Search PubMed⌕ Search

Biomedical subjects

K Bendtzen

Publications and source records attributed to K Bendtzen.

At least 325 records · Page 18Linked to original sources
PubMed1982

Role of Zn2+ and other divalent metal ions in human lymphokine production in vitro.

The effects of phenanthroline and of various metal ions on human leucocyte migration inhibitory factor (LIF) production were studied. Previously reported preliminary data showed that phenanthroline, a divalent metal ion chelator, reduced the elaboration o LIF in a dose-dependent manner by specifically but not by non-specifically stimulated lymphocytes. This paper shows that suppression of LIF production caused by phenanthroline could be entirely reversed by Zn2+, Ni2+ and, most effectively, by Co2+. When a battery of divalent cations were tested for direct inhibitory effects on LIF production, Cd2+ and, to a lesser extent, Cu2+ were found to be effective. Again, only specifically stimulated cells were susceptible. This profile of responses resembles greatly that seen in experiments with carboxypeptidases, indicating that a carboxypeptidase-like, probably Zn2+-dependent enzyme is active during antigen-induced lymphokine production. This metalloenzyme may be derived from activated monocytes/macrophages and, like the lymphocyte-activating factor, exerts its activity in the G1 phase of the cell cycle.

Antigens↗
PubMed1982

Involvement of monokines in antigen- and lectin-induced human lymphokine production.

To analyze the role of monocytes/macrophages (Mø's) in the activation of human lymphocytes, suspensions enriched in T cells and markedly depleted of Mø's were prepared. The Mø-depleted cells challenged by tuberculin did not elaborate the lymphokine, leukocyte migration inhibitory factor (LIF). This reduction in LIF production was negatively correlated to the proportion of residual Mø's being complete in the presence of less than 2% Mø's. In contrast, the LIF response to the polyclonal activator, phytohemagglutinin A, was unimpaired by Mø depletion. LIF production of the Mø-depleted cells could be fully reconstituted by addition of conditioned media obtained from Mø cultures, especially if stimulated by the Mø-activating agent, phorbol myristate acetate. This effect was dose-dependent and could be ascribed to molecules of molecular weights 80K and 12K, respectively.

Antigens↗
PubMed1982

Functional characteristics of synovial fluid and blood mononuclear cells in rheumatoid arthritis and traumatic synovitis.

The activity of blood mononuclear cells (BMC) and synovial fluid mononuclear cells (SMC) from patients with rheumatoid arthritis (RA) and traumatic synovitis (TS) was assessed by means of [14C]thymidine incorporation and production of leukocyte migration inhibitory factor (LIF). When compared with normal controls, spontaneous LIF production by BMC was found in 5 of 9 TS patients, whereas spontaneous LIF production by rheumatoid arthritis BMC and by SMC from both patient groups was infrequently seen. ConA-induced LIF production by BMC and SMC from both patient groups did not differ significantly from that of normal controls. Thymidine incorporation by unstimulated SMC and BMC was low in both patient groups. After stimulation with polyclonal activators, SMC showed significantly reduced proliferation in comparison with BMC, but the responses to microbial antigens were equal to or higher than those of BMC. The proliferative responses of stimulated SMC from TS patients were higher than the responses displayed by stimulated SMC from RA patients.

Adult↗
PubMed1981

Induction of antigen-specific immunological unresponsiveness by inhibitors of human lymphocyte-activating factor.

Antigen-stimulated blood mononuclear cells preincubated in vitro with Cd2+ or phenanthroline, a Zn2+-chelator, did not respond normally on restimulation with antigen, as judged by their ability to elaborate leucocyte migration inhibitory factor (LIF). Other divalent metal ions, including Zn2+, were ineffective. The effect was immunologically specific, since challenge of similarly pretreated cells with an unrelated antigen, to which the cells were also sensitized, resulted in normal LIF production. The lack of responsiveness could not be ascribed to cell death, carry-over of the inhibitors, or exhaustive release of LIF during the inductive phase. Phenanthroline and Cd2+ are known to inhibit the activity of the macrophage-derived lymphocyte-activating factor (LAF), whose effect is exerted non-specifically on antigen-stimulated lymphocytes in G1. Seen in the context of a two-signal model of lymphocyte activation, it is hypothesized that immediate tolerance induction is triggered by delivery of the antigenic stimulus (signal 1) without addition of the non-specific signal 2 (LAF).

Cadmium↗
PubMed1980

Differential role of Zn2+ in antigen- and mitogen-induced lymphokine production.

The effect on human lymphokine production in viro of phenanthroline, a Zn2+-chelating agent and an inhibitor of carboxypeptidases A and B, was tested. The elaboration of leucocyte migration inhibitory factor (LIF) by tuberculin-sensitized mononuclear cells stimulated with the specific antigen was reduced in a dose-dependent manner, an effect completely restored by addition of excess Zn2+. In contrast, phenanthroline did not affect LIF production by mononuclear cells activated nonspecifically by phytohaemagglutinin. It is hypothesized that the presence of a Zn2+-dependent molecule, possibly a carboxypeptidase, may be necessary for antigen- but not for mitogen-induced lymphokine production.

Antigens↗
PubMed1980

Inflammatory, non-antibody lymphocytic mediators (lymphokines).

This paper is a survey of some of the best characterized non-antibody lymphocytic mediators (lymphokines). Special emphasis is laid on the description of the molecular biology of human inflammatory and antigen-nonspecific lymphokines, and where clinical relevant their methods of assay are summarized. The putative role of lymphokines in vivo is briefly discussed.

B-Lymphocytes↗
PubMed1980

Use of benzoyl-L-phenylalanyl-L-valyl-L-arginine (3H) methyl ester as a sensitive and selective substrate for the human lymphokine, leukocyte migration inhibitory factor (LIF).

Human leukocyte migration inhibitory factor (LIF) appears to be a serine esterase and protease exhibiting specific affinity towards arginine esters and amides. On the basis of indirect evidence that an amide of the oligopeptide benzoyl-phenylalanyl-valyl-arginine might have high and selective affinity for LIF, we prepared an ester of this oligopeptide, benzoyl-phenylalanyl-valyl-arginine (3H) methyl ester (3H-BPVAME) for the direct measurement of LIF activity in a double-phase radio-enzyme assay. The hydrolysis of 3H-BPVAME followed enzyme-substrate kinetics in that the reaction was time-, temperature-, pH-, and concentration-dependent. 3H-BPVAME rpoved to be more selective and approximately 20 times more sensitive as a substrate for LIF than previously used radiolabeled substrates such as 3H-BAEE and 3H-TAME. Moreover, hydrolysis of 3H-BPVAME by partially purified LIF preparations was significantly inhibited by 10(-8) to 10 (-5) M of guanosine 3',5'-cyclic monophosphate (cGMP), further supporting the hypothesis that cGMP acts as a regulator of LIF activity. Inhibition of LIF-induced esterolysis was also provided by dibutyryl cGMP, but only at concentrations 10(-7) to 10(-5) M; 8-bromo cGMP and adenosine 3',5'-cyclic monophosphate were both ineffective. These results provide support for the use of 3H-BPVAME as a more selective substrate to detect esterase activity in LIF preparations than heretofore described and the possible development of a biochemical assay for the measurement of this lymphokine.

Cyclic AMP↗
PubMed1979

Leukocyte migration inhibitory factor: a serine esterase released by stimulated human lymphocytes. Kinetic analysis and inhibition by cyclic GMP.

Lymphocytes, stimulated with concanavalin A, release small amounts of non-immunoglobulin, highly reactive proteins called lymphokines. One of these, a serine esterase, termed leukocyte migration inhibitory factor according to its function in vitro, is found in supernatants of stimulated human lymphocytes at concentrations less than 1 ng/ml. The esterase was purified in good yield and its esterolytic activity was measured by a sensitive radioenzymic assay. The kinetics of the esterolytic activity were studied and the effect of various nucleotides examined. Competitive inhibition of esterolysis was seen with cyclic GMP at concentrations down to 10(-7) M, and with 2',3'-cyclic CMP at a concentration of 10(-3) M. A role of this esterase, not only as a mediator acting upon polymorphonuclear leukocytes, but also as an intracellular regulator of lymphocyte activation, is discussed.

Concanavalin A↗
PubMed1979

Increased polymorphonuclear leukocyte cGMP levels induced by the human lympholine, leukocyte migration inhibitory factor (LIF).

The possible involvement in vitro of 3', t'-cyclic GMP (cGMP) in the mechanism of action of the lymphokine, leukocyte migration inhibitory factor (LIF), was investigated. Partially purified LIF-rich supernatants, but not their control counterparts, induced a 2-fold increase in the cGMP levels of purified human polymorphonuclear (NMN) leukocytes. The effect was no influenced by heat-inactivated horse serum; it was manifested within 3 min of exposure to LIF and it subsided within 180 min. LIF and the supernatant factor responsible for the cGMP-generating effect were both rendered inactive by treatment with the serine esterase and protease inhibitor, phenylmethylsulfonyl fluoride, indicating that these factors are closely related, if not identical. A potent phosphodiesterase inhibitor, dipyridamole (2 x 10(-4) M), induced a 3- to 5-fold increase in PMN leukocyte cGMP levels, but combined treatment with purified LIF and dipyridamole did not add to this effect. This suggests that the cGMP-generating factor acts on the biochemical pathway that degrades cGMP.

Cyclic GMP↗
PubMed1979

Substrate specificity of the human lymphokine leucocyte migration-inhibitory factor (LIF): radioenzymic assay and inhibition by cGMP.

The human lymphokine, leucocyte migration-inhibitory factor (LIF), appears to be a serine esterase and protease by virtue of its susceptibility to the irreversible enzyme inhibitor, phenylmethylsulfonyl fluoride (PMSF), and by the ability of arginine esters and amides to protect LIF against PMSF-induced inactivation. In this paper, three methods are described by which putative substrates for LIF may be investigated. Thus, molecules satisfying the substrate specificities of this lymphokine should (1) protect LIF against inactivation by PMSF, (2) reduce LIF activity in vitro on polymorphonuclear leucocytes, and (3) reduce the esterolytic activity of purified LIF-rich supernatants. The first two reactions were tested by means of the leucocyte migration agarose technique; the third reaction was tested by a sensitive enzyme assay using tritiated tosyl arginine methyl ester as substrate. Guanosine 3',5'-cyclic monophosphoric acid, which is capable of protecting LIF against PMSF-induced inhibition, also inhibited the esterolytic activity of the purified LIF preparation. Four synthetic oligopeptide substrates for trypsin, thombin and plasmin were investigated. Only one, the thrombin- and trypsin-specific benzoyl-phenylalanyl-valyl-agarine-p-nitroanilide, possessed high affinity for the LIF molecule and may therefore prove to be a potent substrate for this lymphokine.

Anilides↗
PubMed1979

Determination of the human lymphokine leukocyte migration inhibitory factor (LIF) by a sensitive radioenzymatic assay. Inhibitory effect of cGMP on the esterolytic activity of highly purified LIF.

Indirect experiments using irreversible enzyme inhibitors have shown that the human lymphokine leukocyte migration inhibitory factor (LIF) is a serine esterase and protease exhibiting specific affinity towards arginine esters and amides. A sensitive assay for direct measurement of esterase activity using p-tosyl-L-arginine (3H) methyl ester (3H-TAME) as substrate is described. Esterolytic activities are demonstrated in crude supernatants of human lymphocytes stimulated with concanavalin A (LIF-rich) and, more pronounced, in supernatants of unstimulated cells (control). To follow the effects of purification procedures, the serine esterases of LIF-rich and control preparations were specifically labeled with the irreversible, active site directed agent (1,3-3H)di-isopropylphosphorofluoridate. Most of these enzymes, visualized by Sephadex chromatography, were removed by a gentle three-step procedure, allowing at least 50% of the initial LIF activity to be recovered. The resulting LIF-rich preparation, purified to contain serine esterases at a concentration corresponding to less than 1 ng per ml original supernatant, still showed estrolytic activity towards 3H-TAME. The optimal conditions for the radioenzymatic assay of purified LIF and the inhibitory effect of 10(-4) M cGMP, which on the basis of indirect experiments has been implicated as a specific regulator of LIF activity, are described.

Affinity Labels↗
PubMed1978

Human leucocyte migration inhibitory factor (LIF). V. Specific regulation of the lymphokine serine protease activity by 3',5'-cGMP and, possibly, 2',3'-cCMP.

The cyclic nucleotides guanosine 3',5'-cyclic monophosphoric acid (3',5'-cGMP) and cytidine 2',3'-cyclic monophosphoric acid (2',3'-cCMP) but not cyclic phosphodiesters derived from the bases adenine and uracil preserved LIF activity against the blocking effect of the serine protease inhibitor phenylmethylsulphonyl fluoride (PMSF). Phosphomonoesters derived from guanosine and cytidine as well as 2',3'-cGMP and 3',5'-cCMP were all inactive, indicating specificity for phosphodiester bonds and their respective positions in the two active nucleotides. The protection afforded by 3',5'-cGMP and 2',3'-cCMP was dose dependent. Thus, using 10(-3) M PMSF, 3',5'-cGMP was active at concentrations higher than 10(-5) to 10(-4) M, and 2',3'-cCMP at concentrations higher than 3 X 10(-4) to 10(-3) M. The more pronounced LIF-inhibitory effect obtained by increased concentrations of PMSF could be overcome by raising the levels of the nucleotides, indicating that the interactions between PMSF and the nucleotides with LIF were mutally exclusive. The possibility that 3',5'-cGMP and perhaps 2',3'-cCMP function as modulators of LIF is discussed, and models for the function of this lymphokine are proposed.

Cell Migration Inhibition↗