments (i) we infected (lpr,lpr) animals with Moloney Murine Leukemia Virus (MoMuLV) that causes T-cell lymphoma in mice and (ii) we crossed (lpr,lpr) animals with E mu L-myc transgenic mice that are prone to develop T- and B-cell lymphoma due to deregulated expression of the L-myc transgene by the immunoglobulin enhancer E mu. We find that infection with MoMuLV did not accelerate the formation of lymphoid neoplasms in (lpr,lpr) mice when compared to infected normal animals. However, E mu L-myc/(lpr,lpr) animals that constitutively express the L-myc transgene in the lymphoid lineage clearly show accelerated formation of T- and B-cell lymphoma when compared to normal E mu L-myc transgenics. These data demonstrate that in cooperation with particular oncogenes impairment of Fas/Apo-1 receptor function can indeed affect and modulate the process of tumor formation.

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PubMed1995

Interactions of B6 wild and B6 gld cells engrafted within athymic nude beige recipients.

The murine gld mutation is targetted to the gene coding for the ligand of the Fas receptor for apoptosis. Gld mice display a lymphoproliferative and autoimmune syndrome that can be transferred in both irradiated euthymic wild and athymic beige (nubg) recipients. In order to test whether a supply of normal wild cells could correct the development of the gld syndrome, nubg mice were grafted with mixtures of gld and wild spleen cells from congenic donors which differed for the allotypes of the T-cell Thy1 membrane glycoprotein and/or of the B-cell Ig heavy chain. In the nubg chimeras, the wild spleen cells could down-regulate the hyperactivation of the B cells and the proliferation of the gld T cells, but this was not due to total eradication of the gld T-cell subset. Since this occurred in an athymic recipient, the correction of the gld syndrome did not require wild stem cell differentiation within a thymic environment, but should only depend on a sufficient Fas ligand supply by normal wild cells. Since the gld cells could proliferate in the nubg environment, the nubg environment could not provide sufficient Fas ligand to regulate the gld cell proliferation. Thus, the nubg B cells might lack Fas ligand expression, or express it but to a lower extent that T cells.

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PubMed1995

Development of grafted gld cells in athymic and euthymic recipients.

Mice homozygous for the gld (generalized lymphoproliferative disease) and lpr (lymphoproliferation) mutations display similar autoimmune and lymphoproliferative diseases. Both result from defective apoptosis, the targets of the lpr and gld mutations being the genes for, respectively, an apoptosis-signalling receptor [the Fas antigen receptor (FasR)] and its counter-receptor [the Fas ligand (FasL)]. Though this definitely causes the development and accumulation of large numbers of unusual Thy-1+ B220+ cells in peripheral lymphoid organs, details on how this actually occurs are still lacking. Whether differentiation of gld T cells into Thy-1+ B220+ cells might depend on the environment was analysed by phenotyping the cells which expanded in four different immunodeficient environments (nubg, nulpr, scid and scidbg). Though all four types of congenic chimeras developed hyperglobulinaemia, autoimmunity and a lymphoproliferative disease, substantial differences were found for the athymic and euthymic chimeras. In the athymic gld chimeras, the lymphoproliferation concerned all cell subsets, whereas in the euthymic gld chimeras it was, as in gld mice, due to the accumulation of cells of the Thy-1+ B220+ subset. Thus, the gld T cells could proliferate without differentiating into the Thy-1+ B220+ subset, but this depended on the nature of the environment. Furthermore, emergence of a gld syndrome in these four environments would suggest that B cells and stromal cells do not express FasL, at least in levels sufficient to compensate for the deficiency of the grafted gld cells.

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PubMed1994

The Yaa mutation induces the development of autoimmunity in mice heterozygous for the gld (generalized lymphadenopathy disease) mutation.

Mice homozygous for either the generalized lymphoproliferative disease (gld) or the lymphoproliferation (lpr) nonallelic mutations develop similar syndromes combining systemic autoimmunity and lymphoproliferative disease. Though essentially recessive, the lpr and gld mutations may be expressed in the heterozygous state: [lpr/+] mice displayed a mild "lpr-like" autoimmunity, and the [lprcg/+ gld/+] mice developed a "gld-like" disorder, showing interactions of the gld gene product with the nonallelic lprcg product. The Y-chromosome-linked autoimmune accelerator (Yaa) mutation being an autoimmunity accelerator, its association with an heterozygous gld gene might also bring a gld-like syndrome. The [gld/+ Yaa] mice were shown here to develop autoimmunity and splenomegaly like [gld/gld] mice, but without their typical lymphadenopathy. Furthermore, the [gld/+ Yaa] splenomegaly was not due to the expansion of the unusual Thy1+ B220+ T-cell subset typical of the gld syndrome, but rather to a polyclonal expansion of the major lymphoid cell subsets. Thus, the syndrome shown by [gld/+ Yaa] mice was not a gld-like syndrome. This suggests that the interactions of the gld gene product with the Yaa product and with the lprcg product must be different.

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PubMed1994

The Yaa gene-dependent B-cell deficiency worsens the generalized lymphadenopathy and autoimmunity of C57BL/6-gld male mice.

The BXSB mice are unique among murine models for systemic lupus erythematosus in that males are much more severely affected than females. The BXSB male disease is associated with a Y-chromosome-linked gene, which is an autoimmunity accelerator gene (Yaa). The Yaa mutation affects the B-cell subset, which becomes hyper-responsive to T-cell signals. The Yaa mutation was combined to the generalized lymphadenopathy disease (gld) gene in order to know whether an additional intrinsic B-cell defect might enhance gld disease in the male mice. The B6-gld-Yaa male mice were shown to display earlier and exacerbated lymphoproliferative and autoimmune features. It appeared that the milder gld syndrome observed in B6-gld male mice with a normal Y-chromosome was dependent on the mechanisms of B-cell activation and that the B cells could also accelerate the lymphoproliferation and the differentiation of T cells into Thy-1+ B220+ cells.

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PubMed1993

Expression of a Pim-1 transgene accelerates lymphoproliferation and inhibits apoptosis in lpr/lpr mice.

Transgenic mice expressing the Pim-1 kinase are predisposed to develop T-cell lymphomas with a long latency period of about 7-9 months. However, the exact functional basis of the oncogenic activity of Pim-1 remains obscure. C57BL/6 mice homozygous for the lpr mutation develop a well-described lymphoproliferative syndrome at about 26-30 weeks of age. This syndrome is characterized mainly by the accumulation of abnormal T cells in lymph nodes because of the lack of Fas receptor-induced apoptosis. We find that backcross of E mu-Pim-1 transgenics (mice with a transgene that carries the mouse Pim-1 gene under the transcriptional control of the immunoglobulin heavy chain gene enhancer E mu) into lpr/lpr mice results in strong acceleration of lymphoproliferation and dramatic enlargement of lymph nodes. In addition, we show here that cultured lymph node cells from E mu-Pim-1 lpr/lpr mice are rescued from rapid apoptosis that normally occurs in nontransgenic lpr cells in vitro. We also present evidence that CD4+/CD8+ double-positive thymocytes from lpr/lpr mice are sensitive to dexamethasone-induced apoptosis, although lpr/lpr mice lack the Fas receptor. In contrast, E mu-Pim-1 lpr/lpr animals show considerable protection from dexamethasone-induced apoptosis. These results show that Pim-1 can strongly accelerate lymphoproliferation through inhibition of apoptosis and thereby provide first insight into the functional basis for the oncogenic activity of Pim-1.

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PubMed1992

Profound block in thymocyte development in mice lacking p56lck.

The protein Lck (p56lck) has a relative molecular mass of 56,000 and belongs to the Src family of tyrosine kinases. It is expressed exclusively in lymphoid cells, predominantly in thymocytes and peripheral T cells. Lck associates specifically with the cytoplasmic domains of both CD4 and CD8 T-cell surface glycoproteins and interacts with the beta-chain of the interleukin-2 receptor, which implicates Lck activity in signal transduction during thymocyte ontogeny and activation of mature T cells. Here we generate an lck null mutation by homologous recombination in embryonic stem cells to evaluate the role of p56lck in T-cell development and activation. Lck-deficient mice show a pronounced thymic atrophy, with a dramatic reduction in the double-positive (CD4+CD8+) thymocyte population. Mature, single-positive thymocytes are not detectable in these mice and there are only very few peripheral T cells. These results illustrate the crucial role of this T-cell-specific tyrosine kinase in the thymocyte development.

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PubMed1989

Differentiation of epithelial stroma during ontogenesis of the thymus in mice: a speculation on the origin of the thymus as a sensory organ.

Two monoclonal antibodies recognizing subpopulations of epithelial stroma cells of the embryonic mouse thymus are described. Antibody Th-115/7 reacts with epithelial cells of the thymus cortex: antibody Th-101/5 binds to stroma cells of the thymus medulla. In cryosections of whole embryos Th-115/7 bound in addition to mucosal epithelial cells of the pharynx, of the Th-101/5 stained submucosa cells of various regions of the pharynx, of the cavum nasi, of the tongue etc. These observations are compatible with the hypothesis that the thymus anlage originally had developed as a sensory organ at the entrance of the pharynx before it became a primary lymphoid organ.

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PubMed1989

Monoclonal antibodies generated against activated B-cells: unexpected specific reactivity to T-cells.

Monoclonal antibodies (Mabs) were produced against C57B1/6 "nude" lymphoblast cells. They are IgG2a and do not react with mouse serum proteins. Five Mabs were characterized functionally by immunohistochemistry and immunofluorescence in spleen, lymph nodes and Peyer's patches from nude and normal mice, and normal mouse thymus. Two Mabs reacted with regions containing B-cells as indicated by immunoperoxidase staining, another recognized T- and B-cell sites and two specifically stained T lymphocyte-containing areas. Immunofluorescence studies confirmed the sites identified above by immunohistochemistry.

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PubMed1988

Successive changes of the cellular composition in lymphoid organs of MRL-Mp/lpr-lpr mice during the development of lymphoproliferative disease as investigated in cryosections.

To analyze the tissue distribution of lymphocyte subsets of autoimmune MRL/Mp-lpr/lpr mice, we have studied cryostat sections of the lymphoid organs at different stages of the disease using monoclonal antibodies directed against Ly 1 (MAb 53-7.3), Ly 2 (MAb 53-6.7), B 220 (MAb 14.8), and mu heavy chain (MAb b.7.6). We have observed an increase of a characteristic subpopulation of lymphocytes (Ly 1+ (dull), Ly 2-, B 220+, sIgM-), first seen at age of 8 weeks. In lymph nodes, these cells are first organized follicle-like with sIgM+ cells in the center. Later (20th-29th weeks), mu+ cells are found almost exclusively in small areas between the follicles. In the spleen, the cells first appear in the outer periarteriolar lymphatic sheath. Later, they are distributed within the follicles. sIgM+ cells disappear from the follicles; few remain within the marginal zone. In the thymus, some mice show a highly increased number of mu+ cells in the medulla. In Peyer's Patches, these Ly 1+ (dull) B 220+ cells are found predominantly in the interfollicular zone.

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PubMed1984

Induction of resting B cells to DNA synthesis by soluble monoclonal anti-immunoglobulin.

A novel monoclonal anti-immunoglobulin is described which in soluble form is comparable to lipopolysaccharide in its ability to induce DNA synthesis in populations of resting B cells. It inhibits lipopolysaccharide-induced B cell maturation to immunoglobulin secretion while not suppressing mitogen-induced proliferative responses. B cells from C3H/HeJ mice are stimulated as well as those from C3H/Tif mice demonstrating that the induction capacity of this monoclonal antibody does not involve functional lipopolysaccharide receptor molecules.

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PubMed1983

Immunoperoxidase slide assay (IPSA)--a new screening method for hybridoma supernatants directed against cell surface antigens compared to other binding assays.

A modified immunoperoxidase assay on microscope slides (IPSA) was adopted as a screening procedure for hybridoma supernatants with specificity for human lymphocyte subpopulations. The method proved to be suitable for testing a large number of hybridomas with a minimum of cells and reagents. In addition, the slide-technique yields considerable information about the type and morphology of target cells. This allows a first differentiation between cell types in the assayed preparation, e.g. between lymphocytes and monocytes. Compared to indirect immunofluorescence, solid-phase radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) with intact cells as antigen, IPSA turned-out to be as sensitive as RIA and superior to indirect immunofluorescence and ELISA. Nevertheless, none of the assays used detected all supernatants binding to cells in the right manner and could, thus, be considered ideal. In our hands, the combination of RIA and IPSA proved to be an excellent system for screening procedures on lymphocytes.

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PubMed1982

A new murine cell surface differentiation antigen (Leugp90) defined by a rat monoclonal antibody: cellular distribution and biochemical characterization.

Monoclonal antibodies to murine lymphocyte differentiation antigens were generated by fusing the mouse myeloma cell line X63-Ag8.653 with spleen cells derived from Lewis rats hyperimmunized with lymphoid cells from nude (C57BL/6) mice. One of these antibodies--designated 3MB1--recognizes a previously undescribed cell surface antigen. This antigen is expressed on 62% of spleen cells, 9% of thymus cells, and 98% of peritoneal macrophages. Virtually all LPS- and Con A-induced lymphoblasts carry this newly found antigen. The 3MB1 determinant is limited in its expression to leukocytes. It is not found in other tissues such as brain, liver, kidney, or on erythrocytes. Biochemical analysis reveals that the 3MB1 target antigen consists of a single chain glycoprotein with an approximate m.w. of 90,000.

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PubMed1981

The effect of whole body heat exposure and of cooling the hypothalamus on antibody titre in the rat.

In rats implanted with chronic hypothalamic thermodes and immunized with sheep erythrocytes, body temperature was increased, 4 h per day for 2 weeks, either by exposing the animals to external heat or by cooling the preoptic area. The titre of antibodies against sheep erythrocytes was nearly tripled by preoptic cooling but was drastically decreased by heat exposure. These opposing effects of active and passive increases in body temperature indicate that factors other than the change in body temperature must also have played a significant role in modifying the humoral immune response.

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PubMed1975

Stimulation of murine B lymphocytes by isolated C3b.

Addition of isolated B3b to murine lymph node cell cultures induced increased DNA synthesis. The stimulation is dependent on the dose of C3b added and is potentiated by fetal calf serum present in the medium. Isolated C3 is less stimulatory than C3b; C3a and C3c had no effect on DNA synthesis in these cultures. 10-20% large immunoglobulin containing blastlike cells developed in lymph node cell cultures stimulated by 50 mug C3b in the presence of 3% fetal calf serum. The stimulation by C3b was observed in cultures of lymph node and spleen cells of several mouse strains including C3H/HeJ and congenitally thymus-deficient (nu/nu) mice. The results suggest that B lymphocytes are the main target of the stimulatory effect of C3b. Two mechanisms which may be involved in the stimulation of lymphocytes by C3b are discussed: (a) cross-linking of receptors on the cell surface or between cells, and (b) the binding of C3b to receptors of B lymphocytes and the formation of the complement enzyme C3bB. The results are compatible with the suggestion that activation of C3 is part of the events triggering the B lymphocytes.

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