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Biomedical subjects

K Bendtzen

Publications and source records attributed to K Bendtzen.

At least 343 records · Page 19Linked to original sources
PubMed1978

Immunological studies in thymectomized and non-thymectomized patients with myasthenia gravis.

Eleven thymectomized and ten non-thymectomized patients with myasthenia gravis, matched with respect to sex, age, duration and severity of the disease were investigated with respect to routine clinical features, electrophysiological examination, HLA-typing, auto-antibodies, lymphocyte subpopulations in peripheral blood, Concanavalin A-induced release of leucocyte migration inhibitory factor (LIF), in vitro lymphocyte activation by mitogens and antigens and response to primary immunization with dinitrochlorobenzene measured in vivo and in vitro. The following conclusions could be drawn. The immune response to external antigens seems to be normal in myasthenia gravis and thymectomy is not followed by general defects in immune competence; at least as investigated by current techniques. The only reduction of responsiveness demonstrable in the thymectomized group was a decreased release of LIF by Concanavalin A-stimulated lymphocytes. Primary immune responses appear to be increased after adult thymectomy, which may be due to a decrease in suppressor T-lymphocyte activity. A hypothesis is formulated that Concanavalin A-induced release of LIF may reflect the competence of suppressor T-lymphocytes in man.

Adolescent↗
PubMed1978

Production of leucocyte migration inhibitory factor (LIF) in infectious mononucleosis. Spontaneous release and lack of response to concanavalin A.

The spontaneous release of LIF from blood lymphocytes was studied in patients with infectious mononucleosis. Mononuclear cells were separated from the blood and cultured for 22 hr, and LIF activity in the supernatant was determined. Supernatants depleted of LIF activity by means of anti-LIF antibodies or by treatment at 80 degrees C for 30 min were employed as controls; these two methods gave essentially similar results. In nine out of eighteen patients, spontaneous LIF production was demonstrated during the acute stage of the illness; this was not seen in any of the normal persons studied. 6 weeks later, spontaneous LIF production had ceased in most patients. Concanavalin A stimulated all normal lymphocytes to LIF production, but in sixteen out of seventeen patients with infectious mononucleosis this response was absent or diminished. At the follow-up study 6 weeks later, the lymphocyte response to concanavalin A was still suppressed.

Adolescent↗
PubMed1977

Human leukocyte migration inhibitory factor (LIF). I. Effect of synthetic and naturally occurring esterase and protease inhibitors.

The activity of leukocyte migration inhibitory factor (LIF) obtained from Sephadex-G-100-chromatographed supernatants of concanavalin-A-stimulated human lymphocytes was suppressed by two synthetic serine esterase and serine protease inhibitors (di-isopropylfluorophosphate (DFP) and phenylmethylfulfonyl fluoride (PMSF)). LIF activity was also reduced by the naturally occurring protease inhibitors soybean trypsin inhibitor and aprotinin. The observed effect of DFP and PMSF was irreversible, since elimination of the inhibitors by dialysis did not restore LIF activity. The effect of PMSF was dose-, time-, and temperature-dependent, and hydrolytic products of PMSF as well as sodium fluoride were inactive in blocking LIF. These results suggest that LIF may act as a serine esterase or a serine protease, or both of these, and that this putative enzyme is present in an activated form in supernatants from mitogen-stimulated mononuclear cells.

Aprotinin↗
PubMed1977

Human leukocyte migration inhibitory factor (LIF). II. Partial biochemical characterization of the substrate specificities for this lymphokine.

Previously reported experiments suggested that an esterase or a protease, or both, might participate in the expression of human leukocyte migration inhibitory factor (LIF). To clarify this further, a wide variety of simple ester were tested for the ability to protect LIF against inactivation by the serine esterase inhibitor phenylmethylsulfonyl fluoride (PMSF). alpha-N-benzoyl-L-arginine ethylester (BAEE), a typical trypsin substrate, and bis-p-nitrophenyl phosphate (BNPP), a phosphodiester, were the only esters capable of retaining LIF activity in the presence of PMSF. Agents chemically closely related to these esters were inactive. Moreover, the protection afforded by BAEE and BNPP was the king that would be anticipated if the esters and irreversible inhibitor competed for the same site on LIF. Baee and BNPP also protected against inactivation by di-isopropylfluorophosphate (DFP), another irreversible serine esterase inhibitor. In addition, LIF-treated leukocytes partly escaped migration inhibition in the presence of BAEE and BNPP, respectively. These results indicate that human LIF contains a serine residue necessary for lymphokine activity. It is still not proved, however, that LIF as an enzyme is capable of hydrolyzing BAEE and BNPP, although it seems highly possible. The substrate specificities of a putative LIF enzyme are discussed on the basis of the chemical structure of BAEE and BNPP.

Benzyl Compounds↗
PubMed1977

In vitro modulation of human leucocyte migration and migration inhibitory factor (LIF) activity by cyclic 3',5'-AMP and cyclic 3',5'-GMP.

The effects of cyclic 3', 5'-AMP (cAMP) and cyclic 3', 5'-GMP (cGMP) on the in vitro migration of human peripheral blood leucocytes under agarose and on the activity of leucocyte migration inhibitory factor (LIF) was studied. Leucocyte migration was not influenced by dibutyryl cAMP, while the dibutyryl derivative of cGMP significantly stimulated cell migration (1 x 10(-5)M). LIF-treated leucocytes partially escaped migration inhibition in the presence of dibutyryl cAMP (greater than or equal to 1 x 10(-6)M), while dibutyryl cGMP was inefficient. If the parent compounds cAMP and cGMP were tested, almost similar results would be obtained, although at higher concentrations of the drugs. These results represent initial experiments with a view to investigating the possible role of cyclic nucleotides in the expression of LIF activity.

Bucladesine↗
PubMed1977

Effect of human leucocyte migration inhibitory factor (LIF) on 3', 5'-cyclic AMP levels of peripheral blood leucocytes.

The possible involvement of 3', 5'-cyclic AMP (cyclic AMP) in the mechanism of action of leucocyte migration inhbitory factory (LIF) was tested. LIF-treated human peripheral blood leucocytes were incubated at 37 degrees C for various times between 0 and 22 h. The concentrations of cyclic AMP in these cultures did not differ from those in controls. Furthermore, LIF did not affect the cellular release of cyclic AMP. Neither when testing purified neutrophils, which are the prime targets of LIF action, an effect of LIF was found. Cyclic AMP levels decreased with time of incubation, whether testing mononuclear cells (92 per cent lymphocytes), purified neutrophils (98 per cent), or buffy coat cells (72 per cent neutrophils; 22 per cent lymphocytes). However, a transient and as yet unexplained increase in the cyclic AMP levels of the latter mixed population of cells was manifested within 10 to 30 min of incubation.

Cells, Cultured↗
PubMed1977

Human leukocyte migration inhibitory factor (LIF). IV. 3',5'-cGMP protects LIF against inactivation by the esterase inhibitor phenylmethylsulfonyl fluoride.

Recently reported experiments suggest that human leukocyte migration inhibitory factor (LIF) has properties of an esterase and a protease with substrate specificities directed against arginine esters and amides. Also reported previously, the synthetic phosphodiester bis-p-nitrophenyl phosphate (BNPP) but not various phosphomonoesters preserve LIF activity in the presence of the serine esterase inhibitor phenylmethylsulfonyl fluoride (PMSF). In this paper I demonstrate that guanosine 3'5'-cyclic monophosphoric acid (3',5'-cGMP), a naturally occurring phosphodiester, at concentrations in excess of 10(-5)M also protects LIF against PMSF inactivation. The effect seems specific for the diester bond, its position in the nucleotide, and the guanine base. The possibility that LIF may be a multifunctional or an allosteric enzyme regulated by 3',5'-cGMP is discussed.

Cyclic AMP↗
PubMed1977

Human leukocyte migration inhibitory factor (LIF). I. Effect of synthetic and naturally occurring esterase and protease inhibitors.

The activity of leukocyte migration inhibitory factor (LIF) obtained from Sephadex-G-100-chromatographed supernatants of concanavalin-A-stimulated human lymphocytes was suppressed by two synthetic serine esterase and serine protease inhibitors (di-isopropylfluorophosphate (DEP) and phenylmethylsulfonyl fluoride (PMSF)). LIF activity was also reduced by the naturally occurring protease inhibitors soybean trypsin inhibitor and aprotinin. The observed effect of DFP and PMSF was irreversible, since elimination of the inhibitors by dialysis did not restore LIF activity. The effect of PMSF was dose-, time-, and temperature dependent, and hydrolytic products of PMSF as well as sodium fluoride were inactive in blocking LIF. These results suggest that LIF may act as a serine esterse or a serine protease, or both of these, and that this putative enzyme is present in an activated form in supernatants from mitogen-stimulated mononuclear cells.

Aprotinin↗
PubMed1977

Human leukocyte migration inhibitory factor (LIF) III. Further investigations on the serine protease nature of this lymphokine and its preference for arginine amides.

Previous findings suggesting an esterase and protease nature of human leukocyte migration inhibitory factor (LIF) were extended by testing the ability of different protease and esterase inhibitors to reduce LIF activity. The serine-specific inhibitors phenylmethylsulfonyl fluoride (PMSF) and physostigmine (eserine) markedly reduced LIF activity, whereas the histidine-specific inhibitors N-tosyl-L-lysine chloromethyl ketone (TLCK) and L-tosylamide-2-phenylethyl chloromethyl ketone (TPCK) were inactive. That LIF might act as an esterase and a protease was further strengthened by the ability of pralidoxime methansulfonate (2-PAM) to reestablish LIF activity of supernatants previously inactivated by PMSF. Furthermore, the arginine amides N-benzoyl-L-arginine-p-nitroanilide (BApNA) and N-benzoyl-L-phenylalanyl-L-valyl-L-arginine-p-nitroanilide (BPVApNA) were shown to satisfy the substrate specificities of the putative LIF enzyme. Indeed, BPVApNA seemed to possess a particularly strong affinity for LIF, indicating its potential role in an enzymatic LIF assay.

Amides↗
PubMed1977

Leucocyte migration inhibitory activity of concanavalin-A-stimulated lymphocytes. In vivo and in vitro modifications with dipyridamole and acetylsalicylic acid.

Lymphocytes from 14 patients treated with a combination of acetylsalicylic acid (ASA) and dipyridamole (DIPY) showed a decreased ability to produce leucocyte migration inhibitory activity (LMIA) when stimulated with concanavalin-A (ConA). The combined treatment also produced a decrease of leucocyte response to a standard LMIA-containing culture supernatant. Treatment with only one of the two drugs did not cause detectable alteration of the lymphocyte response to Con-A or the leucocyte response to LMIA. In vitro, both DIPY and ASA were independently effective in decreasing the LMIA production of Con-A-stimulated lymphocytes and the leucocyte response to a standard LMIA-containing culture supernatant.

Adult↗
PubMed1976

Partial purification of human leucocyte migration inhibitory factor (LIF) by immunosorption of supernatant protein contaminants detected by crossed immunoelectrophorsis.

Concentrated supernatants from washed human lymphocytes incubated in serum-free medium were investigated by crossed immunoelectrophoresis. Quantitatively, the most important macromolecules were serum proteins, in particular albumin and degraded products of albumin. No gross difference was detectable between supernatants from concanavalin A stimulated and unstimulated lymphocytes. The degraded proteins were considered to arise as a result of proteolytic enzymes present in both stimulated and unstimulated lymphocyte supernatants. These molecules exhibited almost the same electrophoretic mobility and molecular weight as native albumin, and might therefore be expected to be difficult to separate from some lymphokines by conventional biochemical techniques. Rabbit immunoglobulins to whole human serum proteins together with immunoglobulins against crude supernatants of mitogen stimulated lymphocytes were therefore bound covalently to an agarose matrix. This preparation efficiently removed all detectable proteins from concentrated supernatants of activated lymphocytes as determined by crossed immunoelectrophoresis. Leucocyte migration inhibitory factor (LIF) was recovered almost quantitatively, and a 40-fold purification of LIF was achieved. The technique is rapid, economical and well suited as an initial step for purification of large quantities of LIF.

Animals↗
PubMed1976

Leucocyte migration inhibitory activity of concanavalin-A-stimulated human lymphocytes. Modification by dipyridamole, lysine-acetylsalicylate and heparin.

The in vitro effects of heparin, dipyridamole (DIPY) and lysine-acetylsalicylate (LASA) on human peripheral blood leucocyte migration and upon production/release and effect of leucocyte migration inhibitory activity (LMIA) from lymphocytes stimulated with concanavalin-A (con-A) have been studied. The final concentration of each drug was of the same order of magnitude as during clinical treatment. The leucocyte migration under agarose was significantly increased by DIPY at a concentration of 100 mug/ml. The release/production of LMIA was inhibited by DIPY at 1 mug/ml and by LASA at 0.3 mug/ml. Heparin had no influence on LMIA release, even at 10 IU/ml. The LMIA of supernatants from con-A-stimulated lymphocyte cultures was inhibited by DIPY at a concentration of 10 mug/ml, by LASA at 3 mug/ml and by heparin at 10 IU/ml. The findings suggest that DIPY and LASA could have a dual role as modifiers of inflammation: 1) the well known role as antiaggregants tending to limit and impede thrombosis, and 2) as antagonists to the lymphocyte-mediated (type IV) immune reaction through a depressive action on lymphokine production/release and activity.

Aspirin↗
PubMed1976

Human leucocyte migration inhibition.

Within the last decade a variety of techniques have been developed and used for the detection of cell-mediated immunity in man by means of leucocyte migration inhibition in vitro. A detailed description of the leucocyte migration capillary tube technique (LMCT) and the leucocyte migration agarose technique (LMAT) is given. The procedure for selecting and using the proper antigen concentration is described. A description is also given of the indirect LMAT and the technique for determination of concanavalin A-induced lymphocyte release of leucocyte migration inhibition factor. Applications of these techniques are mainly intended for the exploration of the immunobiology of lymphocytes and cellular interactions associated with the immune response and the investigation of clinical conditions in man, i.e. infectious diseases, autoimmune diseases, transplantation states, tumour diseases, contact hypersensitivity and immunological deficiency states. Selection and adaptation to suit the experimental aim is necessary to obtain optimal results with these techniques. Their usefulness may be increased through more extensive use of purified antigens and indirect assays.

Cell Migration Inhibition↗
PubMed1976

Some physicochemical properties of human leucocyte migration inhibitory factor (LIF).

Leucocyte migration inhibitory factor (LIF) obtained from human lymphocytes stimulated with concanavalin A was consistently and irreversibly blocked by the serine-esterase inhibitor phenyl-methyl sulphonylfuoride (PMSF). This effect was not due to fluoride ions, hydrolysis products of PMSF or to impurities. PMSF pulse treatment of human buffy coat cells did not affect cell migration under agarose. LIF was also irreversibly destroyed by treatment with L-cysteine and 2-mercapto-ethanol, suggesting that the molecule contains disulphide linkage groups decisive for its configuration and biological activity. Di-sodium EDTA completely inhibited LIF activity but only if present during the entire migration period. Removal of EDTA before LIF assay restored LIF activity. Leucotye migration was neighter influenced by L-cysteine nor by EDTA. LIF activity was slightly diminished after treatment at 56 degrees C for 1 h and completely lost at 80 degrees C for 1/2 h. Furthermore, LIF appeared rather stable when treated at pH values between 4 and 11. These findings suggest, but do not prove, an esterase or a protease nature of human LIF.

Concanavalin A↗