Biomedical subjects

S Dagan

Publications and source records attributed to S Dagan.

14 recordsLinked to original sources

PubMed1992

High-level expression and production of recombinant human interleukin-6 analogs.

We have constructed and analyzed different mutant forms of interleukin-6 (IL-6) expressed in Escherichia coli that can be divided into two groups. The first group contains four full-length IL-6 molecules that differ in the presence of cysteine residues involved in disulfide bridges. The second group contains 22 N-terminal amino acid deletions in addition to the differences in the cysteine residues. The different IL-6 muteins were extracted and their expression levels and solubility were compared. We found that the production levels of IL-6 can be dramatically improved by deleting the first 22 N-terminal amino acids of the molecule. We have also found that the production of IL-6 containing the four cysteine residues is lower than the production of the mutant molecules that lack one or both pairs of cysteines. The yield of soluble and properly refolded IL-6 was the highest when the disulfide bond between the cysteines at positions 74 and 84 was present in the mutein form, which also lacked the 22 N-terminal amino acids.

Amino Acid Sequence↗

PubMed1991

Isolation of a monoclonal antibody to the TrpE protein and its use for the purification of recombinant fusion proteins.

The trpE (or anthranilate synthetase) gene product has been used extensively as a fusion protein for the expression of a myriad of biologically active proteins. A trpE construct can be produced in high yield, is relatively resistant to proteolysis, and separates from the bulk of E. coli proteins because of its insolubility. We have isolated and characterized a monoclonal antibody against the TrpE protein for use as a detection and immunoaffinity reagent. The MAb, TRP 7.4, is highly specific for the TrpE protein and has a relative affinity of 1.0 ng. The antibody can also be used to detect TrpE constructs on Western blots. In addition, TRP 7.4 has been used to purify a TrpE-IL-6 fusion protein. These studies show the utility of this MAb as a tool for both research and protein purification.

Animals↗

PubMed1991

Glyco-tuftsin derivatives modulate interleukin-1 and tumor necrosis factor production.

Six Thr1 (O-glyco)-derivatives of the "phagocytosis stimulating peptide" tuftsin, H-Thr-Lys-Pro-Arg-OH and the N-glycosylated undecapeptide H-Thr-Lys-Pro-Arg-Glu-Gln-Gln-Tyr-Asn(beta-D-GlcNAc)-Ser-Thr-OH, which correspond to the "tuftsin-region" at the Fc-domain of immunoglobulin G (amino acid residues 289-299), were evaluated in comparison with tuftsin and rigin, H-Gly-Gln-Pro-Arg-OH, for their capacity to evoke the release of interleukin-1 and tumor necrosis factor from mouse peritoneal macrophages and from human monocytes. Several glycosylated tuftsin derivatives were found to modulate, in a rather dose-dependent manner, the release of the two cytokines from both cell types.

Amino Acid Sequence↗

PubMed1990

Further characterization of prolymphocytic leukemia cells as a tumor of activated B cells.

Peripheral blood mononuclear cells from 24 patients with prolymphocytic leukemia (PLL) were isolated using a Ficoll-Hypaque gradient and stained by indirect immunofluorescence using a wide panel of monoclonal antibodies against B cell restricted and associated antigens, including HLA DR (Ia), CD19, CD21 (C3dR) surface membrane immunoglobulin (Slg), CD10 (CALLA), C3b, B5, CD25 (TAC), PCA1, T9, and T10. The cells were also tested for the FMC7, defined previously on PLL cells and the RAB1, a newly described hairy cell leukemia antigen. Thirteen out of the 24 samples expressed with variable intensity all the above antigens. While Ia, CD19, CD20, FMC7, and RAB1 were strongly or moderately expressed in all, the complement receptors (CD21 and C3b) were only weakly expressed in 12 cases; and the activation antigens B5, TAC, T9, T10, and PCA1 were found with variable intensity in two-thirds of the cases. In 50% of the cases tested, the CD5 antigen (usually strongly expressed on B CLL cells) was weakly to moderately expressed. These findings (absence or weak expression of complement receptors with variable expression of activation antigens) suggest that the PLL cells are activated B cells. When stimulated in vitro by anti-mu and TPA, (phorbol ester) tumor cells showed a decrease in CD21 and Slg and a stronger expression of CD25, T9, T10, and PCA1, with evidence of Ig secretion in four out of the seven cases studied. This confirms that the PLL cells arrested at an advanced stage of differentiation progressed narrowly to more differentiated cells. In view of our findings, we believe that the term prolymphocytic leukemia is inaccurate to define the stage of cell differentiation, and we suggest calling the disease preplasmacytic leukemia.

Antibodies, Monoclonal↗

PubMed1990

Polytuftsin: a potential precursor for slow release of the phagocytosis stimulating peptide tuftsin.

1. Polytuftsin (Thr-Lys-Pro-Arg)n, was synthesized through polycondensation of an amino-free and carboxyl-activated derivative of tuftsin, H2N-Thr-Lys(Z)-Pro-Arg(Tos)-OSu, following suitable deprotection and fractionation steps. 2. Digestion of polytuftsin by trypsin, as well as by normal human serum, at 37 degrees C, yielded free tuftsin. 3. Polytuftsin affected the decreased formation of lung-metastasis, in B16 melanoma treated mice and prolonged the survival of animals more efficiently than tuftsin. 4. Tuftsin was found to be totally degraded by serum enzymes within approximately 60 min at 37 degrees C.

Amino Acid Sequence↗

PubMed1989

Immunogenic capacity of macrophage hybridomas.

Two clones, E2-7.7 and E2-10.50, derived from two macrophage(M phi)hybridomas, E2-7 and E2-10, have been studied. The first clone, E2-7.7, is Ia+ and Fc receptor (FcR) negative and manifests a strong antigen-presenting capacity. When we pulsed its cells in vitro with keyhole limpet hemocyanin (KLH) antigen and injected them into syngeneic animals, we found that as small a dose as 10(3) cells initiated an immune response in vivo. On the other hand, antigen-pulsed cells of the E2-10.50 clone, which are Ia- and FcR+, were almost incapable of triggering immunity, even when injected at a dose of 10(5) cells. Thus, the two clones differ in their immunogenic capacity (both cellular and humoral immunity). In experiments aimed at testing the stimulation in vitro of primed lymph node (LN) cells by antigen-pulsed cells of these two hybridoma clones, we observed that E2-7.7 stimulated the unfractionated population of LN cells and the LN-derived population of T cells. The E2-10.50 cells stimulated only the unfractionated population of LN cells, but not the T cell population. Subsequent tests indicated that the E2-10.50 cells require an intermediate Ia+ accessory cell to present the antigen to the T lymphocytes. Analyzing the molecular structure of the M phi hybridomas, we discovered that major histocompatibility complex (MHC) genes of the myeloma haplotype (H-2d), and of the splenic M phi used for fusion (H-2k), which were not expressed in the parental myeloma or in the E2-10.50, were expressed in the E2-7.7. Thus, somatic cell fusion of M phi resulted in the activation of suppressed genes of the myeloma partner. It appears that these antigens participate in controlling the immunogenic properties of the E2-7.7 clone. Testing the effects of interferons on the M phi hybridomas, we observed that interferon-gamma activated, at both the mRNA and the cell surface-antigen levels, the expression of H-2Dk, H-2Kd and H-2Dd in the E2-10.50 cells, but not in the E2-7.7. Consequently, interferon-gamma augmented significantly antigen presentation by E2-10.50 but not by E2-7.7 cells. These two hybridoma clones might represent two distinct subsets of normal M phi, manifesting two different sets of functional properties.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1989

Tuftsin stimulates IL-1 production by human mononuclear cells, human spleen cells and mouse spleen cells in vitro.

Human peripheral adherent cells from splenectomized subjects, human spleen cells and mouse spleen cells were tested for IL-1 production in vitro in presence or absence of synthetic tuftsin (Thr-Lys-Pro-Arg). Application of synthetic tuftsin to peripheral blood adherent cells from normal donors as well as from splenectomized subjects induces IL-1 production. In splenectomized subjects the extent of induction was more evident than in controls. In human splenic cells tuftsin stimulates IL-1 production without KLH or LPS. In mouse spleen cells tuftsin alone did not stimulate the IL-1 secretion. However, addition of tuftsin to mouse spleen cells incubated with KLH augmented significantly the IL-1 secretion. As removal of the spleen leads to tuftsin deficiency, our present findings may perhaps explain the fulminant nature of the postplenectomy sepsis and some immune disturbances described in the postplenectomy state.

Animals↗

PubMed1988

Antigen-tuftsin conjugate signals interleukin-1 synthesis and secretion.

The immunoglobulin heavy chain derived tetrapeptide, tuftsin (Thr-Lys-Pro-Arg), known for its phagocytosis-stimulating activity, was found to augment the antigen-presenting capacity of macrophages in culture, when applied simultaneously with antigen. Injection of antigens or antigens admixed with tuftsin had no immunogenic effect in vivo. On the other hand, antigen-tuftsin covalent conjugates, injected in aqueous solution intramuscularly or intravenously, significantly augmented antibody production. Studying the mechanism underlying these immunogenic effects, we demonstrate that tuftsin, when applied to macrophages together with, or conjugated to, antigens, signals de novo synthesis of mRNA encoding for interleukin-1 (IL-1), and induces secretion of IL-1 from the cells. We suggest that triggering the immunogenic processes by tuftsin conjugates is a consequence of up-regulation of IL-1 synthesis and secretion.

Animals↗

PubMed1987

Synthesis of modified tuftsins containing monosaccharides or monosaccharide derivatives.

Synthesis of some modified tuftsins is described in which a monosaccharide or a monosaccharide derivative was incorporated in the molecule. Acylation of H-Thr-Lys(Z)-Pro-Arg(NO2)-OBzl with D(+)-gluco-1,5-lactone followed by catalytic hydrogenation gave N alpha-gluconyl-tuftsin. Glycosylation of the carboxyl function of the C-terminal arginine has been achieved by reacting, through the mixed anhydride procedure, Boc-Thr-Lys(Z)-Pro-OH with 2-deoxy-2-(NG-nitroargininamido)-D-glucopyranose followed by catalytic hydrogenation and trifluoroacetic acid treatment. O-Glucosyl-tuftsin has been prepared by reacting o-nitrophenyl N-benzyloxycarbonyl-O-[(alpha + beta) 2,3,4,6-tetra-O-benzyl-D-glucopyranosyl]-threoninate with H-Lys(Z)-Pro-Arg(NO2)-OBzl in the presence of 1-hydroxybenzotriazole. Flash chromatography on silica gel allowed a partial separation of the diastereoisomers, one of which has been isolated in a reasonable yield. The single diastereoisomer and the alpha + beta anomeric mixture were separately deblocked by catalytic hydrogenation and purified by RP-HPLC.

Carbohydrates↗

PubMed1987

Synthesis and biological activity of tuftsin and rigin derivatives containing monosaccharides or monosaccharide derivatives.

Synthesis of some modified rigins is described in which either D-gluconic acid or 2-amino-2-deoxy-beta-D-glucopyranose have been linked to the parent molecule through amide bonds involving the alpha-amino function, alpha-carboxyl function or the gamma-amide function of glutamine in position 2. Glu2-rigin and D-gluconyl-Glu2-rigin have also been synthesized. Binding and phagocytosis assays have been carried out on the rigin derivatives and on some glycosylated tuftsin derivatives as well. Of all the tested peptides only rigin enhanced the phagocytic capacity of mouse peritoneal macrophages to the same extent as tuftsin. The peptides H-Thr-Lys-Pro-Arg-NH-Glc and N alpha-gluconyl-Gly-Glu-Pro-Arg-OH slightly enhanced phagocytosis. H-Thr[(alpha + beta)-O-glucosyl]-Lys-Pro-Arg-OH was found to displace 3H-tuftsin even better than tuftsin but lacked the ability to stimulate phagocytosis.

Animals↗

PubMed1987

Tuftsin and tuftsin conjugates potentiate immunogenic processes: effects and possible mechanisms.

The immunoglobulin heavy chain associated tetrapeptide, tuftsin (Thr-Lys-Pro-Arg), known for its phagocytosis-stimulating activity was found to augment the antigen presenting capacity of macrophages in culture when applied simultaneously with the antigen. To study the immunogenic effect of tuftsin in vivo the peptide was coupled covalently to keyhole limpet hemocyanin (KLH) and bovine serum albumin (BSA) antigens to form stable entities. Tuftsin-antigen conjugates were found to be very potent immunogens as tested by their capacity to increase antigen presentation in culture in primary and secondary responses. Thus, monolayers of macrophages pulsed in vitro with KLH-tuftsin conjugates exerted a stronger immunogenic effect than KLH alone. BSA, which by itself was not immunogenic, when applied to macrophages as tuftsin conjugate evoked a high lymphoproliferative immune response. In vivo, BSA conjugated to tuftsin, when injected in aqueous solutions, augmented significantly antibody production, whereas administration of BSA alone or BSA admixed with tuftsin had no immunogenic effect. Studies conducted to elucidate the mechanisms underlying the activation of the immunogenic function of macrophages by the peptide revealed that treatment of cells with antigen and tuftsin increases secretion of interleukin-1 and expression of cell surface Ia encoded antigens. The effect of tuftsin on increasing the immunogenic capacity of antigens may at least partly be attributed to these effects.

Adjuvants, Immunologic↗

PubMed1986

[Tuftsin].

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Humans↗

PubMed1986

Tuftsin analogues: synthesis, structure-function relationships, and implications for specificity of tuftsin's bioactivity.

Thirteen analogues of the natural macrophage activator peptide tuftsin, ten of which are novel, were synthesized with the aim of exploring the relation between their biological potency and their capacity to attach specifically to cellular tuftsin's receptors. The analogues representing modifications and chain extensions at various parts of the parent tuftsin molecule can be classified as N-terminal analogues, C-terminal analogues, "within-chain" derivatives, or dimers of tuftsin and retrotuftsin. The various synthetic routes employed to prepare the analogues are described. A direct correlation was found between the ability of analogues to inhibit [3H-Arg4]tuftsin specific binding to mice peritoneal macrophages and their capacity to enhance phagocytosis or to inhibit tuftsin-mediated phagocytosis by the cells and to potentiate the cell's immune response.

Animals↗

PubMed1985

Non-immune interaction of erythrophilic IgG fractions with human red blood cells.

Immunoglobulin G was separated on cellulose phosphate column to afford four distinct protein fractions (CP-I, II, III and IV). 125I-labeled fractions CP-III and CP-IV were found to be capable of binding specifically to normal human erythrocytes. The effect of the four fractions on osmotic resistance of red blood cells (RBC) was studied. RBC were obtained from eight patients with hereditary spherocytosis (HS), from a single parent of two non-related patients, and from five normal donors. RBC fragility of normal and one parent were unaffected by any of the immunoglobulin fractions. In contrast, a small but significant decrease in osmotic resistance was observed when RBC from HS patients and the second parent were incubated with protein fractions CP-III and CP-IV.

Adult↗