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S Hammarström

Publications and source records attributed to S Hammarström.

At least 91 records · Page 5Linked to original sources
PubMed1988

In vivo formation of omega-oxidized metabolites of leukotriene C4 in the rat.

[3H8]Leukotriene C4 was administered to germfree rats and to conventional rats having a bile duct cannula. Several radioactive metabolites were isolated. Two polar biliary metabolites from conventional rats were identified as N-acetyl-omega-carboxy-leukotriene E4 and N-acetyl-omega-hydroxy-leukotriene E4. A polar fecal metabolite from germfree rats was found to be N-acetyl-omega-carboxy-leukotriene E4. Chemical identities were established using UV spectroscopy and cochromatographies with authentic compounds in several HPLC systems. The fecal metabolite was further characterized by reductive desulfurization followed by gas-liquid-radiochromatography. The yield of the two biliary metabolites was 5% of the administered tritium after three hours and the yield of fecal N-acetyl-omega-carboxy-leukotriene E4 was 3.5% after three days.

Animals↗
PubMed1988

Characterization of human CD4+ T-cell clones that secrete helper factor(s) for B-cell proliferation and maturation.

Human peripheral blood lymphocytes (PBL) were activated with K46M, a m mitogenic monoclonal antibody against La-reactive T lymphocyte surface structures. The cultures were expanded in the presence of interleukin 2 (IL-2). After 1 month of culture, the activated T cells were cloned by limiting dilution at 0.5 cells/well. Five clones with the CD3+CD4+ phenotype and one clone with the CD3+CD8+ phenotype were obtained. The CD3+CD8+ clone (K99) displayed a strong major histocompatibility complex (MHC)-unrestricted cytolytic activity against MOLT-4 and a weaker reactivity against the bladder tumour cell lines T24 and RT4. The natural killer (NK)-susceptible K562 cells were not lysed. Two of the CD3+CD4+ clones (K91 and K914) showed a helper activity in pokeweed mitogen (PWM)-induced IgG production by B cells. These cells differed in the expression of CD45R and CDw29 antigens, as defined by the monoclonal antibodies 2H4 or D10D11 and 4B4. When stimulated with PWM for 48 or 72 h, clone K91 and an additional CD4-positive clone (K913) secreted a factor into the supernatants which helped B cells to produce IgG. The K913 supernatant also induced some IgM production. The supernatant obtained after similar stimulation of K914 cells was inactive. None of these supernatants induced B cells to proliferate when tested together with phorbol myristate acetate (PMA). However, when K91 and K914 cells were activated with phytohaemagglutinin (PHA) for 48 or 72 h, the supernatant from K91 was strongly helpful in B-cell proliferation, whereas the supernatant from K914 cultures was only moderately active. In conclusion, we have established human T helper clones that release different factors supporting either B-cell proliferation or maturation when stimulated with PWM or PHA.

Antigens, CD↗
PubMed1988

Monoclonal antibodies against leucoagglutinin-reactive human T-lymphocyte surface components. I. Characterization of cellular binding sites.

The binding specificities of three biologically active anti-lymphocyte monoclonal antibodies (MoAb) (K46M, K3G, and 3-19-2) produced against human T-cell surface components reactive with the mitogenic lectin leucoagglutinin from Phaseolus vulgaris (La) were analysed. K46M is a strong T-cell mitogen, while K3G and 3-19-2 inhibited cell-mediated cytotoxicity. Resting peripheral blood lymphocytes (PBL) contained 4-16% K46M+ cells, 8-35% K3G+ cells, and less than 0.3-4% 3-19-2+ cells. After stimulation with T-cell mitogens the proportion of K46M+ and 3-19-2+ cells increased markedly (mean 59 and 30% positive cells, respectively), while the increase in K3G+ cells was less prominent (38%). K46M-reactive structures were expressed on mature T cells and probably also on B cells. K3G reacted with B and T cells while 3-19-2 showed a broader specificity reacting also with erythrocytes. All three MoAb reacted with lipid extracts of resting and activated PBL as well as with purified neutral glycolipids of lymphoid origin. In addition 3-19-2 reacted with lipid extracts of erythrocytes. K46M immuno-precipitated four surface peptides from lectin-stimulated PBL. Their apparent molecular weights were 53,000, 42,000, and 16,000 (doublet). The 53,000 and 42,000 MW peptides were identified as the alpha and beta chains of the T-cell antigen receptor. The identity of the 16,000 MW peptides is presently unknown. K3G and 3-19-2 did not specifically precipitate any lymphocyte surface peptide.

Animals↗
PubMed1988

Monoclonal antibodies against leucoagglutinin-reactive human T-lymphocyte surface components. II. Studies on the mechanism of K46M-induced activation and determination of the frequency of responding cells.

A monoclonal antibody, K46M (IgM kappa), obtained after immunization with leucoagglutinin (La)-reactive T-cell surface components, stimulated human lymphocytes to proliferate. It induced maximal proliferation at greater than 20 micrograms IgM/ml after 3-4 days of culture. Cells stimulated by K46M produced interleukin 2 (IL-2) and gamma interferon (IFN-gamma) and expressed receptors for IL-2 and transferrin. The majority of the activated cells were phenotypically T cells as defined by monoclonal antibodies against CD3 and CD2, and an increase in the K46M-positive cells was also observed during the activation period. K46M-activated cells display major histocompatibility complex (MHC)-unrestricted cytotoxicity against several cultured target cells. The frequencies of the cytotoxic and of the proliferative precursor cells were determined using a limiting dilution assay. K46M seems to activate a larger fraction of cytotoxic precursor cells against Molt 4 than against K562, but the statistical significance of these observations requires further exploration. Both K46M or La activated 40% of PBL to proliferate, whereas 70% of PBL were induced by OKT3. However, the frequency of K46M-activated cells was 40% only when the lymphocytes were plated at low cell densities, i.e. less than 0.5 cells per well. At higher densities an inhibition of proliferation was seen that resulted in a biphasic response curve, indicating that the activation of PBL by K46M was not a single hit event. This was not found with either La or OKT3. Whether K46M, in contrast to OKT3 and La, activates a subpopulation with suppressor activity remains to be established.

Animals↗
PubMed1988

Studies on the role of lymphocyte function-associated antigen 1 (LFA-1) in T cell activation.

The effect of polyclonal (anti alpha and beta chain) and monoclonal (anti alpha-chain) antibodies against lymphocyte function-associated antigen 1 (LFA-1) on T cell activation was studied. When added at the beginning of activation but not after 24 h or later the antibodies as well as the F(ab')2 or Fab fragments of polyclonal antibodies inhibited concanavalin A (Con A)-induced proliferation, interleukin 2 (IL-2) production, and the expression of receptors for IL-2 and transferrin. The inhibitory effect reached a maximum at the same time as optimal proliferation (72 h). Inhibition of proliferation lasted for 5 days or longer, although IL-2 production was only inhibited during the first 48 h of culture. Receptors for IL-2 and transferrin were re-expressed to the original level after 3 days of activation. Addition of external IL-2 at the beginning of the anti-LFA-1 containing culture prevented the inhibition of IL-2 receptor expression, while inhibition of transferrin receptor expression was unaffected, supporting the conclusion that the expression of these two receptors is regulated by partially independent signals. The polyclonal and monoclonal anti-LFA-1 antibodies also inhibited phorbol ester (PMA)-dependent OKT3 activation of highly purified T cells. The results suggest that the LFA-1 antibodies block an early step in the reactions necessary for IL-2 production, and that the LFA-1 molecule participates not only in T cell-accessory cell interaction but also in T-T interaction during the early phases of the activation process.

Antibodies, Monoclonal↗
PubMed1988

Synergistic enhancement of mitogen responses of human lymphocytes by inhibitors of cyclo-oxygenase and lipoxygenase.

Previously we reported that inhibitors of the enzyme cyclo-oxygenase, which reduce biosynthesis of prostaglandins, may enhance mitogenic responses of human blood lymphoid cells, whereas only marginal effects were observed with 5,8,11-eicosatriynoic acid (ETI), which inhibits 12-lipoxygenase and leukotriene biosynthesis. However, sharply enhanced mitogen responses were observed when lymphoid cells were cultured with both a cyclo-oxygenase inhibitor and ETI, suggesting a synergy between the two drugs. To test whether this is a more general phenomenon occurring between inhibitors of cyclo-oxygenase and lipoxygenase, we have now extended these studies to include the following lipoxygenase inhibitors: cirsiliol; esculetin; 5,8,11,14-eicosatetraynoic acid, and nordihydroguaiaretic acid. The results have shown that any of these drugs combined with a cyclo-oxygenase inhibitor may enhance mitogen responses more than one would expect by summing the effects of the inhibitors tested separately. We conclude that inhibitors of cyclo-oxygenase and lipoxygenase may synergistically enhance mitogen responses of lymphoid cells.

Arachidonate Lipoxygenases↗
PubMed1988

Modulation of lymphocyte and monocyte responses in vitro by 9-deoxy-delta 9-prostaglandin D2 and 9-deoxy-delta 9-delta 12-prostaglandin D2.

The effects of 9-deoxy-delta 9-prostaglandin D2 (PGJ2) and 9-deoxy-delta 9-delta 12-prostaglandin D2 (delta 12PGJ2), which are metabolites of PGD2, on lymphocyte and monocyte reactions were studied in vitro. Expression of various phenotypic markers of lymphocyte subsets, as detected by monoclonal antibodies, was not affected by overnight incubation in 3 x 10(-5) M PGJ2. Phytohemagglutinin stimulation and natural killer activity of lymphocytes was reduced by PGJ2 and delta 12 PGJ2. Monocyte reactivity to 12-o-tetradecanoylphorbol-13-acetate, as assessed by chemiluminescence, was stimulated by preincubation of the cells for 1 h in 3 x 10(-5) M PGJ2 or delta 12 PGJ2. Such an augmentation was not exerted by PGD2.

Adjuvants, Immunologic↗
PubMed1987

Enzymatic conversion of leukotriene B4 to 6-trans-leukotriene B4 by rat kidney homogenates.

A novel isomerase reaction leading to conversion of leukotriene B4 to its 6-trans isomer was detected in rat kidney homogenates. The structure of the metabolite was determined by high performance liquid chromatography, ultraviolet spectrometry and gas-liquid chromatography-mass spectrometry. A recent report has shown that 6-trans-leukotriene B4 is transformed to a dihydro metabolite (6,7- or 10,11-dihydro 6-trans-leukotriene B4) and further omega-hydroxylated [Powell, W.S. (1986) Biochem, Biophys. Res. Commun. 136, 707-712]. The leukotriene B4 6-isomerase reaction reported here may therefore provide the first step in a novel pathway of biological degradation of leukotriene B4.

Animals↗
PubMed1987

Products, kinetics, and substrate specificity of homogeneous thromboxane synthase from human platelets: development of a novel enzyme assay.

Homogeneous thromboxane synthase from human platelets converted prostaglandin H2 (PGH2) to thromboxane A2 (measured as thromboxane B2, TxB2), 12(L)-hydroxy-5,8,10-heptadecatrienoic acid (HHT), and malondialdehyde (MDA) in equimolar amounts under a variety of experimental conditions. PGG2 was transformed to MDA and corresponding 15- and 12-hydroperoxy products. PGH1 was enzymatically transformed into 12(L)-hydroxy-8,10-heptadecadienoic acid (HHD) and PGH3 into TxB3 and 12(L)-hydroxy-5,8,10,14-heptadecatetraenoic acid (delta 14-HHT) as earlier reported for solubilized and partially purified thromboxane synthase preparations. The ratio of thromboxane to C17 hydroxy fatty acid formation was 1:1 with PGG2, PGH2, and PGH3 as substrates. These results confirm and extend earlier observations with partially purified enzyme that the three products are formed in a common enzymatic pathway (Diczfalusy, U., Falardeau, P., and Hammarström, S. (1977) FEBS Lett. 84, 271-274). A convenient spectrophotometric assay for thromboxane synthase activity measuring the ultraviolet light absorption of the C17 hydroxy acid formed (e.g., HHT) was developed. The validity of the assay was determined employing specific inhibitors for thromboxane synthase. The substrate specificity of thromboxane synthase was determined using this assay. PGG2 and PGH3 showed Vmax and KM values similar to those of PGH2. The KM value of PGH1 was also identical to that of PGH2 but the Vmax value PGH1 was more than twice as high as that of PGH2.

Blood Platelets↗
PubMed1987

Determination of intrinsic affinity constants of monoclonal antibodies against carcinoembryonic antigen.

A 2-phase method is described for the determination of the intrinsic affinity constants (K-values) for the interaction between monoclonal antibodies (MAbs) against carcinoembryonic antigen (CEA) and CEA. The Mabs were coupled covalently to CNBr-activated paper discs. MAb coupled discs and a 2-fold dilution series of 125I-CEA were incubated at 20 degrees C until equilibrium was reached. Nonlinear curve-fitting was used for estimation of K-values and different calculation models were thereby tested. The K-values for 12 different anti-CEA MAbs were determined to be 0.3-52 X 10(6) M-1, which is 1-2 orders of magnitude lower than the values obtained in a previous study with some of these MAbs using the ammonium sulphate method to separate free from bound antigen. The K-values obtained by the paper disc method are probably better estimates of the intrinsic association constant than those obtained previously. There are two main reasons for this: (1) free and bound antigen are separated from each other under physiological conditions and (2) the opportunity for multipoint interaction between MAb and CEA is minimized when the MAb is coupled to a rigid carrier substance. Thus, even when the MAb reacts with greater than or equal to 2 epitopes in CEA, as seems to be the case with several of our anti-CEA MAbs, the intrinsic K-value should be obtained. The fundamental validity of 2-phase assays, sometimes questioned in the literature, is demonstrated.

Animals↗
PubMed1987

Endogenous leukotriene D4 formation during anaphylactic shock in the guinea pig.

Experiments on the metabolism and excretion of i.v. administered selectively labeled [3H8]leukotriene C4 in bile duct-cannulated guinea pigs indicated predominantly biliary excretion of tritium. The major leukotriene metabolite in bile was identified as leukotriene D4. By monitoring leukotriene excretion radioimmunochromatographically, it was shown that guinea pigs suffering from anaphylactic shock produce leukotriene D4 endogenously. Immunological challenge of animals sensitized to ovalbumin was accompanied by an increase of biliary leukotriene D4 concentrations from 10 +/- 1 to 86 +/- 10 nM (mean +/- SEM, n = 5, P less than 0.001). When considering that bile flow was decreased to about half after challenge, the excretion rate of leukotriene D4 in bile increased from 0.88 +/- 0.16 before to 3.18 +/- 0.38 pmol X min-1 X kg-1 after challenge (mean +/- SEM, n = 5, P less than 0.002). It is concluded that systemic anaphylaxis in the guinea pig is associated with endogenous generation of leukotriene C4 (up to 1 nmol/kg during a 30-min period after the challenge.

Anaphylaxis↗
PubMed1987

T lymphocytes displaying major histocompatibility complex-unrestricted cytotoxicity after activation by K46M, a mitogenic monoclonal antibody against leucoagglutinin-reactive human T lymphocyte surface components.

Activation of human peripheral blood lymphocytes (PBL) with the mitogenic monoclonal antibody (MoAb) K46M, which recognizes 1-5% of PBL, resulted in the expansion of cells with cytolytic activity. Thus, after culture of the activated lymphocytes in medium containing interleukin 2 (IL-2), they lysed a variety of cultured cell lines. The majority of the activated lymphocytes reacted with MoAb to CD8, CD3, and to the T cell antigen receptor heterodimer (Ti) but not with antibodies to antigens expressed on natural killer (NK) cells. The cytotoxicity was not inhibited by MoAb to CD3 or Ti. However, the killing of K562, but not of other cell lines, was enhanced by three to four times in the presence of anti-Ti antibodies. Anti-CD3 or other control antibodies had no effect. Cold target inhibition experiments indicated that the cytolytic lymphocytes recognized closely related structures on the target cells. Phenotypically and functionally similar effector cells emerged after activation of PBL with the anti-CD3 MoAb OKT3. Taken together, the results indicate that activation of PBL with MoAb K46M induces cytotoxic cells that differ from classical NK cells but that resemble mature cytotoxic T lymphocytes (CTL). However, unlike CTL, cytotoxicity was not MHC-restricted and the conventional T-cell receptor complex (CD3/Ti) appeared not to be involved in target cell recognition and cytolysis.

Agglutinins↗
PubMed1987

Synergistic enhancement of mitogen responses of human lymphocytes by inhibitors of cyclo-oxygenase and 5,8,11-eicosatriynoic acid, an inhibitor of 12-lipoxygenase and leukotriene biosynthesis.

Blood mononuclear cells are well-known producers of various cyclo-oxygenase and lipoxygenase metabolites of arachidonic acid, some of which possess immunoregulatory functions. In the present investigation, we have examined 3H-thymidine incorporation in human blood lymphocytes cultured with polyclonal mitogens and antigens in the presence of various inhibitors of cyclo-oxygenase (such as indomethacin and meclofenamic acid) and an inhibitor of 12-lipoxygenase and leukotriene biosynthesis, 5,8,11-eicosatriynoic acid (ETI). It was observed that these inhibitors could augment mitogen responses of nonpurified lymphocyte preparations but not of preparations which were depleted of monocytes. The results indicate that monocytes and not lymphocytes were the main producers of immunosuppressive eicosanoids derived from arachidonic acid. Further, mitogenic responses in the presence of both an inhibitor of cyclo-oxygenase and ETI were augmented to a higher extent than expected. Again, this enhancement was not observed in preparations depleted of monocytes. Arachidonic acid metabolism was examined in mitogen-stimulated cultures pulsed with 14C-arachidonic acid. It was observed that the production of three metabolites was inhibited by meclofenamic acid, whereas the amounts of another 14Cr-labeled compound were almost doubled in the presence of meclofenamic acid.

8,11,14-Eicosatrienoic Acid↗
PubMed1987

Effects of some prostaglandins and leukotrienes on lymphocytes, monocytes and their activity in vitro.

The effect of some prostaglandins (PGs) and leukotrienes (LTs) on lymphocytes and monocytes was tested in vitro. Overnight incubation with PGD2 reduces the expression of Leu-2 antigen (suppressor/cytotoxic phenotype) and of Fc receptors for IgG. PGA2, PGD2 and to a lesser extent PGE2 inhibit PHA reactivity of lymphocytes. LTB4 does not have any inhibitory activity. Preincubation of lymphocytes with PGD2 and PGE2 decreases their NK activity. LTB4, but not the PGs tested, stimulates monocyte metabolism as assessed by chemiluminescence.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1986

Metabolism of leukotriene E4 by rat tissues: formation of N-acetyl leukotriene E4.

Leukotriene E4 was incubated with subcellular fractions from rat liver homogenates. A product identified as 5-hydroxy-6-S-(2-acetamido-3-thiopropionyl)-7,9-trans-11,14- cis-eicosatetraenoic acid (N-acetyl leukotriene E4) was formed. Enzymes catalyzing the reaction were associated with particulate fractions sedimenting between 600 and 8500 g and 20,000 and 105,000 g. Acetyl coenzyme A served as the donor of the acetyl group. N-Acetyl leukotriene E4 was also formed by the 105,000g sediment fractions from kidney, spleen, skin, and lung. The myotropic activity of N-acetyl leukotriene E4 on isolated guinea pig ileum was reduced over 100-fold compared to that of leukotriene D4.

Acetylation↗
PubMed1986

In vivo metabolism of leukotriene C4 in germ-free and conventional rats. Fecal excretion of N-acetylleukotriene E4.

[5,6,8,9,11,12,14,15-3H8]Leukotriene C4 was subcutaneously injected into rats. Substantial amounts of the administered radioactivity were excreted in feces of germ-free and conventional animals during a 72-h period (78 and 64%, respectively). Analyses of fecal extracts by high performance liquid chromatography showed eight radioactive components for each type of animal. One metabolite amounted to 4.6% of the injected radioactivity in germ-free and 0.6% in conventional rats. Its chemical structure, 5-hydoxy-6-S-(2-acetamido-3-thiopropionyl)-7,9-trans-11,14-c is-eicosatetraenoi c acid (N-acetylleukotriene E4) was determined by ultraviolet spectroscopy, fast atom bombardment mass spectrometry, chemical and enzymatic transformations, and confirmed by chemical synthesis. Another metabolite (2.7% of the administered radioactivity in germ-free and 0.5% in conventional rats) was characterized as the 11-trans isomer of the former metabolite. The pathway of formation of these compounds appears to be analogous to the pathway of mercapturic acid biosynthesis.

Animals↗
PubMed1986

Monoclonal antibodies against leucoagglutinin-reactive human T lymphocyte surface components. Two antibodies which inhibit cell-mediated cytotoxicity at a post-binding stage.

Two out of 20 monoclonal antibodies (IgM, kappa), mAb 3192 and mAb K3G, raised against leucoagglutinin-reactive components on human T cells, effectively blocked lymphocyte-mediated cytotoxicity in vitro. No antigenic polypeptide reactive with these antibodies has been identified thus far. However, they have previously been shown to react specifically with certain neutral glycolipids obtained from spleen. Both mAb inhibited the cytotoxicity of natural killer (NK) cells against K562 cells, antibody-dependent cellular cytotoxicity (ADCC) towards antibody-coated bovine erythrocytes and cytotoxic T lymphocyte activity against allogeneic target cells. In both NK and ADCC, preincubation of the lymphocytes with different antibody concentrations resulted in a dose-dependent reduction of cytotoxicity. In contrast, preincubation of the target cells had no effect indicating that the mAb inhibited cytotoxicity at the effector cell level. When studied at the single-cell level, the mAb did not alter the number of lymphocytes forming conjugates with K562 but significantly reduced the frequency of conjugates containing dead target cells. Addition of the mAb to preformed conjugates resulted in a dose-dependent reduction in the proportion of conjugates containing dead target cells. Furthermore, mAb 3192 did not reduce the number of lymphocytes forming rosettes with bovine erythrocytes, indicating that inhibition of ADCC was not due to blocking of the effector cell-target cell interaction mediated by the Fc receptor of the effector cells. Taken together, these results suggest that the mAb inhibited cytotoxicity by interfering with a post-binding step common for the different cytotoxicity systems.

Antibodies, Monoclonal↗