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Results for “antigen expression and secretion”

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At least 19 recordsLinked to original sources

PubMed1991

Effect of alpha-IFN on cytokine-induced antigen expression and secretion of TNF, LT and IgM in HCL.

In order to investigate the possible mechanisms for the effect of alpha-interferon (alpha-IFN) in hairy cell leukaemia (HCL), blood cells from 4 cases were treated in vitro with alpha-IFN, tumour necrosis factor (TNF) and interleukin 2 (IL-2). Changes in the antigen expression, immunoglobulin (Ig) secretion and the production of TNF and lymphotoxin (LT) were investigated. TNF induced expression of CD4 and CD71, increased the intensity of HLA-DR, CD25, CD11c and CD13 expression and decreased both the intensity and frequency of sIg and cIg positivity. alpha-IFN decreased CD25 expression, the tartrate-resistant acid phosphatase activity (TRAP), reduced the TNF-induced CD4 and CD71 expression and antagonized the TNF effect on the Ig expression. Spontaneous TNF or LT production could not be detected in culture supernatants. However, TNF was found to induce LT production, an effect which alpha-IFN antagonized and IL-2 augmented. The reduction of CD25, TNF-induced CD71 and TRAP caused by alpha-IFN seems to represent a deactivation of the activated state of hairy cells (HCs). The failure of alpha-IFN to induce Ig secretion or CD38 expression in HCs speaks against a differentiation induction effect. The LT secretion induced by TNF suggests that other cytokines than TNF might be involved in the proliferation of HCs and that alpha-IFN by blocking the production of LT and perhaps other cytokines causes a growth arrest in HCs.

Adult↗

PubMed1992

Functional heterogeneity of rat liver macrophages: interleukin-1 secretion and Ia antigen expression in contrast with phagocytic activity.

To clarify whether immunological heterogeneity exists among liver macrophages and whether this possible heterogeneity corresponds to varying degrees of phagocytic activity, we fractionated liver macrophages according to size via centrifugal elutriation and studied their ability to ingest latex beads, to express Ia antigen and to secrete interleukin-1 (IL-1) in vitro. Larger liver macrophages were found to be more active in ingesting latex beads than smaller ones (p less than 0.01), while smaller liver macrophages were more active in Ia antigen expression and evidenced greater fluorescence at cytofluorometric examination. In addition, smaller liver macrophages elaborated more IL-1 than the larger liver macrophages (p less than 0.05). These results indicate that liver macrophage heterogeneity is seen in at least two important macrophage functions: phagocytosis of large molecules, which provides an important scavenger function, and Ia antigen expression and IL-1 secretion, important components of the immune response.

Animals↗

PubMed1992

Cytological immunodetection of yeast glycoprotein secretion.

Expression of antigenic epitopes shared by secreted yeast glycoproteins was studied using specific immunological probes. Application of cytological and ultrastructural methods of immunodetection, employing monoclonal antibodies, permitted us to localize these glycoproteins in the cytoplasm, through the cell wall and at the yeast cell surface. Importance of glycosylation-secretion relationships were evaluated in the secretion process of these molecules. The cell wall crossing and the cell surface distribution of antigenic glycoproteins was described in immunoelectron microscopy and immunofluorescence. Some preferential secretion "ways" were suspected through the yeast cell wall leading to an heterogenous distribution of cell surface glycoproteins destined to be excreted into the medium. Antigenic variability of cell wall glycoproteins expression was discussed in relation with the glycoprotein secretion.

Antibodies, Monoclonal↗

PubMed1979

Clonal evolution of myeloma cells leads to quantitative changes in immunoglobulin secretion and surface antigen expression.

We report that a cloned population of tumor cells can rapidly produce variants that differ in their quantitative expression of surface proteins and in their rate of immunoglobulin secretion. A fresh clonal isolate of S107 myeloma cells possessing large amounts of surface IgA was continuously passaged in vitro for 2 years. During this period, fluorescence-activated cell sorter analysis indicated the development of subpopulations possessing decreased amounts of surface IgA. Cells from these variant subpopulations were isolated by first using the cell sorter to enrich for cells with decreased amounts of surface IgA and then cloning the selected population in soft agar. The 50 sublines that were isolated showed heritable differences in their levels of surface IgA and H-2 antigens and in their rates of myeloma protein secretion. Sublines having either large amounts, intermediate amounts, or absence of surface IgA also had corresponding large amounts, intermediate amounts, or absence of myeloma protein secretion. In contrast, a decrease or loss of surface Ig did not correlate with a decrease or loss of viral envelope glycoprotein gp71 and H-2 antigens. The variants did not resemble the phenotypes of less-differentiated normal lymphocyte populations of the B-cell lineage. The isolation and characterization of these variants allows us to explore the mechanisms and pathways of tumor cell differentiation as well as to study the regulation and function of cell surface proteins.

Animals↗

PubMed1990

Expression and secretion of preS containing hepatitis B surface antigen in vaccinia virus system.

The expression and secretion of preS containing hepatitis B surface antigen in vaccinia virus system was investigated. The human TK- 143 cells were infected with the recombinant vaccinia viruses vTMS-1 or vTLS-1. Cells infected with vTMS-1, which contains the preS2 + S gene, produced preS2 containing middle HBsAg proteins. Similarly, cells produced preS1 containing large HBsAg proteins upon infection with vTLS-1, which carries the preS1 + preS2 + S gene. The expression products could be secreted and form 22 nm particles. They reacted specifically with anti-preS1 and/or anti-preS2 monoclonal antibodies, and exhibited pHSA-receptor (for polymerized human serum albumin) activity. In addition, the major S components of hepatitis B surface antigen were also present in the products expressed by vTMS-1 and vTLS-1.

Cells, Cultured↗

PubMed1991

Multilineage antigen expression and possible autocrine secretion of an interleukin 1 by Ph1-positive leukemic cell line KOPM-28.

A newly established Ph1-positive cell line, KOPM-28 was analyzed for immunological phenotype and the release of biological substance. The surface marker analysis revealed myelomonocytoid antigens, erythroid antigens and megakaryocyte-platelet antigens. Also, the cells could be induced for hemoglobin synthesis by the addition of hemin. The conditioned medium of this cell line showed the presence of interleukin 1 (IL-1) activity but not interleukin 2. Exogenous IL-1 and the conditioned medium stimulated the DNA synthesis of the cells themselves. Consequently, the yield substance works on the growth of original cells as an autocrine fashion, and might act on other normal cells as a paracrine factor.

Antigens, Neoplasm↗

PubMed1992

Human glioblastoma cell line 86HG39 activates T cells in an antigen specific major histocompatibility complex class II-dependent manner.

The capacity of three different human glioblastoma cell lines to activate human T cells was analysed by measuring major histocompatibility complex (MHC) antigen expression, monokine secretion and lectin, mAb OKT3 and antigen-driven T cell proliferation. All glioblastoma cells tested were able to induce PHA and concanavalin A (ConA)-driven T cell proliferation in a dose-dependent fashion, while all failed to induce T cell activation with mAb OKT3. In addition, the glioblastoma cell line 86HG39 was able to induce tetanus toxoid and toxoplasma lysate antigen-specific T cell proliferation. The responding T cell lines originated from only one out of five different donors. This foreign antigen-specific T cell proliferation induced by 86HG39 cells could be inhibited with mAb L243 directed against HLA-DR molecules. The study of monokine secretion by 86HG39 cells showed a strong interleukin (IL)-6 secretion after lipopolysaccharide (LPS) treatment, whilst no IL-1 secretion was observed. Furthermore, only 86HG39 cells were positive for HLA-DR molecules, whereas interferon (IFN) gamma treatment of 87HG28 and 87HG31 cells was necessary for the induction of class II antigen expression. Thus, cell line 86HG39 shows many features of an antigen presenting cell and the interaction of these cells with MHC compatible human T cells might be a useful model to study cellular immune reactions within the central nervous system.

Animals↗

PubMed1990

Effects of gamma-interferon on DR antigen expression, growth, 3,5,3'-triiodothyronine secretion, iodide uptake, and cyclic adenosine 3',5'-monophosphate accumulation in cultured human thyroid cells.

We have examined, using the same system of human thyroid cells in culture, the effects of the cytokine human gamma-interferon (gamma IFN) on the expression of DR antigen, cell pro-liferation, cAMP accumulation, and the differentiated functions, iodide uptake and T3 secretion. gamma IFN elicited a dose- and time-dependent increase in DR expression, with a maximum effect on day 5 of culture. The cytokine, at the same concentrations and experimental conditions as those found to be effective in inducing DR antigen expression, caused on day 5 of culture a dose-dependent inhibition of [3H]thymidine incorporation, DNA content, cell count, as well as TSH-stimulated (but not basal) iodide uptake and T3 secretion. The gamma IFN suppressive influence on the differentiated functions was not merely due to a reduction in cell number, but was also apparent when results were expressed per micrograms DNA. Since the cytokine did not inhibit TSH- or forskolin-stimulated cAMP accumulation and showed a suppressive influence toward 8-bromo-cAMP- and forskolin-stimulated T3 secretion, its inhibitory effect seems to be exerted at a site located distal to cAMP formation. Although gamma IFN alone was devoid of any effect on cAMP accumulation, it enhanced forskolin-stimulated (as well as TSH-activated) cAMP in the presence of 3-isobutyl-1-methylxanthine, an inhibitor of cAMP degradation. Thus, it would seem that gamma IFN also exerts an influence on cAMP formation (rather than degradation) at a step subsequent to TSH binding to its receptor. The effects we observed seem specific to gamma IFN, since alpha IFN, although capable of inhibiting human thyrocyte multiplication, lacked any influence on DR antigen expression, cAMP accumulation, or T3 secretion by human thyroid cells. In what way, if any, is gamma IFN-induced DR antigen expression on human thyrocytes, an event believed to be critical in the pathophysiology of autoimmune thyroid disease, related to decreased thyroid function and growth is presently unknown.

Cell Count↗

PubMed1992

Identification and characterization of epitopes shared between the mycobacterial 65-kilodalton heat shock protein and the actively secreted antigen 85 complex: their in situ expression on the cell wall surface of Mycobacterium leprae.

Both mycobacterial hsp65 and the actively secreted antigen 85 complex of 30-kDa region proteins are considered to be major immune targets in mycobacterial diseases. In this study, by using a novel series of monoclonal antibodies (MAbs) directed to these antigens, we identified and partially characterized three unique epitopes (Rb2, Pe12, and A2h11) that are shared between mycobacterial hsp65 and the individual components of the antigen 85 complex. Dot blot assays with native purified proteins revealed that all three MAbs are strongly bound to hsp65 and antigens 85A (MPT44) and 85B (MPT59), while a weak reaction or no reaction was found with antigen 85C (MPT45). Immunoblotting showed that MAb Rb2 reacted strongly with both hsp65 and the antigen 85 complex proteins, whereas MAbs Pe12 and A2h11 reacted strongly with the former but weakly with the latter. Moreover, these MAbs did not react with other closely related MPT51 and MPT64 secreted proteins. Further characterization of these epitopes was performed by using recombinant fusion and truncated proteins of Mycobacterium bovis BCG hsp65 (MbaA) and the M. leprae 30- and 31-kDa antigen 85 complex fusion proteins. In hsp65, Rb2-Pe12- and A2h11-reactive epitopes were found to reside in the C-terminal region of amino acid residues 479 to 540 and 303 to 424, respectively. In the M. leprae 30- and 31-kDa antigen 85 complex, all three epitopes were located in an N-terminal region of amino acid residues 55 to 266, one of the known fibronectin-binding sites of the M. leprae antigen 85 complex. Comparison of these MAb-reactive amino acid sequence regions between mycobacterial hsp65 and the components of the antigen 85 complex revealed that these regions show certain amino acid sequence identities. Furthermore, by immunoperoxidase and immunogold ultracytochemistry, we demonstrated that Rb2-, Pe12-, and A2h11-reactive epitopes are expressed both on the cell wall surface and in the cytosol of M. leprae bacilli within the lesions of lepromatous leprosy patients and in M. leprae-infected armadillo liver tissue.

Amino Acid Sequence↗

PubMed1992

Immunity to B16 melanoma in mice immunized with IL-2-secreting allogeneic mouse fibroblasts expressing melanoma-associated antigens.

Co-presentation of weak tumour-associated antigens along with strongly immunogenic determinants leads to the development of an anti-tumour immune response in recipients syngeneic with the tumour. Tumour immunity develops in mice immunized with tumour cells modified by the introduction of cDNA for interleukin-2 (IL-2). Here, we report the anti-tumour response following immunization with an IL-2-secreting cell construct that expresses tumour-associated antigens, along with allogeneic major histocompatibility antigens. The construct was prepared by transfecting LM(TK-) mouse fibroblasts (H-2k) with genomic DNA from B16 melanoma cells syngeneic in C57BL/6J mice (H-2b). Transfectants expressing melanoma-associated antigens (MAA) were then infected with an expression-competent retroviral vector containing a cDNA specifying human IL-2. Cytotoxicity toward B16 cells was detected for as long as 5 months in both spleen and macrophage cell populations in C57BL/6J mice immunized with the IL-2-secreting cells. Mice immunized with non-IL-2-secreting, MAA-positive allogeneic cells developed melanoma immunity as well, but to a lesser extent. Immunity to 2 tumour-cell lines expressing the H-2d haplotype and to YAC-1 cells was detected in peritoneal macrophages, but not in spleen cells from C57BL/6J mice immunized with the cell construct, indicating that the response to B16 cells was only partially specific. C57BL/6J mice immunized with the IL-2-secreting cell construct survived significantly longer, following an injection of viable B16 cells, than mice in various control groups. The contribution of allogeneic antigens to the melanoma immunity was indicated by the failure of mice syngeneic with LM(TK-) cells to develop melanoma immunity following immunization with non-IL-2-secreting, MAA-positive cell constructs. The formation of IL-2 partially compensated for the lack of allogeneic antigens.

Animals↗

PubMed1990

Enhanced expression and secretion of an epithelial membrane antigen (MA5) in a human mucinous breast tumor line (BT549).

The mouse monoclonal antibody MA5, generated versus a membrane-enriched extract of breast cancer metastatic to liver, detects one or two high molecular weight species (greater than 200 kD) in breast tumor membranes, human milk fat globule membranes, and various breast tumor cell lines. From comparative studies of five breast carcinoma lines (BT20, BT549, MCF-7, T47D, and ZR75-1), as well as an epithelial line established from milk (HBL-100), we report the stimulation of expression of MA5-reactive antigen in a mucinous breast tumor cell line (BT549) through the use of a culture medium supplemented with charcoal-absorbed fetal calf serum, insulin, and hydrocortisone. Large amounts of aggregated MA5-reactive antigen are secreted into the culture medium and can be recovered from the media for further purification by centrifugation. These findings suggest that BT549 cells, grown in the special nutritive medium, may be useful in providing an ample source of epithelial membrane antigen (also termed polymorphic epithelial mucin) for standardization of clinical assay protocols, as well as provide a model system for studies of the regulation of expression for this class of antigens in breast carcinoma.

Adenocarcinoma, Mucinous↗

PubMed1992

Identification of a prenylation site in delta virus large antigen.

During replication, hepatitis delta virus (HDV) switches from production of small to large delta antigen. Both antigen isoforms have an HDV genome binding domain and are packaged into hepatitis B virus (HBV)-derived envelopes but differ at their carboxy termini. The large antigen was shown to contain a terminal CXXX box and undergo prenylation. The large, but not the small, antigen formed secreted particles when expressed singly with HBV surface antigen. Mutation of Cys211 in the CXXX box of the large antigen abolished both prenylation and particle formation, suggesting that this site is important for virion morphogenesis.

3T3 Cells↗

PubMed1992

New strategies for active immunotherapy with genetically engineered tumor cells.

While previous tumor vaccine strategies have shown intriguing results, clearcut efficacy has been difficult to establish in human trials. Recently, newer approaches have been developed in animal systems that modify tumor cells genetically so that they express new antigens or secrete certain cytokines. Engineering tumor cells to secrete cytokines in a paracrine fashion can induce powerful local cytokine effects without producing significant systemic toxicity. In addition to local inflammation, this approach can alter the presentation of tumor antigen or activation of tumor antigen-specific T lymphocytes, resulting in systemic antitumor immunity.

Genes, MHC Class II↗

PubMed1991

Bacterial expression and secretion of various single-chain Fv genes encoding proteins specific for a Salmonella serotype B O-antigen.

Active single-chain Fv molecules encoded by synthetic genes have been expressed and secreted to the periplasm of Escherichia coli using the ompA secretory signal. Four different constructs were developed to investigate the effects of peptide linker design and VL-VH orientation on expression, secretion, and binding to a Salmonella O-polysaccharide antigen. Peptide linker sequences derived from the elbow regions of the Fab molecule were used alone or in combination with the flexible (GGGGS)2 sequence. VL and VH domain order in the single chain molecules had a profound effect on the level of secretion but hardly influenced total expression levels, which were approximately 50 mg/liter, chiefly in the form of inclusion bodies. With VL in the NH2-terminal position, the amount of secreted product obtained was 2.4 mg/liter, but when VH occupied this position the yield was less than 5% of this value. Enzyme immunoassays of the four products showed domain order and linker sequence affected antigen binding by less than an order of magnitude. Attempts to express active Fv from dicistronic DNA were unsuccessful, but active Fv was obtained from single-chain Fv by enzymic cleavage at a site in the elbow linker peptide. The thermodynamic binding parameters of intact and cleaved single-chain Fvs determined by titration microcalorimetry were similar to those of bacterially produced Fab and mouse IgG.

Amino Acid Sequence↗

PubMed1991

Induction of plasmacytomas secreting antigen-specific monoclonal antibodies with a retrovirus expressing v-abl and c-myc.

ABL-MYC, a recombinant murine retrovirus that expresses v-abl and c-myc, rapidly induces transplantable mono- or oligoclonal plasmacytomas in BALB/c mice. To determine if the targets for transformation of this retrovirus are antigen-committed B lymphocytes and to explore this system as an alternative technique for producing antigen-specific monoclonal antibodies, plasmacytomas were induced in mice that had been immunized with two different types of immunogens, hen egg white lysozyme and sheep red blood cells. The majority of these plasmacytomas secreted immunogen-specific antibodies. Plasmacytomas induced in unimmunized mice did not react with hen egg white lysozyme or sheep red blood cells. The specific antibodies were comparable in concentration, specificity, and affinity to monoclonal antibodies obtained with conventional hybridoma technology, but, in addition to IgGs and IgMs, they included specific IgA antibodies, which are rare among splenic-derived hybridomas. Our results demonstrate that a principal target for ABL-MYC is an antigen-committed B lymphocyte. In addition this procedure provides an alternative method for the production of monoclonal antibodies, without a requirement for hetero-caryon formation by cell fusion techniques.

Animals↗

PubMed1992

Interferon-gamma regulation of C3 gene expression in human astroglioma cells.

In this report, we show that the human astroglioma cell line, D54-MG, constitutively expresses C3 mRNA and secretes antigenically detectable C3 protein. The cytokine interferon-gamma (IFN-gamma) enhances C3 mRNA and protein expression by D54-MG cells in a dose- and time-dependent manner. C3 mRNA from both D54-MG cells and primary human adult astrocytes has the same apparent size (5.1-5.2 kb) as C3 mRNA from hepatocyte and monocyte cell lines. Constitutive C3 mRNA levels in D54-MG cells and primary human astrocytes are comparable. Primary rat astrocytes also constitutively express C3 mRNA, which is enhanced upon exposure to IFN-gamma. These data are novel since expression of C3 in other cell types is refractory to IFN-gamma. In the central nervous system (CNS), endogenous complement production by astrocytes, and enhancement by the cytokine IFN-gamma, may contribute to the pathogenesis of inflammatory demyelinating diseases such as multiple sclerosis (MS).

Astrocytes↗

PubMed1992

Baculovirus recombinant expressing a secreted form of a transmembrane carcinoma-associated antigen.

GA733-2 is a monoclonal antibody-defined, 40-kDa glycoprotein antigen that is associated with carcinomas of various origins. Hydrophobicity analysis of the protein sequence predicted by complementary DNA (cDNA) has suggested that the GA733-2 antigen is a type I membrane protein. In this study, the polymerase chain reaction was used in a strategy to omit cDNA sequences for the transmembrane and cytoplasmic domains, thereby converting the extracellular domain into a secretory protein. Full-length and truncated cDNAs were cloned into the baculovirus transfer vector pVL1392 and introduced into Autographa californica nuclear polyhedrosis virus by homologous recombination. The full-length cDNA baculovirus recombinant directed the expression of a 40-kDa glycoprotein that was confined to infected Spodoptera frugiperda cells, whereas cells infected with the truncated cDNA baculovirus recombinant abundantly secreted a 31-kDa glycoprotein into the culture medium. Recombinant secretory antigen displayed an in vitro immunoreactivity to monoclonal antibody and an in vivo immunogenicity in mice that were similar to native antigen. The facile purification of mg quantities of carcinoma-associated antigen will enable an evaluation of its immunogenicity in cancer patients.

Animals↗

PubMed1990

Establishment of a foreign antigen secretion system in mycobacteria.

In order to develop recombinant Mycobacterium bovis BCG into a useful multivaccine vehicle, we established a foreign antigen secretion system in mycobacteria in which an extracellular alpha antigen of Mycobacterium kansasii was utilized as a carrier. By using this system, a B-cell epitope (Glu-12-Leu-Asp-Arg-Trp-Glu-Lys-Ile-19) of human immunodeficiency virus type 1 p17gag, which was identified by a fusion protein-based method, has been successfully obtained from BCG along with the alpha antigen. This is the first report of expression and secretion of a foreign viral antigen from BCG. It is possible that the system can become a universal vaccination vehicle applicable to protection against various infectious diseases.

Amino Acid Sequence↗