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H Eibel

Publications and source records attributed to H Eibel.

At least 37 records · Page 2Linked to original sources
PubMed1996

Pax1 is expressed during development of the thymus epithelium and is required for normal T-cell maturation.

Pax1 is a transcriptional regulatory protein expressed during mouse embryogenesis and has been shown to have an important function in vertebral column development. Expression of Pax1 mRNA in the embryonic thymus has been reported previously. Here we show that Pax1 protein expression in thymic epithelial cells can be detected throughout thymic development and in the adult. Expression starts in the early endodermal epithelium lining the foregut region and includes the epithelium of the third pharyngeal pouch, a structure giving rise to part of the thymus epithelium. In early stages of thymus development a large proportion of thymus cells expresses Pax1. With increasing age, the proportion of Pax1-expressing cells is reduced and in the adult mouse only a small fraction of cortical thymic stromal cells retains strong Pax1 expression. Expression of Pax1 in thymus epithelium is necessary for establishing the thymus microenvironment required for normal T cell maturation. Mutations in the Pax-1 gene in undulated mice affect not only the total size of the thymus but also the maturation of thymocytes. The number of thymocytes is reduced about 2- to 5-fold, affecting mainly the CD4+8+ immature and CD4+ mature thymocyte subsets. The expression levels of major thymocyte surface markers remains unchanged with the exception of Thy-1 which was found to be expressed at 3- to 4-fold higher levels.

Animals↗
PubMed1994

Transgene CD23 expression on lymphoid cells modulates IgE and IgG1 responses.

Transmembrane (m) and soluble (s) forms of CD23 perform activities related to various immune functions. Abnormal expression patterns of CD23 on lymphoid cells have been associated with certain pathologic conditions. To explore the effects of CD23 when it is overexpressed, on lymphoid cell development and immune function in vivo, transgenic mice were generated. These mice overexpressed either mCD23 or a 38-kDa molecular form of sCD23. Transgene expression under the control of Thy-1-regulatory sequences and the mouse Ig heavy chain enhancer (E mu) was prominent in thymus, spleen, bone marrow, and lymph nodes. Cells that expressed the transgenes included most thymocytes, peripheral CD4+ and CD8+ T cells, IgM+/highIgD-/low immature B cells, and IgMlowIgDhigh mature B cells. To resolve the expression pattern in the B cell lineage unambiguously, we used mice that carried a transgene and a disrupted endogenous CD23 gene simultaneously. Neither mCD23 nor sCD23 overexpression caused significant alterations in lymphoid cell maturation. In addition, basal serum levels of IgE and IgG1 proved to be normal. In three different experimental immune response paradigms, mCD23 transgenic, but not sCD23 and nontransgenic mice proved to be impaired in increasing serum levels of polyclonal IgE up to expected levels. In addition, mCD23 transgenic mice showed below normal increases of serum IgG1 levels in two of the three immune responses. In the presence of activated T cells and appropriate lymphokines, B cells from mCD23 mice secreted normal amounts of IgE and IgG1 in vitro, which suggests that there was no serious impairment of the T-B cell contact required for Ig production. In addition, there is no evidence for a significant role of mCD23 in IgE clearance. Therefore, we discuss alternative mechanisms by which mCD23+ B and/or T cells influence Ig production.

Animals↗
PubMed1994

Overexpression of zinc-finger transcription factor Z-225/Egr-1 in synoviocytes from rheumatoid arthritis patients.

In rheumatoid arthritis (RA) the proliferation of synovial lining cells appears to be one of the initial pathologic changes that contributes to the destruction of articular joints. To understand the pathomechanisms involved in these functional changes, we analyzed the transcriptional regulation of the zinc-finger gene 225 (Z-225/Egr-1), a transcription factor expressed in the immediate early events of cellular activation. We found that Z-225 transcripts were significantly up-regulated in RA synoviocytes. In primary and long term culture Z-225 was spontaneously transcribed at elevated levels. In situ hybridization of zinc-finger probe showed characteristic Z-225 transcripts in RA synovial tissues. Identity of these signals to the Z-225 gene product were confirmed in freshly isolated synovial tissue by enzymatic amplification of cDNA by the PCR technique. Z-225 transcripts were also detected and characterized in a cDNA library established from a RA synovial explant. We therefore conclude that RA synoviocytes spontaneously produce Z-225 gene products at elevated levels. Because early growth response gene Z-225 is involved in the regulation of expression of other genes such as proto-oncogenes c-ras and c-sis, which are also up-regulated in the RA synovium, activation of Z-225 transcription in RA may represent a key event in articular joint destruction.

Arthritis, Rheumatoid↗
PubMed1994

Mice deficient in CD23 reveal its modulatory role in IgE production but no role in T and B cell development.

To assess roles of CD23 in lymphocyte development and immune function in vivo, CD23-deficient mice (CD23-/-) were generated. Mice heterozygous with respect to the defective allele (CD23+/-) display 50% reduced levels of CD23 expression on CD23+ cell types. This pattern is consistent with a lack of parental or tissue-specific imprinting of the CD23 gene. Neither a 50% reduced level nor a complete lack of CD23 caused profound changes in lymphocyte compartments (thymocytes, peripheral T cells, and B-1 and B-2 B cells). The lack of CD23 also did not significantly alter in vitro the proliferative response of B cells triggered via the Ag receptor in combination with CD40 ligand, IL-2, and/or IL-4. Effects on polyclonal Ig production were tested in a Th2 cell-driven immune response in vivo after infection with Nippostrongylus brasiliensis, a parasite that dramatically enhances CD23 expression on B cells. In both primary and secondary immune responses, heterozygous CD23+/- mice developed slightly higher and CD23-/- mice similar serum IgE and IgG1 levels as compared with CD23+/+ (wild-type) mice. The increase in blood eosinophil counts was similar in all three types of mice. These findings show that after N. brasiliensis infection 1) a complete lack of CD23 in vivo neither prohibits nor significantly alters quantitatively polyclonal IgE levels in serum, and 2) a 50% reduction in cell-surface CD23 expression (CD23+/- mice) correlates with slightly increased serum IgE levels.

Animals↗
PubMed1992

Thymic hyperplasia in transgenic mice caused by immortal epithelial cells expressing c-kit ligand.

To dissect mechanisms that co-ordinate specific events in thymopoiesis we have characterized alterations in thymic structure and function caused by expression of a transgene. This gene encodes SV40Tag and is specifically expressed in a subset of thymic epithelial (TE) cells around birth. As a result the number of immortal TE cells increases, thymic mass increases (up to 3 g), and thymopoiesis is expanded. The latter is reflected by a approximately 100-fold increase of the major thymocyte subsets and increased peripheral T cell counts. Grossly hyperplastic thymi retain many but not all morphological features of a normal thymus. Also in grafts, SV40Tag+ TE cells steer expansion (up to 8 g) and organize a tissue with mainly cortex-like features that includes mainly SV40Tag+ TE cells, thymocytes, and macrophages. To investigate expression of specialized gene functions in the immortal TE cells, a cell line was derived. The Epi-A1 cell line expresses the genes for major histocompatibility complex class I and II, Thy-1, interleukin (IL)-6, IL-7, macrophage-colony-stimulating factor, and transforming growth factor-beta 3. Most importantly, Epi-A1 cells also express the IL-4 receptor and the c-kit ligand (KL), a factor that, in concert with commitment factors, channels progenitors into hemopoietic lineages. The expression of low constitutive levels of KL mRNA does not require IL-4, but KL mRNA levels are increased dramatically in response to IL-4. Since constitutive expression of KL mRNA in vivo is restricted to a small subset of TE cells in the thymus, our findings reveal a novel specific interaction between thymocytes and a specialized subset of TE cells.

Age Factors↗
PubMed1992

A survey of protein-DNA interaction sites within the murine immunoglobulin heavy chain locus reveals a particularly complex pattern around the DQ52 element.

The expression of immunoglobulin (Ig) genes is regulated at two levels: rearrangement of individual gene segments and transcription of continuous genes. To find transacting factors involved in mediating locus- and segment specific gene activation and expression, we surveyed a 3600-bp genomic region of the murine Ig heavy chain locus, spanning from the DQ52 element to the Ig heavy chain intron enhancer. We discovered nine, previously undescribed, protein-DNA complexes and estimated their individual binding-affinity preferences (Kr) by quantitative gel shift measurements. We observed one novel protein DNA interaction at the enhancer, two in the JH1 region and six within a 300-bp region immediately 5' to the DQ52 locus. The latter show a complex and specific binding pattern when comparing nuclear extracts derived from pre-B cells and fibroblasts. Further characterization of the interactions at the DQ52 locus by electron microscopy revealed the preferential formation of a protein complex binding to the DQ52 locus with pre B cell extracts. This behavior and the clustering of interaction sites 5' to the DQ52 element suggest that this region is involved in the regulation of heavy chain gene assembly.

Animals↗
PubMed1992

Transgenes encoding mutant simian virus 40 large T antigens unmask phenotypic and functional constraints in thymic epithelial cells.

Transgenes encoding simian virus 40 (SV40) T antigen (Tag) can cause hyperplastic or tumorigenic lesions of desired but also of unforeseen cellular origin. Unexpectedly the human growth hormone-releasing factor (GRF) gene promoter directs expression of SV40 Tag specifically in thymic epithelial (TE) cells. Expression starts in the neonate, in which GRF-Tag+ cells display strict numerical and spatial constraints. Tag supersedes mechanisms that constrain these features and GRF-Tag mice develop thymic hyperplasia. To characterize GRF-Tag+ TE cells and their putative normal counterparts we compared phenotypic and functional effects caused by transgenes encoding mutant large T antigens. This strategy is applicable to any situation in which T antigen is used to alter development. One large Tag mutant (K1 + 5080) does not cause thymic hyperplasia. GRF-Tag (K1 + 5080)+ TE cells display strict temporal and spatial constraints throughout life. TE cells expressing other mutant large T antigens that cause thymic hyperplasia do not obey these rules and reveal that phenotypically distinct GRF-Tag+ TE-cell stages exist in vivo. Analysis of conditional immortal GRF-Tag(tsA58)+ TE cells expressing a temperature-sensitive large Tag shows that large Tag blocks differentiation in these cells. Phenotype and functions in these cells are regulated by cellular differentiation and interleukin 4 (IL-4).

Animals↗
PubMed1991

B cell tolerance in mice transgenic for anti-CD8 immunoglobulin mu chain.

To analyze in vivo the induction of B cell tolerance against a T cell surface antigen, we generated transgenic mice expressing an anti-CD8.2 mu heavy chain gene. We show that self-specific B cells are efficiently tolerized if they express the membrane-bound form of the transgenic mu chain on their surface but that they can escape tolerization if they express only the secreted form. In the latter, we find an enhanced expression of anti-CD8.2 antibodies after polyclonal B cell activation. As a result, transgenic anti-CD8.2 antibodies bind to the CD8+ T cells but they did not induce their elimination. Furthermore, we observed the preferential expression of a limited subset of endogenous light chains with the transgenic mu chain. This suggests a positive or negative selection for particular heavy and light chain combinations in B lymphocytes.

Animals↗
PubMed1990

Non-tolerance and differential susceptibility to diabetes in transgenic mice expressing major histocompatibility class II genes on pancreatic beta cells.

In insulin-dependent diabetes mellitus aberrant expression of major histocompatibility complex (MHC) class II antigens might induce autoimmune destruction of insulin-producing pancreatic beta cells. Here we demonstrate that already the expression of single MHC class II chains (E alpha k and E beta b) is sufficient to cause diabetes without affecting beta cell morphology and cell numbers. Our transgenes interfere at least in two points of insulin production leading to a severely diabetic phenotype. In one case E beta b expression led to a 10-30-fold decrease of mouse insulin mRNA. In another case E alpha k expression reduced insulin secretion to background levels. In addition, we also found a patchy distribution of both insulin and E alpha k expression, indicating heterogeneity of the beta cell population, without the concomitant development of diabetes. Although the transgenic E alpha k E beta b MHC class II molecules were expressed on the surface of pancreatic beta cells, the transgenic mice did not prove to be tolerant for I-E antigen. Autoimmune reactions remained absent showing that aberrant MHC class II expression on pancreatic beta cells alone is not sufficient for the development of autoimmune diabetes in mice.

Animals↗
PubMed1989

Elimination of CD8+ thymocytes in transgenic mice expressing an anti-Lyt2.2 immunoglobulin heavy chain gene.

Individual T cell populations are characterized by specific surface proteins, namely by the T cell receptor complex (TCR) and by two accessory molecules, CD8 (Lyt2) and CD4 (L3T4). CD8 and CD4 are required for T cell interactions with class I or class II major histocompatibility complex molecules. In the thymus, immature CD8(-4)-TCR- cells differentiate, possibly via a short stage of CD8+4- thymocytes, into CD8+4+ TCR+ T cells and mature further into the main T cell populations, the CD8+4- TCR+ cytotoxic T lymphocytes and the CD4+8- TCR+ T helper cells. In order to analyse the differentiation steps involving CD8, we generated transgenic mice expressing mu heavy chain genes from an anti-Lyt2.2 hybridoma. Transgenic lines expressing either the complete (mu sm) or only the secreted mu protein (mu s) suffer from a severe depletion of their CD8+4+ thymocytes affecting also the mature CD8+4- and CD4+8- populations. The depletion is correlated to the expression of transgenic mu-chain proteins within thymocytes. This intrathymocyte expression of the mu chain prevents CD8-4- thymocytes from further differentiation, most probably via intracellular interactions between mu heavy chain and CD8 proteins. These results show that CD8 plays an important role during thymocyte maturation.

Animals↗
PubMed1984

Transcription from maize storage protein gene promoters in yeast.

Genes coding for zein storage proteins of maize of the 19 000- and 21 000-dalton size classes were integrated into chromosome II of the yeast Saccharomyces cerevisiae. Using the transformed yeast strains as an in vivo transcription system it was shown that promoter regions of the zein genes of both size classes were accurately recognized. In particular, the zein mRNA synthesis in yeast starts at the same nucleotide positions used in the maize endosperm. A difference in the promoter activity between the 21 000- and the 19 000-dalton zein genes was observed.

Cloning, Molecular↗
PubMed1983

Identification of the cloned S. cerevisiae LYS2 gene by an integrative transformation approach.

We isolated the LYS2 gene of S. cerevisiae on an autonomously replicating plasmid in a four-step procedure. First, we identified a recombinant plasmid which expressed a lys2 complementing activity upon yeast transformation of a lys2 mutant. Second, we determined the boundaries of the corresponding transcribed sequence in this plasmid by S1 nuclease mapping of the mRNA. Third, we inactivated the functional chromosomal copy coding for the lys2 complementing activity by directed integration of a plasmid that carried an internal fragment of the transcribed sequence. Fourth, we showed by a complementation test with an authentic lys2 mutant that the integration had inactivated the chromosomal LYS2 gene. This proved that the plasmid isolated in the first step indeed carried the LYS2 gene and not a suppressor of the lys2 mutation. The gene is unusually long (4.0 kb). It was used as hybridization probe in comparing LYS2 regions in various yeast strains and in a first construction of LYS2 based yeast vectors. Such vectors could be very useful because of the easy selection of lys2 mutants from any S. cerevisiae strain.

Amino Acid Oxidoreductases↗