Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The murine tumor line 70Z/3 resembles a pre-B lymphocyte in containing the heavy chain of IgM (mu) as a cytoplasmic protein in the apparent absence of light chain (L). However, these cells can be induced by lipopolysaccharide to differentiate into a B lymphocyte-like state, containing mu2L2 tetramers as membrane-bound molecules. This is a accompanied by an increase in mu synthesis, the acquisition of complex carbohydrate by mu, and the induction of L chain. We wished to determine which of these events is critical for membrane deposition of mu. We found that uninduced 70Z/3 cells, as well as lipopolysaccharide-uninducible variants, contained a low, constitutive level of membrane bound mu, all of which was found as mu2L2. Dextran sulfate, another inducing agent, apparently caused a redistribution of this pre-existing surface mu without altering the pattern of mu synthesis or processing. One lipopolysaccharide-uninducible variant showed a small subset of surface mu-positive cells, and the proportion of these cells increased with a prolonged induction period. The increase in mu synthesis was nearly normal, but mu did not acquire complex carbohydrate. However, the delayed appearance of surface mu-positive cells was paralleled by a delayed increase in L chain, which occurred only in those cells with mu on their membrane. We concluded that L chain signals the transport of mu to the cell surface.
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PMID:The requirement of light chain for the surface deposition of the heavy chain of immunoglobulin M. 640 41

To test the hypothesis that gamma 3 is the pivotal isotype for sequential heavy chain switching from mu to each of the gamma isotypes, we have compared the effects of anti-gamma 3 and anti-mu antibodies on the expression of immunoglobulin isotypes in lipopolysaccharide (LPS)-stimulated cultures of mouse spleen cells. IgM-, IgG1-, IgG2b- and IgG2a-containing plasma cells were enumerated by immunofluorescence and secreted immunoglobulins were measured by radioimmunoassay. Although anti-gamma 3 and anti-mu were equally effective in inhibiting the LPS-induced differentiation of IgG3 plasma cells, anti-gamma 3 had no effect on the differentiation of IgM, IgG1, IgG2b, or IgG2a plasma cells. These results support a direct mechanism of heavy chain immunoglobulin switching.
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PMID:Effect of anti-gamma 3 antibodies on immunoglobulin isotype expression in lipopolysaccharide-stimulated cultures of mouse spleen cells. 640 53

We have used a genetic approach to study the differentiation of B lymphocytes. The cultured murine cell line 70Z/3 resembles pre-B cells in containing the heavy chain of the immunoglobulin IgM, mu, as an internal protein in the absence of light chain, L. However, overnight incubation with the B cell mitogen lipopolysaccharide (LPS) induces the cells to mature to a B lymphocyte-like state by the induction of L chain synthesis and the appearance of IgM on the cell surface. We have used immunoselection against surface-bound IgM to isolate LPS uninducible variants of 70Z/3. These fall into two complementation groups, LPS A and LPS B. LPS A variants predominated and were found at a frequency of 1/1200. These cells were completely unresponsive to LPS. LPS B was represented by a single variant in which a subset of cells was induced to display wild-type levels of membrane-bound IgM, and the proportion of induced cells increased with prolonged incubation with LPS. We detected no structural defects in either variant group, but LPS B may represent a defect in the decision to differentiate in response to LPS.
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PMID:LPS-nonresponsive variants of mouse B cell lymphoma, 70Z/3: isolation and characterization. 641 57

Recent investigations have suggested that tissue-specific regulatory factors are required for immunoglobulin gene transcription. Cells of the mouse lymphocytoid pre-B-cell line 70Z/3 contain a constitutively rearranged immunoglobulin kappa light chain gene; the nucleotide sequence of this gene exhibits all the known properties of a functionally competent transcription unit. Nevertheless, transcripts derived from this gene are detectable only after exposure of the cells to bacterial lipopolysaccharide, implying that accurate DNA rearrangement is not sufficient to activate expression of the gene. Comparison of the sequence of the 70Z/3 kappa light chain gene with those encoding other immunoglobulin heavy and light chains has revealed that a distinctive promoter region structure is characteristic of this multigene family. The sequence A-T-T-T-G-C-A-T lies approximately 70 base pairs upstream from the site of transcriptional initiation in every light chain gene examined; in heavy chain genes, the corresponding location is occupied by the precise inverse (A-T-G-C-A-A-A-T) of this sequence. Although adjacent regions of DNA have diverged extensively in evolution, these octanucleotide sequences are stringently conserved at this location among diverse immunoglobulin genes from at least two mammalian species. The proximity of this conserved octanucleotide block to the site of transcriptional initiation suggests that it may serve as a recognition locus for factors regulating immunoglobulin gene expression in a tissue-specific fashion.
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PMID:Structure of the 5' ends of immunoglobulin genes: a novel conserved sequence. 642 35

The frequencies of lipopolysaccharide- (LPS) reactive B cells and their antibody specificity repertoire have been determined in the spleen and bone marrow (BM) of mice at different ages. A limiting dilution culture system was employed that allows the growth and development of every LPS-reactive B cell into a clone an IgM-secreting cells that are capable of switching to other Ig heavy chain isotypes (C gene expression). The secretion of IgM and IgG1 was assessed in the protein A plaque assay, whereas specific IgM antibody-secreting cells (V gene expression) were detected with the use of plaque assays specific for various heterologous erythrocytes and sheep red blood cells (SRBC) coupled with a number of different haptens. The frequencies of LPS-reactive B cells in the spleen and BM of C3H/Tif, C57BL/Ka, BALB/c, and CBA/Rij mice appeared to be similar in 6- to 12- and 100-wk-old animals, as was the switch frequency to IgG1 secretion in three strains tested. Moreover, no age-related changes were observed in the frequencies of antigen-specific B cells within the pool of LPS-reactive B cells in the spleen and BM of C57BL/Ka mice. The frequencies ranged from 1 in 10 to 1 in 20 for NIP4- and NNP2-SRBC, from 1 in 50 to 1 in 100 for TNP30-SRBC, and from 1 in 1000 to 1 in 4000 for SRBC, HRBC, and GRBC. The specificity repertoire of the "spontaneously" occurring ("background") IgM-secreting cells in the spleen and BM, on the other hand, did differ between young and old C57BL/Ka mice. During aging the frequencies of the tested specificities decreased in the spleen but increased in the BM. Our data indicate that in unintentionally immunized mice the clonal selection of B lineage cells by antigen takes place at the level of the mature, antigen-reactive B cell.
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PMID:Frequency analysis of functional immunoglobulin C and V gene expression in murine B cells at various ages. 660 47

The use of two polyclonal activators, dextran sulfate (DxS) and lipopolysaccharide (LPS), with or without the presence of additional antigen, is presented here as a system for exploring the antibody response of normal (naive) amd primed B cells. This system expands populations of cells not normally observed under in vivo regulation. By fusing such unnaturally activated B cells, anti-p-azophenylarsonate hybrids were produced that secrete different isotypes of antibodies. The frequencies of isotopes expressed by these hybrids may correspond to the chromosomal order of the heavy chain genes because greater numbers of IgM- and IgG3-secreting hybrids were produced than IgG2a hybrids. Only one IgA hybrid was observed. When DxS and LPS were used to stimulate antigen-primed B cells, hybrids were generated that simultaneously secrete two isotopes of antibody. These hybrids may represent a model of the antigen-stimulated maturational class-switch step observed in normal B cells that involves the expression of IgM and IgG isotypes by the same cell. Such hybrids offer an opportunity to study antibody regulation and diversity by examining the rearrangement of genes during the Ig switch, by exploring the nature of the necessary transitions of mRNA transcription and translation to produce functional antibodies, and by probing the structure and specificity of such antibodies.
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PMID:Antiarsonate antibody response: a model for studying antibody diversity. 680 26

M12.4, one of several B lymphomas derived from BALB/c mice, was mutagenized with ethyl methanesulfonate in vitro. M12.4.1, a subline of the mutant cells, was sensitive to hypoxanthine-aminopterin-thymidine selective medium and was fused with normal splenic B lymphocytes of C57BL/6ByJ mice. The hybridomas obtained from this fusion were shown to express mu heavy chain, H-2KbDb, Iad, and Iab on the cell surface by analyses of flow microfluorometry and a cytotoxicity assay, although parental M12.4.1 lacked mu heavy chain on the cell membrane. These results demonstrate that the B cell hybridomas with B cell surface antigens have been established in vitro. IgM molecules on the cell surface of the hybridomas were shown to originate from normal B cells of C57BL/6ByJ mice by flow microfluorometry analyses after staining with fluorescein-labeled Bet 1, a monoclonal rat antibody that recognizes Igh-6.5, a mouse IgM allotypic determinant. These hybridomas could generate IgM-secreting cells at the high frequency (more than 10% of the cultured cells) when stimulated with bacterial lipopolysaccharide. On the other hand, parental M12.4.1 did not develop any IgM-secreting cells under the same conditions. These findings suggest that these B cell hybridomas with B cell surface antigens may be a good model for the study of B cell differentiation.
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PMID:Establishment of B cell hybridomas with B cell surface antigens. 680 23

To determine whether the existence of anti-dsDNA producing lymphocyte clones is limited to autoimmune strains of mice, spleen cells derived from autoimmune mice (NZB, NZB X NZW F1, MRL) and from normal strains (BALB/c, DBA/2, C57BL/6, C3H/eb) were cultured with E. coli lipopolysaccharide (LPS). DNase-treated supernatants from these cultures were assayed for anti-dsDNA antibodies by employing a sensitive solid-phase radioimmunoassay with poly (dA-dT) as the antigen. All tested spleen cells secreted a small yet significant amount of anti-dsDNA upon stimulation with LPS. There was no difference in the amount or in the heavy chain type of anti-dsDNA secreted by cells from normal and autoimmune strain cells. Evidence of clonal expansion in unstimulated cells was observed only in cultures prepared from older autoimmune animals. Removal of T cells from the spleen cell preparations had no marked effect on the spontaneous or stimulated antibody secretion. Anti-dsDNA antibodies could also be induced in vivo by i.p. injection of LPS into young normal animals. Splenocytes from all tested strains spontaneously secreted anti-ssDNA and anti-TNP antibodies in culture, and these were present at relatively high levels in the serum of unstimulated animals. Stimulation with LPS increased secretion of anti-ssDNA and anti-TNP in all strains in vitro and in five of seven strains in vivo as well. It can be concluded that a) the existence of anti-dsDNA-producing clones is not limited to autoimmune strains, and b) these clones are expanded in old but not in young autoimmune mice. They are not expanded in normal mice at any age.
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PMID:The in vitro and in vivo induction of anti-double-stranded DNA antibodies in normal and autoimmune mice. 697 78

To execute different biological functions, the expression pattern of immunoglobulin heavy chain genes (IgH) is altered during B lymphocyte differentiation. Early in B cell differentiation, it is assumed that the heavy chain promoter and the intragenic enhancer (E mu) ensure VDJ recombination. This leads to the expression of the immunoglobulin receptor on the cell surface. An additional strong enhancer in the far 3' end of the IgH locus has, however, prompted a re-evaluation of the regulation of immunoglobulin gene expression. To define the temporal and spatial regulation of the IgH 3' enhancer, transgenic mice harboring an enhancer-dependent reporter gene construct were generated. Here we demonstrate that IgH 3' enhancer activity is largely restricted to activated immunocompetent B cells. Furthermore, the enhancer can be transactivated following mitogen stimulation with lipopolysaccharide and 12-O-tetradecanoylphorbol 13-acetate. We propose a model whereby 3' enhancer activation is linked to the activation of resting immunocompetent B cells. The implications of the enhancer being active in late B lymphocyte differentiation, when heavy chain class switching occurs, are discussed.
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PMID:Lipopolysaccharide-dependent transactivation of the temporally regulated immunoglobulin heavy chain 3' enhancer. 751 78

The rate of germ-line RNA transcription correlates with the rate of immunoglobulin heavy chain isotype switching. A promoter element for the transcription of RNA from the germ-line mouse immunoglobulin epsilon heavy chain constant region gene is induced by interleukin(IL)-4 and lipopolysaccharide, and is bound at its transcription initiation sites by an IL-4-inducible nuclear protein, NF-BRE. To examine the function of the binding site for this IL-4-inducible complex, substitution mutations were introduced in the promoter. These binding site mutations increased promoter activity and decreased binding of NF-BRE. To investigate the paradox of an IL-4-inducible protein binding to a repressor site in an IL-4-inducible promoter, we determined that the non-histone chromosomal protein HMG-I(Y) binds at the transcription initiation sites of the germ-line epsilon promoter. Assays with antisera against HMG-I(Y) revealed monomeric HMG-I(Y) in nuclear extracts. Cotransfection of an expression construct directing the synthesis of anti-sense HMG-I(Y) RNA also increased promoter activity, consistent with a repressor function of HMG-I(Y). Thus, the data are most consistent with a model in which HMG-I(Y) participates in repression of promoter activity. The effects of IL-4 may include derepression at this site.
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PMID:The non-histone chromosomal protein HMG-I(Y) contributes to repression of the immunoglobulin heavy chain germ-line epsilon RNA promoter. 770 11


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