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

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

Mice were immunized against fluorescein isothiocyanate (FITC)-labelled human gamma globulin (HGG) in the absence or presence of different adjuvants. The immune response was assayed every other day with regard to both total Ig-secreting cells and FITC-specific plaque-forming cells (PFC). The adjuvants influenced the type of immune response induced to the same antigenic determinant. Thus, addition of Freund's complete (FCA) or incomplete (FIA) adjuvant preferentially led to the secretion of IgG1 PFC of an average high affinity. Most newly appearing IgG-secreting cells were also detected as FITC-specific PFC. The use of lipopolysaccharide (LPS) as an adjuvant resulted in the induction of both IgM and IgG, particularly of the IgG3 and IgG2b subclasses. However, these antibodies had relatively low affinity, and a large number of total IgG-secreting cells induced by LPS had no detectable FITC specificity. The FCA/FIA- and LPS-induced responses to FITC-HGG were additive when injected together, indicating that they act on distinct subpopulations of B lymphoid cells. The adjuvant response to LPS, but not the response to FCA/FIA, was totally absent in mice of the C3H/Hej strain, which are non-responders to the polyclonal activating properties of LPS. Finally, the response induced by FCA or FIA was T-cell-dependent and the LPS response T-cell-independent as assayed in nude mice.
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PMID:Adjuvants influence the immunoglobin subclass distribution of immune responses in vivo. 642 31

The effects of natural and recombinant human gamma-interferon (IFN-gamma) on mouse monoclonal antibody-dependent cellular cytotoxicity (ADCC) mediated by U937 human monocytic-like cells were examined. The efficiency of mouse monoclonal antibody of different isotypes in inducing ADCC was also compared. The number of receptors for the Fc portion of immunoglobulin G (IgG) (FcR) for mouse IgG2a and IgG3 on U937 cells, as detected by IgG antibody-sensitized erythrocyte rosette formation, was significantly enhanced by IFN-gamma. In contrast, FcR for mouse IgG1 and IgG2b were not detected even after IFN-gamma stimulation. U937 cell-mediated ADCC against sheep or ox red blood cell targets was minimal. However, after incubation with human purified IFN-gamma, U937 cells exhibited increased activity in IgG2a- and IgG3-dependent lysis, whereas their activity in IgG1- and IgG2b-dependent lysis was low. ADCC stimulated by IFN-gamma was inhibited by Protein A. When mouse peritoneal exudate cells were used, FcR for all IgG isotypes were easily detected, and all IgG isotypes mediated ADCC. Taken together, these results indicate that IFN-gamma induces U937 cell ADCC with mouse IgG2a and IgG3 partly through augmentation of FcR expression. Recombinant IFN-gamma showed the same effect as natural IFN-gamma. These effects of IFN-gamma were completely abrogated by anti-IFN-gamma serum but not by anti-IFN-alpha or normal rabbit serum. Addition of polymyxin B or lipopolysaccharide did not affect the activity of IFN-gamma.
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PMID:Induction of mouse IgG2a- and IgG3-dependent cellular cytotoxicity in human monocytic cells (U937) by immune interferon. 643 64

Two murine monoclonal antibodies of the IgG3 class have been isolated after immunization with Brucella abortus. An indirect immunofluorescence test was used to screen hybridoma supernatants and subsequently to determine the cross-reactivity of the monoclonal antibodies with other bacteria. One monoclonal antibody reacted with all the smooth Brucella biotypes tried and with Yersinia enterocolitica serogroup 0:9, though not with rough Br. ovis or with strains of Escherichia, Proteus, Salmonella, Pseudomonas, Francisella and Bordetella. The other monoclonal antibody displayed a high degree of specificity for brucellae carrying the A lipopolysaccharide-protein surface antigen. The implications for the diagnosis of brucellosis are discussed.
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PMID:A monoclonal antibody specific for the A antigen of Brucella spp. 643 72

To gain insight into how T cell-derived lymphokines induce the secretion of IgG in activated B cells, we performed a limiting dilution analysis, using murine splenic B cells incubated with lipopolysaccharide (LPS) and a T cell-derived B cell differentiating factor for IgG (BCDF gamma)-containing supernatant (SN). The results of this analysis indicate that such a SN induces a marked increase in the precursor frequency of IgG1-secreting cells and a modest increase in clone size. The precursors lack surface IgG and are committed to the differentiation pathway for IgG1 secretion after LPS activation, but before the addition of BCDF gamma-containing SN. The majority of IgG1-secreting clones arise independently from precursors of cells that secrete IgG3. Taken together, these results indicate that BCDF gamma directs differentiation of activated B cells to IgG1 secretion.
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PMID:Clonal analysis of B cells induced to secrete IgG by T cell-derived lymphokine(s). 643 16

The production of all immunoglobulin isotypes except IgD was studied in a large number of single lipopolysaccharide (LPS)-reactive B cell clones. The majority, but not all, of the IgM-producing clones were found to secrete one or more other isotypes. IgG3 and IgG2b were most frequently found while IgA secretion was extremely rare. Many clones produced all four IgG subclasses and the statistical analysis of the data indicates, with a high degree of significance, that single clonal precursors give rise to progenies producing multiple isotypes. By assuming that intraclonal diversification follows the C-gene order in chromosome 12, the absolute switch probabilities of normal, unprimed LPS-reactive B cells can be calculated. The multi-potentiality of C-gene expression was further analyzed at the single cell level: a sizeable fraction of all activated B cells express two different IgG isotypes in the membrane-bound form, indicating consecutive switch events. In contrast, the majority of IgE and IgA secreting cells appear to switch directly from IgM. These results might reflect the functional relevance of S-region homologies in the control of C-gene expression.
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PMID:Intraclonal diversification in immunoglobulin isotype secretion: an analysis of switch probabilities. 676 93

C3H/HeJ T cells which specifically recognize B cell-surface antigens of the related, major histocompatibility complex-compatible C3H/Tif strain, can be substantially enriched in vitro by long-term exposure (2--6 wk) of primed lymph node cells to the relevant cellular antigens. These enriched T cells contain functional helper cells as demonstrated by their capacity to induce large numbers of Ig-secreting plaque-forming cells (PFC) in cultures of antigenic B cells. The cooperative interaction results in activation of a large fraction of all splenic B cells, with consequent exponential growth and maturation to high rate secretion of IgM, IgG1, and IgG2, but not IgG3. The IgM PFC response includes antibody specificities to a number of different antigens and can be considered, therefore, as polyclonal. The T helper cell-dependent B-cell response is insensitive to inhibition by anti-delta antibodies, and in contrast with lipopolysaccharide-induced PFC responses, is only partially sensitive to the inhibitory effects of anti-mu antibodies. Finally, B-cell activation to growth and maturation by helper T cells strictly required direct T-cell recognition of antigens on the surface of responding B cells, leading us to the conclusions that if any soluble factors are generated in the collaborative process, they are either antigen specific or incompetent to initiate B-cell growth.
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PMID:Specific T helper cells that activate B cells polyclonally. In vitro enrichment and cooperative function. 676 81

hybridomas secreting anti-Thy-1 antibodies were produced by fusing cells of the mouse myeloma line P3-NSI/1-Ag4-1 (NS-1) with spleen cells from AKR/J mice immunized with C3H/Di thymus cells and by subsequent growth in tissue culture and selection of the hybrid cells. Two permanent hybridomas, 1B5 and 1aG4/C5, secreting antibodies of IgG3 subclass were isolated by repeated cloning of cells by dilution and in soft agar. Growth of the hybrid cell colonies depended on the presence of feeder cells; spleen cells at 1-2 x 10(6)/ml were most effective, then thymus cells at 1-4 x 10(6)/ml and peritoneal cells at a concentration 1-2 orders of magnitude lower. The two hybridomas were grown in vitro or vivo and their products were further analysed. In tissue culture in serum-free medium under the optimum conditions the supernatant from hybridoma 1B5 contained 0.07 mg/ml of antibodies and that from hybridoma IaG4/C5 had 0.26 mg/ml of antibodies, whereas ascites 1B5 contained 3.6 mg/ml and ascites 1aG4/C5 4.4 mg/ml of antibodies. A very low electrophoretic mobility of both antibodies facilitated their isolation. The specificity of the antibodies was tested in the cytotoxicity assay in the presence of complement and by the binding of isotopically labelled antibodies to thymus cells from A/Ph mice and other Thy-1.2+ strains and A.Thy-1.1 and AKR/J mie. Antibodies of clone 1aG4/C5 were specific for Thy-1.2+ cells, whereas antibodies of clone 1B5 at higher concentrations also reacted with Thy-1.1+ cells from the thymus and lymph nodes. Both antibodies killed more than 95% thymus cells and 60-70% lymph node cells in the cytotoxicity assay. The specificity of antibodies for T lymphocytes was confirmed in the functional test in which the antibodies eliminated the response of spleen cells to Concanavalin A but did not affect the response to lipopolysaccharide in the presence of complement.
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PMID:Establishment and characterization of permanent murine hybridomas secreting monoclonal anti-thy-1 antibodies. 678 39

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

A cell wall extract from the gram-positive bacterium Actinomyces viscosus contains the mitogen AVIS, a potent polyclonal B-cell activator for murine B lymphocytes. Cultures of splenocytes from heterozygous nude mice in the presence of an optimal concentration of AVIS responded by a deoxyribonucleic acid synthesis response, and proliferaction reached maximal levels after 3 to 4 days. There was no requirement for T cells in the deoxyribonucleic acid synthesis, proliferactive, immunoglobulin M (IgM), or IgG responses. Significant numbers of IgM-producing cells were present as early as day 2 of culture, whereas later in the culture periods (days 3 to 6) IgG-producing plasmablasts and plasma cell were observed. In cultures of splenocytes from nude mice stimulated with AVIS for 4 to 5 days, 20 to 25% of the recoverable cells synthesized IgM, and 10% contained only IgG2 or IgG3; 5 to 8% of the cells stained for both IgM and IgG2 or both IgM and IgG3. Fine-structure analysis of AVIS-stimulated splenocytes from heterozygous nude mice after 3 days of culture demonstrated that 20 to 25% of the cells were activated to various degrees. Of most importance, all of the activated cells had the characteristic of B lymphoblasts, plasmablasts, or plasma cells. This is the first demonstration of a polyclonal B-cell activator other than lipopolysaccharide which induces IgG3 synthesis. We suggest that AVIS may be a useful probe for the exploration of the functional activities of subpopulations of B cells.
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PMID:In vitro expression of immunoglobulin M and G subclasses by murine B lymphocytes in response to a polyclonal activator from Actinomyces. 696 54


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