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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have developed a sensitive polymerase chain reaction assay for measuring the fraction of rearranged immunoglobulin kappa genes in a cell population. Using this assay with Abelson virus-transformed murine pre-B cells, we have found that bacterial lipopolysaccharide treatment, which activates transcription of the unrearranged kappa constant region gene, also activates kappa gene rearrangement. In addition, we have been able to detect kappa gene rearrangement in cell lines that do not produce a functional heavy chain gene product (mu protein). These results implicate transcription or transcription factor binding as a regulator of immunoglobulin gene rearrangement.
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PMID:Activation of immunoglobulin kappa gene rearrangement correlates with induction of germline kappa gene transcription. 250 32

The murine B cell lymphoma I.29 contains cells expressing surface IgM or IgA with identical heavy chain variable regions (9, 25, and D. Klein and J. Stavnezer, unpublished data). Purified IgM+ cells from the lymphoma have been adapted to culture and induced to switch to IgA, IgE, or IgG2 by treatment with lipopolysaccharide (LPS) or by treatment with a monoclonal anti-I.29 antiidiotype plus LPS. Clones of IgM+ cells have been obtained and induced to switch. Under optimal conditions, 30% of the cells in the culture expressed IgA 8 d after the inducers were added, and by 15 d 90% of the cells were IgA+. In actively switching cultures, up to 50% of the cells whose cytoplasm stained positively with anti-IgA stained simultaneously with anti-IgM, which indicates that the appearance of IgA+ cells in the cultures was due to isotype switching and not to clonal outgrowth. Examination by Southern blotting experiments of the Ig heavy chain genes in I.29 cells before and after switching revealed that isotype switching was accompanied by DNA recombinations that occurred within or immediately 5' to the tandemly repeated switch sequences. Within 3 d after the addition of inducers of switching, the nonexpressed chromosome underwent a variety of deletions or expansions within the S mu region, and a portion of the S alpha regions had undergone a 0.9-kb deletion. In cultures that contained at least 12% IgA+ cells, rearranged, expressed alpha genes, produced by recombination between the S mu region within the expressed mu gene and the S alpha region, were detected.
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PMID:Induction of immunoglobulin isotype switching in cultured I.29 B lymphoma cells. Characterization of the accompanying rearrangements of heavy chain genes. 257 86

The unassembled (soluble) and assembled (particulate) pools of clathrin in murine lymphocytes have been separated by centrifugation, and specifically quantified by immunoblotting of cellular extracts with an anticlathrin heavy chain monoclonal antibody. In resting spleen lymphocytes only 25-30% of the total cellular clathrin was found to be present in an assembled form. Upon activation of lymphocytes with B or T cell mitogens (lipopolysaccharide or concanavalin A), the levels of assembled clathrin increased to 60% of the total. These changes in the levels of assembled clathrin were not due to an increase in total cellular clathrin concentration following lymphocyte activation, but rather to changes in the steady state ratio of assembled to unassembled clathrin. The increase in assembled clathrin preceded the expression of transferrin receptors, as measured by the cell surface binding of an antitransferrin receptor monoclonal antibody, and maximal DNA synthesis, indicating that clathrin assembly occurs early after lymphocyte activation and precedes cell division. Immunofluorescence analysis of activated lymphocytes with an anti-clathrin heavy chain monoclonal antibody revealed a punctuate staining pattern characteristic of coated pits and vesicles. Activated B lymphocytes displayed particularly prominent staining in the perinuclear region compared to T cells, suggesting that clathrin assembly may be important for B cell functions such as immunoglobulin synthesis or secretion. These results suggest that in lymphocytes, clathrin assembly is a dynamic process that is triggered by mitogenic stimuli.
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PMID:Increased assembly of clathrin occurs in response to mitogenic activation of murine lymphocytes. 266 60

A method for in situ hybridization has been developed which detects immunoglobulin-specific mRNA transcripts in single murine B lymphocytes with radiolabelled, immunoglobulin gene-specific single-stranded DNA probes. The method has been applied to myeloma and hybridoma cells and to B lymphocytes at various stages of their maturation from small, resting B cells to Ig-secreting plasma cells. A critical step in the procedure is the treatment of the cells with pronase. The various cell types have been found to be differently susceptible to this treatment. Single-stranded DNA probes of different lengths, i.e., between 26 and 1000 bp, have been employed in the hybridization. The number of silver grains over a cell increases proportionally with the length of the probe and with its concentration in the hybridization reaction. The kinetics of the increase of mu-heavy chain-specific RNA molecules in single cells and the appearance of 'switched', gamma-heavy chain-expressing cells are shown after stimulation of murine B cells with lipopolysaccharide.
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PMID:In situ hybridization of immunoglobulin-specific RNA in single cells of the B lymphocyte lineage with radiolabelled DNA probes. 300 20

A monoclonal antibody (mAb) G-5-2 was isolated which binds to transformed as well as normal cells of the B lineage but not to cells of the T cell, myeloid lineages nor to fibroblasts. mAb G-5-2 reacts with pre-B and plasma cell-transformed lines, and it preferentially recognizes normal pre-B cells from fetal liver and bone marrow as well as plasma cells from spleen of mice. G-5-2+ fetal liver cells isolated by cell sorter express mRNA for mu heavy chain Ig gene and generate in vitro antibody-producing cells when co-cultured with lipopolysaccharide and rat thymocyte filler cells. During development the frequency and staining intensity of G-5-2+ cells in fetal liver from normal mice increases from 1% G-5-2+ cells at day 14 to approximately 7% positive cells at day 18 of gestation. Several strains or normal mice contain comparable numbers of G-5-2+ cells as well as B-220+ and BP-1+ B cell precursors in the fetal liver. Mice carrying the xid mutation have 3-4-fold less G-5-2+ as well as B-220+ and BP-1+ cells in the fetal liver, suggesting that the effects of the xid mutation may be manifested from early stages of B cell development. Fetal liver cells from mice carrying the scid mutation were found to contain normal numbers of G-5-2+ as well as B-220+ and BP-1+ pre-B cells. These results indicate that differentiation from progenitors to pre-B cells in scid mice may occur normally; the scid mutation would thus appear to affect the process of rearrangement and expression of the Ig genes in the developing pre-B cells. mAb G-5-2 precipitates a 76-kDa glycoprotein from surface-radiolabeled pre-B cells and plasma cells. Taken together, these results indicate that G-5-2 mAb recognizes a novel B cell lineage-specific surface molecule called PB76 which is preferentially expressed by pre-B cells and plasma cells.
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PMID:PB76: a novel surface glycoprotein preferentially expressed on mouse pre-B cells and plasma cells detected by the monoclonal antibody G-5-2. 306 Mar 63

We describe here a murine Ly-1-bearing pre-B-cell tumor that, when induced for kappa light chain expression with bacterial lipopolysaccharide, also gives rise spontaneously to a few percent of cells expressing surface lambda light chains. These lambda-positive cells have undergone DNA rearrangements involving either V lambda 1 or V lambda 2 genes. Nearly all clones of lambda-bearing cells express mu and lambda on their surface (but not kappa). However, all these lambda-positive clones continue to transcribe kappa mRNA and synthesize internal kappa chains. Further, surface lambda-positive clones show JH rearrangements on one or both heavy chain chromosomes.
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PMID:Frequent lambda light chain gene rearrangement and expression in a Ly-1 B lymphoma with a productive kappa chain allele. 308 97

The property of lipopolysaccharide to induce B cells to both proliferate and differentiate to IgM, IgG3 and IgG2b expression can be ascribed either to a precommitted sequence of molecular events in the activated B cells or, alternatively, to separate activities which independently modulate the two events. To discriminate between these two possibilities we have investigated the relationship between the doses of the polyclonal stimulus and the commitment of the activated cells to proliferate and to produce various isotypes. Low doses of ligand supported proliferation as well as IgM but not IgG2b secretion. On the contrary, high doses of the same ligand were less efficient in supporting proliferation but strongly induced heavy chain class switch. The effect of lipopolysaccharide concentrations on CH genes expression decayed with the distance from mu to the respective C gamma gene. Although we could define different B cell subsets on the basis of their proliferative response to various doses of the ligand, all these B subpopulations were found to be multipotential in terms of their switching capacity. Taken together our data show that in lipopolysaccharide cultures B cell proliferation and heavy chain switch are two events completely dissociable on the basis of their inducing requirements.
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PMID:The commitment of secretory cells to the selective expression of immunoglobulin CH genes is determined by the available concentrations of the triggering ligand. 308 79

Mouse B lymphocytes can be activated polyclonally by bacterial lipopolysaccharide (LPS) to secrete Ig and perform Ig class switch. In the presence of the T-cell lymphokine B-cell differentiation factor, the frequency of IgG1-secreting cells is drastically enhanced. We show here that IgG1-secreting B cells isolated from such cultures have undergone a similar DNA rearrangement of the switch regions (S mu, S gamma 1) of the Ig heavy chain constant region genes C mu and C gamma 1 on both active and inactive IgH loci. This result argues against a stochastic model of class switch recombination and suggests programmed class-specific switch recombination in the case of the switch to IgG1. In accord with this notion, cells expressing IgM but not IgG on the surface have not deleted or rearranged C mu or S gamma 1 on either chromosome.
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PMID:Class switch recombination is IgG1 specific on active and inactive IgH loci of IgG1-secreting B-cell blasts. 308 72

In the present study, the transient expression of the human immunoglobulin heavy chain gene (HIG1) was analyzed in a mouse pre-B-cell line, 70Z/3, after LPS stimulation. HIG1 gene and its recombinant plasmids were transfected by the calcium phosphate method into 70Z/3 cells and the cells were stimulated with lipopolysaccharide (LPS) 48 hr after DNA transfection. The amounts of human heavy chain gene products greatly increased in 70Z/3 cells after LPS stimulation, but the increment was diminished by deletion of the heavy chain gene enhancer element (MluI-HpaI fragment) in the J-C intron from the HIG1 gene. The gene, delta 3, which contained the 5' promoter region and the rearranged VDJ region of HIG1 but lacked the enhancer element, was weakly transcribed in 70Z/3 cells after LPS stimulation. Insertion of the enhancer element into the delta 3 gene greatly enhanced the transcription of the VDJ gene. The highest enhancement of the VH gene transcription rate was obtained when the 3' half of the enhancer element was ligated to the delta 3 gene. The present data suggest that the 3' half of the enhancer element of the heavy chain gene may play an important role in the enhanced production of immunoglobulin which is induced with LPS stimulation.
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PMID:The cis-acting regulatory elements of immunoglobulin heavy chain gene involved in enhanced immunoglobulin production after lipopolysaccharide (LPS) stimulation. 311 9

Splenic B lymphocytes were stimulated with lipopolysaccharide alone or in combination with phorbol-12,13-dibutyrate, a protein kinase C-activating phorbol ester. The effect of the treatment was analysed at the single cell level with in situ RNA/RNA hybridization. Hybridization with a kappa light chain probe revealed that the whole population had shifted towards a low, but significant, expression of immunoglobulin mRNA. Analysis at the population level was performed by DNA/RNA and RNA/RNA hybridization experiments. It was found that the steady-state levels of mRNA for kappa light chain, IgM heavy chain and J chain were reduced by phorbol ester treatment, while the steady-state level of mRNA for IgD heavy chain was increased. Steady-state levels of mRNA for Ia antigen and alpha-actin were marginally affected.
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PMID:Effects of phorbol esters on B-cell gene expression. 314 52


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