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Biomedical subjects

T E Michaelsen

Publications and source records attributed to T E Michaelsen.

At least 109 records · Page 6Linked to original sources
PubMed1984

Inhibition or acceleration of fibrin polymerization by monoclonal immunoglobulins and immunoglobulin fragments.

A prolongation of the thrombin clotting time by at least 25% was found in the presence of 8 of 26 IgG myeloma proteins, 2 of 5 IgA proteins and 1 of 10 macroglobulins, in a concentration of 10 mg/ml. Normal pooled immunoglobulin in concentrations up to 83 mg/ml were inactive. 2 IgG and 2 IgM monoclonal immunoglobulins caused an acceleration of the thrombin time by at least 20%; this phenomenon has not been reported before. Corresponding results were obtained with these proteins when the polymerization of des-AA and des-AABB fibrin monomers were investigated in a light scattering system. Studies with enzymatically produced Fab, F(ab')2 and Fc fragments from normal and monoclonal immunoglobulin suggested that the polymerization inhibitory activity resides in the Fab portion of the immunoglobulin molecule. While the ability to inhibit fibrin polymerization may be an immunoglobulin specific effect, the acceleration caused by certain other monoclonal immunoglobulins may be an unspecific effect similar to that seen with dextran or albumin.

Animals↗
PubMed1984

Antigenic similarities both inside and outside the carbohydrate-binding sites of two-chain and one-chain leguminous lectins.

Antibodies were made against the two-chain lectin Lath-O from the seeds of Lathyrus odoratus as well as its isolated light (alpha) and heavy (beta) chains. These antibodies were used to antigenically compare the Lath-O with other two-chain lectins like Lath-S, lentil and Vicia cracca glc specific and with one-chain lectins like Con A, PHA, peanut and soybean. Sensitive ELISA tests showed that there was a distinct antigenic cross-reaction between the one-chain and two-chain lectins both by using antibodies against Lath-O whole molecules and its isolated beta-chains, while the anti-Lath-O alpha-chain antibodies barely reacted at all even with Lath-O alpha-chains. The antibodies against Lath-O whole molecules also strongly inhibited the mitogenic responses induced by two-chain lectins. Antibodies reacting inside the carbohydrate-binding site of the lectins were isolated by eluting them with glucose from lectin-Sepharose columns and antibodies reacting outside the carbohydrate-binding site were subsequently eluted with guanidine or buffer with low pH. The two antibody fractions were separately used to antigenically compare one-chain and two-chain lectins, demonstrating that both kinds of antibodies showed cross-reaction between one-chain and two-chain lectins. Both the antibodies presumably reacting inside the carbohydrate-binding site of the lectins and those reacting outside the carbohydrate-binding site inhibited haemagglutination activity of two-chain lectins, while haemagglutination by one-chain lectins was unaffected. The carbohydrate-binding site specificity of the glucose-eluted antibodies was assessed by glucose-inhibition in ELISA tests. Furthermore, galactose neither inhibited in these tests nor eluted antibodies from lectin-Sepharose columns. Control experiments were also performed with normal rabbit IgG.

Animals↗
PubMed1983

Differentiation antigens in human T-cell activation: evidence that anti-VH antibodies react with a membrane structure on human T lymphocytes distinct from the antigens detected by monoclonal antibodies of the OKT and Leu series.

The effect of a panel of monoclonal antibodies and heteroantibodies on T-cell proliferation in various assay systems has been examined. The antibodies tested were directed against T-cell differentiation antigens, HLA-DR antigens, and structures defined by an anti-human VH antiserum. As the test cell system highly purified subpopulations of T-cell growth factor (TCGF)-dependent T-cell lines activated either by mitogen or antigen were used. A survey of the data indicates the following: (1) Mitogenic and antigenic triggering of T lymphocytes are mediated through partly different membrane structures. (2) Antigenic stimulation by purified protein derivative (PPD) as well as polyclonal activation induced by OKT3/anti-Leu 4 monoclonal antibodies can be inhibited by heteroantibodies raised against human immunoglobulin VH fragments thus pointing to a possible connection between the antigens detected by these antisera. (3) There does not seem to be differences between the two major subpopulations of T lymphocytes (i.e., helper/inducer and suppressor/cytotoxic cells) as to how they respond to antigens or mitogens in the investigated assay systems. (4) A clear distinction was found between T blasts specific for PPD and allogeneic cells as compared to cytotoxic T cells (CTL), as the T4 and T8 antigens seem to be functionally important for antigen recognition among CTL but not for the blasts proliferating in response to PPD and allogeneic cells. (5) An inhibitory effect of OKT3/anti-Leu 4, OKIa1, and anti-HLA-DR on TCGF-dependent growth was detected, possibly indicating a steric relationship between these antigens and TCGF receptors on mitogen-induced T blasts. (6) Soluble factors obtained after incubating adherent cells with OKIa1 and anti-HLA-DR antibodies seemed to have an inhibitory effect on overall T-cell proliferation stressing the importance of studying the T-cell activation process at different levels in these kinds of experiments. (7) The results further suggest a complexity in the build up of antigen receptors on the various T-effector cells, perhaps also involving receptors for growth factors, HLA-DR antigens, and receptors for the latter.

Antibodies, Monoclonal↗
PubMed1983

H NMR studies of the Fc region of human IgG1 and IgG3 immunoglobulins: assignment of histidine resonances in the CH3 domain and identification of IgG3 protein carrying G3m(st) allotypes.

A 1H NMR study of the Fc region of human IgG1 and IgG3 immunoglobulins is presented. 1H NMR data were collected for the Fc and pFc' fragments obtained from human monoclonal IgG1 and IgG3 and also from rabbit IgG. The C2-H proton signal of His-435 in the CH3 domain of IgG1 was assigned by comparing the spectra of the Fc fragment of IgG1 with that of IgG3 [G3m(g)] where there is a substitution of histidine by arginine at position 435. Chemical shifts and linewidths of the His-435 signal are quite different for the Fc and pFc' fragments. We suggest that His-435 is involved in the interdomain CH2-CH3 contact. Assignments of the C2-H proton signals of His-429 and His-433 in the CH3 domain were made on the basis of our previous 1H NMR results on the human light chain. NMR measurements clearly show that IgG3 Jir, which was isolated from a Japanese patient with cryoglobulinemia, has histidine at position 435 as in the case of IgG1. We also confirmed that IgG3 Jir reacts strongly with protein A. In marked contrast, IgG3 [G3m(g)] does not bind protein A. These results show that binding of protein A to the Fc region is not subclass-specific and the existence of His-435 is a necessary condition for the protein A binding. It has recently been demonstrated that IgG3 proteins carrying G3m(st) allotypes, which are relatively common in Mongoloid populations but quite rare in Caucasians, bind protein A strongly. We confirmed that, as expected, IgG3 Jir carries G3m(st) allotypes. The pH titration curve of His-435 observed for IgG3 Jir is quite different from that for IgG1. This result makes it possible to identify by 1H NMR IgG3 proteins carrying G3m(st) allotypes. In the case of the pFc' fragments, His-435 gives identical titration curves for IgG1 and IgG3 [G3m(st)]. This is consistent with the fact that no serological distinction can be made between the pFc' fragments obtained from these two types of proteins. We suggest that G3m(st)-specific antiserum differentiates IgG1 and IgG3 [G3m(st)] by recognizing the difference in the way in which the CH2 and CH3 domains make contact with each other.

Animals↗
PubMed1983

Interactions of purified human ceruloplasmin with Lathyrus odoratus, Lens culinaris and Canavalia ensiformis lectins.

Human ceruloplasmin was isolated from normal serum by fractional polyethylene glycol precipitation and subsequent ion exchange chromatography. The molecular mass determined by ultracentrifugation was 132 kDa and an optical density ratio (A610/A280) of 0.046 was observed in the preparation. Immunoelectrophoresis, agarose-gel electrophoresis and N-terminal amino-acid sequence analyses showed that the ceruloplasmin preparation was highly purified, while dodecyl sulphate polyacrylamide-gel electrophoresis indicated some degradation of the protein. Affinity chromatography showed that only a fraction of ceruloplasmin was bound to Lens culinaris or Lathyrus odoratus lectin-Sepharose, whereas nearly all the protein was bound to Canavalia ensiformis lectin-Sepharose. The carbohydrate composition of the ceruloplasmin fractions was analysed. It is suggested that fucose might be a determinant for the microheterogeneity in the carbohydrate chains of ceruloplasmin.

Amino Acid Sequence↗
PubMed1983

Properties of a lectin purified from the seeds of Cicer arietinum.

A lectin was isolated from seed extracts of Cicer arietinum by (NH4)2SO4 precipitation and subsequent ion exchange chromatography and gel filtration. Affinity chromatography on desialylated human IgM coupled to AH-Sepharose was also performed, but the amount bound was very low. The lectin has a molecular mass of about 44000 Da, as determined by ultracentrifugation and gel filtration. Dodecyl sulphate polyacrylamide-gel electrophoresis showed one band corresponding to a molecular mass of 26000 Da. N-Terminal amino acid sequence analyses indicate only one type of chain, suggesting that the lectin is probably dimeric. The amino acid composition is given. Papainized human erythrocytes of the different ABO groups were agglutinated equally well by the Cicer lectin, whereas untreated cells reacted weakly and only in the presence of bovine serum albumin. Simple sugars did not inhibit the agglutination, but some glycoproteins did inhibit. The lectin is probably nonmitogenic against human lymphocytes. Antigenic analyses in an enzyme-linked immunosorbent assay (ELISA) showed only a weak cross-reaction between Cicer and the lectins in the Vicieae tribe. Thus, our physicochemical and antigenic studies of the Cicer lectin support the botanical reasons recently given for removing the genus Cicer from the Vicieae tribe.

Amino Acid Sequence↗
PubMed1982

Neurosyphilis: intrathecal synthesis of oligoclonal antibodies to Treponema pallidum.

Oligoclonal IgG was present in the cerebrospinal fluid (CSF) of each of three patients with neurosyphilis studied. Conventional serological tests disclosed reduced serum/CSF ratios of antibodies to Treponema pallidum (TP) in each patient, consistent with intrathecal production of treponemal antibodies. Antibody analyses of electrofocused specimens by an immunofixation technique disclosed intrathecal production of oligoclonal TP antibodies in all patients. Treponemal antibody light chains showed a close correlation with the light chains of the oligoclonal CSF IgG. Absorption of the CSF with TP caused removal of the oligoclonal IgG. The results provide strong evidence that the oligoclonal CSF IgG in neurosyphilis represents TP antibodies, reflecting a specific immune response in the central nervous system to the infectious agent.

Aged↗
PubMed1982

Characterization of an antibody to factor VIII in a patient with acquired hemophilia with circulating immune complexes.

A 73-year-old previously healthy woman was admitted because of severe bleeding from esophagitic lesions and intraabdominal bleeding following hysterectomy. Acquired hemophilia, probably due to an IgG antibody to factor VIII (64 inhibitor units/ml) was noticed, the VIII:C in the patient's plasma being 18% or normal. Immune complexes isolated by polyethylene glycol precipitation had only a weak factor VIII inhibiting activity whereas IgG purified from the complexes and monomeric IgG present in her plasma exerted a strong inhibition. Removal of the complexes from plasma had no effect on the inhibitor titer thus indicating that only a minor part of the antibody was circulating as immune complexes. Plasma or purified IgG from the patient decreased the VIII:C of normal plasma to 18 og 14%, respectively, total inhibition being impossible to achieve even in antibody excess, probably reflecting residual activity of factor VIII bound to the patient's antibodies. The ristocetin cofactor activity of normal plasma was unaffected by the antibodies. Transfusion of factor VIII concentrate to the patient resulted in therapeutic levels of circulating factor VIII and transfused factor VIII circulated longer than usual. Partial remission of the disease with adequate levels of VIII:C occurred after 3 months.

Aged↗
PubMed1982

Demonstration of non-idiotypic variable heavy chain (VH) antigens on human peripheral blood lymphocytes.

In this study we have obtained evidence for the expression of Vh-like determinants on unstimulated human T lymphocytes as well as T lymphoblasts. These determinants were detected with antisera raised against isolated VH fragments of a human IgG3 cryoglobulin (KUP). The antisera detect idiotypic, VH subgroup and HV framework determinants and behave as anti-immunoglobulin antibodies when tested against peripheral blood mononuclear cells in immunofluorescence experiments. However, sensitive radiolabelling and immunoprecipitation techniques revealed a certain reactivity against highly purified T lymphocytes. The specificity of these T-cell-reactive antibodies has not been fully established, but the results suggest that the antisera contain antibodies directed at VH fragment-specific antigens or antigens not exposed on native immunoglobulins or isolated heavy chains.

Cell Separation↗
PubMed1982

Anti-VH antibodies interfere with antigen binding by human T lymphocytes.

The effect of antisera against a VH fragment have been investigated in several T cell proliferative assay systems. Anti-VH antisera raised in sheep, rabbits and chicken induced profound inhibition of PPD stimulated lymphoproliferation. Likewise were both mixed lymphocyte reaction (MLR) and autologous mixed lymphocyte reaction (AMLR) severely hampered while stimulation induced by mitogens was only minimally affected. Specificity testing indicates that the inhibiting antibodies in these experiments are not directed against native immunoglobulin determinants but rather against determinants specific for the VH fragment. These results thus support the notion that T cells express VH antigens and that these antigens are part of or closely associated with the antigen receptor on human T lymphocytes.

Antibodies, Anti-Idiotypic↗
PubMed1982

Sheep, rabbit and chicken antisera against a human VH fragment: reactivity with immunoglobulins and lymphocytes.

Antisera against a human VH fragment obtained from an IgG3, VH II, kappa protein (KUP) were raised in rabbits, sheep and chicken. The three types of anti-VH antisera reacted equally well with both intact immunoglobulin molecules and isolated heavy chains. The antisera did not detect any free heavy chain specific antigens by sensitive enzyme-linked immunosorbent assay (ELISA) tests although they reacted with some antigens which were more or less hidden on intact immunoglobulin molecules but well expressed on isolated heavy chains. The antisera reacted with more than 90% of IgG, IgA and IgM present in normal pooled serum. Experiments with T cells from normal peripheral blood indicated that the sheep and rabbit anti-VH antisera reacted with a 70,000 mol.wt T-cell surface antigen.

Animals↗
PubMed1982

Characterization of the mitogenic and antigenic stimulatory properties of a purified streptolysin O preparation.

In vitro transformation of human peripheral blood lymphocytes was induced by a purified group A streptococcal extract rich in streptolysin O (SLO). The stimulation was shown to be largely a general mitogenic effect rather than antigen-selective as a large panel of normal blood donors responded strongly. Further support for a non-specific stimulation was obtained by experiments with cord blood lymphocytes. An antigen-specific response could also be detected as culture supernatants from the stimulation experiments contained immunoglobulins with SLO neutralizing properties. In addition, the total response could partly be inhibited by rabbit heteroantisera against HLA-DR-like antigens supporting the above contention. The stimulatory properties were found to reside in the SLO molecule although results may indicate that the determinants provoking the lymphocyte transformation differ from the determinants possessing the haemolytic properties. Peak response was found on days 4-5. Cell fractionation experiments indicated that only T lymphocytes were stimulated although co-operating B cells and/or monocytes were necessary.

Antibodies↗
PubMed1981

A transient monoclonal human IgG1 kappa protein with anti-thyroglobulin activity: lack of cross-idiotypy with polyclonal anti-thyroglobulin antibodies.

A female patient in her early sixties had for a period of at least 4 months a monoclonal IgG1 kappa protein in her serum and at the same time a very high level of anti-thyroglobulin antibodies. Different isolation procedures showed that the M component was responsible for the high anti-thyroglobulin activity. Anti-idiotypic antibodies raised in a rabbit against the monoclonal protein inhibited the M component's anti-thyroglobulin activity, and purified thyroglobulin blocked the reaction between the M component and the anti-idiotypic antiserum. After the M component had disappeared, no cross-idiotypic immunoglobulins could be detected in the patient's serum, nor could the anti-idiotypic antiserum inhibit the residual anti-thyroglobulin activity present in the serum at this time. No reaction could be detected between the antiserum and the anti-thyroglobulin antibodies of sera of other patients. Idiotypic autoantibodies against the M component, which might have caused its disappearance, could not be demonstrated.

Antibody Specificity↗
PubMed1980

Effect of streptolysin O and digitonin on egg lecithin/cholesterol vesicles.

Artificial membrane vesicles (liposomes) have been used to study the lytic mechanism of the bacterial toxin, streptolysin O, compared to that of the well-known plant glycoside, digitonin. Two types of vesicle were prepared: large unilamellar vesicles and multilamellar liposomes. The vesicles were prepared with varying molar ratios of egg lecithin and cholesterol and loaded with the water-soluble spin label, TEMPO-choline chloride. Lysis of the vesicles was registered as release of spin label and monitored by change in the electron spin resonance (ESR) spectrum. In this system digitonin was able to lyse both large unilamellar vesicles and multilamellar liposomes. The effectiveness of lysis increased by increasing the percentage of cholesterol, but even at 0% cholesterol a significant level of lysis was observed by addition of a large enough concentration of digitonin. In contrast, no lysis was detected from multilamellar liposomes after exposure to streptolysin O, even when they consisted of 50 mol% cholesterol. On the other hand, large unilamellar vesicles could be lysed by streptolysin O, provided the cholesterol content was greater than 33%. At 67 mol% cholesterol in the membranes, the degree of lysis was diminished compared to 50%, which appeared to be optimal. This is the first demonstration of liposome lysis by streptolysin O and demonstrates the cholesterol specificity which has previously been shown by inhibition studies.

Cholesterol↗
PubMed1980

Specificity of receptors for IgG on human cytotoxic plaque-forming mononuclear leukocytes. Induction and inhibition of plaque-forming activity.

Intact rabbit IgG antisheep erythrocyte antibodies, and the corresponding F(ab')2 fragments and partially reduced and alkylated IgG were studied for the capacity to induce cytotoxic plaque formation by normal human mononuclear leukocytes in surface monolayers of sheep erythrocytes. The F (ab')2 fragments did not induce plaque formation, whereas partially reduced and alkylated IgG antibodies had a good plaque-inducing capacity compared to untreated IgG anti-SRBC antibodies. The plaque formation was inhibited by human IgG, but not by IgM, IgA, IgD or IgE. Normal and myeloma IgG in aggregated form gave a stronger inhibition than the corresponding proteins. Strong inhibition was observed with IgG1, IgG3, and IgG4, and with IgG2 after aggregation. Both the Fc and pFc' corresponding to the C terminal domain gave a strong inhibition. Thus, the region of the IgG molecule involved in binding to the Fc receptor of the plaque-forming cells appears to be located within the CH3 domain. These observations, therefore, indicate that the plaque-forming cells are of monocytic origin.

Animals↗
PubMed1980

Comparative studies of a monoclonal IgG lambda and two IgE kappa components from an individual patient: evidence for shared idiotypic determinants between the two IgE proteins but not with the IgG lambda protein.

An IgG lambda and two IgE kappa proteins were isolated from the serum of a patient (DB) with anaemia associated with myelofibrosis. Idiotype-specific antisera produced against the three proteins were studied by precipitation in double immunodiffusion and by enzyme-linked immunosorbent assay (ELISA) and indicated that the two IgE kappa components shared idiotypic determinants while the IgG lambda protein did not show any cross-idiotypic reaction. The idiotypic determinants of the three proteins were not present in pooled normal serum, normal IgG, normal IgE or IgE from a patient with multiple myeloma.

Anemia↗