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Biomedical subjects

T Michaelsen

Publications and source records attributed to T Michaelsen.

16 recordsLinked to original sources
PubMed1999

The infant rat model adapted to evaluate human sera for protective immunity to group B meningococci.

The infant rat infection model previously developed to evaluate protective ability of passively administered murine antibodies to group B meningococcal (MenB) surface antigens was adapted for human sera. Several challenge doses were tested, aiming at sensitive detection of protection with little interassay variability. Doses of 10(5) and 10(6) colony forming units of strain IH5341 (MenB:15:P1.7,16) injected intraperitoneally gave consistently high levels of bacteremia and meningitis developed in 6 h in 50-100% of the pups. A monoclonal antibody mAb735 to the MenB capsule, injected 1-2 h before bacterial challenge, gave full protection at a dose of 2 microg/pup. Sera from adult volunteers immunized with a MenB outer membrane vesicle vaccine reproducibly reduced bacterial counts in the blood and cerebrospinal fluid, whereas a normal human serum, lacking bactericidal and opsonophagocidal activity, was unprotective.

Adult↗
PubMed1998

Activation of complement by human IgG1 and human IgG3 antibodies against the human leucocyte antigen CD52.

Activation of the complement cascade by immunoglobulin G (IgG) plays a major role in the host defense against pathogens. Using recombinant human antibodies specific for the leucocyte antigen CD52, different allotypes of human IgG1 subclass were compared for their ability to activate human complement. In addition the roles of the different length hinge regions of IgG1 and IgG3 were investigated. It was found that the naturally occurring allotypes G1m(a,z) and G1m(f), and one artificially created isoallotype, G1m(null), did not significantly differ in their overall ability to cause cell lysis. However, some differences in binding of individual components of the classical activation pathway were detected. More of the complement component C1s seemed to be associated with the allotype G1m(f), although this did not result in an overall improvement in lytic potency. In this system the wild-type IgG3 was found to be less effective in complement lysis than IgG1. By shortening the hinge region of IgG3 to resemble that of an IgG1 antibody, increased complement binding was observed compared with that of wild-type IgG3 and the IgG1 allotypes. The overall lytic potency of the antibody was also improved compared with wild type IgG3 and it was also slightly more effective than the IgG1 allotypes.

Antigens, CD↗
PubMed1994

Immunoscintigraphy of bone sarcomas--results in 5 patients.

The feasibility of using the murine monoclonal antibody, TP-1, for clinical immunoscintigraphy was examined in a pilot study involving 5 patients with bone sarcomas. 131I-labelled F(ab')2 antibody fragments were injected in doses of 0.8-1.0 mg (90-130 MBq), and the accumulation of radioactivity was examined by scintigraphy, and assessed by direct measurements on biopsied tumour and normal tissue. One osteosarcoma patient had a primary tumour in the femur, whereas the other 4 had single lung metastases detected by other diagnostic methods. Immunoscintigraphy of the femoral primary was optimally visualised after 22 h. In 2 patients, the method failed to detect lung metastasis, in 1 of the cases possibly related to less than optimal methodological conditions. In 2 other patients, increased accumulation of radioactivity indicated one and three lung tumours, in addition to the single metastasis observed by X-ray and CT scanning, tumours that were later confirmed and removed surgically. The concentration of radioactivity in tumour and normal tissues 44-72 h after antibody injection could be measured in 4 patients. The tumour to blood ratios were in the range of 1.2-4.2, compared to 0.1-0.8 for various normal tissues. The results indicate that immunoscintigraphy with TP-1 antibody fragments have a potential for early detection of lung metastases in patients with bone sarcoma.

Adolescent↗
PubMed1993

Low prevalence of complement deficiencies among patients with meningococcal disease in Norway.

Sera from 98 individuals who had survived meningococcal disease were analysed for classical and alternative pathway haemolytic activity and the complement components C3, C4 and properdin. No complete deficiency was found. However, median properdin concentration was only 86% in the disease group compared with the controls (P < 0.001). Properdin was also significantly lower in serogroup C disease (median 76%) compared with serogroup B disease (median 90%, P = 0.005). Severe properdin deficiency is an established risk factor for meningococcal disease. The present data may indicate that even moderately reduced properdin level can increase the risk of developing meningococcal disease.

Adolescent↗
PubMed1992

B-cell hybridoma as intraperitoneal tumor model: correlation between tumor growth and monoclonal antibody production.

Murine B-cell hybridoma cells producing an immunoglobulin G1 (K13), specific for human immunoglobulin kappa chains were inoculated intraperitoneally in mice. After intraperitoneal injection of 10(6) K13 hybridoma cells, superficial intraperitoneal implants and ascites developed, resulting in death after 10 +/- 3 days (mean +/- SD). An immunoradiometric assay was developed to measure K13 in murine blood, ascites and culture supernatant. The assay utilized polymer beads coated with human immunoglobulin G. The amount K13 bound to the particles was measured with a 125I-labelled monoclonal rat antibody (LO-MG1-13) specific for mouse IgG1. The assay could be used over a wide working range (2-500 micrograms/l). Kinetic studies suggested that about 10(5) secreting cells were required for detection of K13 in blood. After injection of 10(6) cells, K13 was measurable in blood 1 day later in all animals. Nine of 33 mice injected with 10(5) or less cells survived, and initially showed rising K13 blood levels followed by decreasing blood levels. In conclusion, a close relationship was established between i.p. growth of the hybridoma K13 cell line and the MAb blood levels. The basic concepts of this assay can readily be adopted for other clones with the limitation that pure antigen is needed for solid phase extraction of the MAb from mouse blood.

Animals↗
PubMed1991

Shared idiotypic determinant in mono- and polyclonal anti-phospholipid antibodies with lupus anticoagulant activity.

Of 42 purified human myeloma proteins tested, two (IgG3 Her and IgM Mag) were found to possess strong lupus anticoagulant (LA) and anti-cephalin activity, as assessed by a dilute activated partial thromboplastin time (dAPTT) and ELISA test, respectively. For these proteins, we confirmed the observation reported by others that LA activity is present in the antigen-binding (Fab) portion of the immunoglobulin molecule. Rabbit anti-idiotype antibodies against IgG3 Her inhibited the anti-cephalin activity of this protein, suggesting that the anti-cephalin activity of IgG3 Her depends on the hypervariable part of the immunoglobulin and thus most probably is a true antigen-antibody reaction. The anti-Her idiotype antibodies were also able to bind to and inhibit the anti-cephalin activity of IgM Mag. ELISA binding and inhibition experiments showed that the anti-idiotype antiserum contained at least two sets of anti-idiotypes; one set that recognizes a cross-reactive idiotype shared by IgG3 Her and IgM Mag, and another set that seems to be unique to the immunizing protein IgG3 Her. Both sets of anti-idiotype antibodies also bound weakly to polyclonal (patient) IgG, indicating an idiotypic cross reaction.

Antibodies, Anti-Idiotypic↗
PubMed1989

Heterogeneity of degradation of B-cell endocytosed monoclonal antibodies reacting with different sIgM epitopes.

The degradation of a panel of monoclonal antibodies (MoAb) bound to surface IgM (sIgM) was studied in three human Burkitt's lymphoma cell lines. The panel included MoAb that recognize several distinct epitopes associated with the F(c mu)5 domain, the c mu 2 domain and kappa or lambda light chains. The amount of degraded MoAb and the rate of their degradation varied considerably between the various antibodies. Properties of MoAb such as avidity or ability to cross-link sIgM did not significantly influence their degradation. The most consistent correlation between rate of degradation and MoAb used was the location of the epitope recognized by the individual MoAb. Thus, 7 out of 8 anti-light chain MoAb were degraded at a higher rate than 5 out of 5 anti-F(c mu)5 MoAb. One anti-c mu 2 MoAb was degraded at a rate similar to the majority of anti-light chain MoAb. The intracellular transport of an anti-kappa light chain MoAb and an anti-F(c mu)5 MoAb was studied in detail by subcellular fractionation in sucrose gradients. We found that the anti-kappa light chain MoAb was transported more rapidly to lysosomes than the anti-F(c mu)5 MoAb, showing that they were sorted differently intracellularly.

Animals↗
PubMed1984

Transferrin receptor and B-lymphoblast antigen--their relationship to DNA synthesis, histology and survival in B-cell lymphomas.

The reactivity of two monoclonal antibodies identifying antigens related to B-cell activation, B3/25 (the transferrin receptor) and BB-I (the B-lymphoblast-I-antigen), was examined on cell suspensions from 75 cases of monoclonal B-cell lymphomas. The expression of B3/25 antigen was correlated to DNA synthesis as measured by spontaneous 3H-thymidine incorporation (p = 0.0003) and histopathologically high-grade malignancy (p = 0.00003). Furthermore, B3/25 expression was associated with survival since the patients with B3/25-negative tumors survived longer than those with B3/25-positive tumors (p = 0.018). B3/25 expression also defined a larger group of patients with shorter survival than did histopathology alone, 28 cases versus 16 cases, respectively. On the other hand, the BB-I antigen did not reveal an association with DNA synthesis, high-grade malignancy or survival. However, the findings indicated that BB-I may be related to B-cell maturation/differentiation.

Antibodies, Monoclonal↗
PubMed1983

Triggering of monoclonal human lymphoma B cells with antibodies to IgM heavy chains: differences of response obtained with monoclonal as compared to polyclonal antibodies.

A comparative study of human B lymphoma cells activation by monoclonal (murine hybridoma) antibodies to mu heavy chains (Ma-mu) as compared to polyclonal (rabbit) antibodies to mu heavy chains (Ra-mu) has been carried out. Early events related to calmodulin activation such as 86Rb influx and changes in cell volume at 4 h could be induced by Ma-mu. One antibody (AF6) approached Ra-mu with regard to the strength of response obtained. However, Ma-mus including AF6 were deficient in inducing DNA synthesis under conditions where this was achieved with Ra-mu. Studies in one lymphoma, where stimulation of re-expressed surface IgM could be studied, revealed that Ma-mu was deficient in stimulating re-expressed sIgM. These findings raise questions with regard to polyclonal antibody to surface Ig as a model for B cell triggering by antigen and suggest that antigen-induced B cell triggering may be more complex than indicated by previous studies with polyclonal antibody.

Antibodies, Monoclonal↗
PubMed1982

Monoclonal human B lymphoma cells respond to DNA synthesis to anti-immunoglobulins in the presence of the tumour promotor TPA.

Monoclonal human B lymphoma cells were triggered in vitro to DNA synthesis with F(ab')2 fragments of rabbit IgG antibodies specific for different human immunoglobulin (Ig) light and heavy chains. The specificity of the responses corresponded to surface Ig (sIg) present on tumour cells. Anti-mu chain, anti-delta chain, and antibodies to light chains were found to mediate this effect. However, to induce DNA synthesis, the tumour promotor 12-O-tetradecanoyl-phorbol-13-acetate (TPA) was usually required. TPA alone induced cytoplasmic protrusions and increases in cellular volume. These observations should provide new opportunities to study the triggering of B cells with anti-Ig in well-defined cell populations.

Antibodies, Anti-Idiotypic↗
PubMed1981

Further structural and antigenic studies of light-chain amyloid proteins.

The major subunit protein of amyloid fibrils (758) isolated from a patient with systemic amyloidosis and studied by N-terminal amino acid sequence analysis was found to be almost identical to the sequence of a V lambda IV Bence-Jones protein and a previously described A lambda IV amyloid protein. The two A lambda IV amyloid proteins showed strong antigenic cross-reaction, appearing as antigenic identity in double immunodiffusion tests using anti-A lambda IV antiserum raised against one or the other of the two proteins. In addition, another new A lambda V amyloid fibril protein (R.S.) showed strong amino acid sequence homology and antigenic identity in double immunodiffusions with the prototype of the A lambda V subgroup (the AR protein). Finally, 20 primary or myeloma-associated amyloid proteins were characterized using antisera against the AA and several Ig light-chain-derived amyloid proteins.

Amino Acid Sequence↗
PubMed1980

The solution shapes of IgG3 immunoglobulin and its Fch and Fc fragments. A small-angle X-ray scattering study.

A homogeneous IgG3 protein and its corresponding Fch and Fc fragments have been studied in solution using the small-angle X-ray scattering method. The Fch and Fc fragments were produced by short digestion of IgG3 with papain and trypsin. The results indicate that the overall shape of the IgG3 molecule in solution can best be described as an elliptical cylinder with a total length of 29 nm and with a cross-section having the semiaxes 3.8 and 0.9 nm. Thus, the overall shape of IgG3 is considerably different from the Y-shape normally adopted for the IgG1 molecule. The analysis of the data obtained for the Fch and Fc fragments also yields elliptical cylinders with almost the same dimensions of the cross-section but with shorter total lengths, 11.4 and 6.7 nm, respectively. The molecular weights of the IgG3 protein and the Fch and Fc fragments were determined to be 1.8 x 10(5), 0.61 x 10(5), and 0.50 x 10(5), respectively.

Humans↗
PubMed1977

The interaction of immunoglobulin heavy and light chains in the absence of the VH domain.

Recent studies of the micron- and kappa-chains of the first patient (GLI) with micronHCD indicated that the observed defect was the result of the failure of assembly of the intact kappa-chain to the micron-chain, which lacked the VH domain but had the CH1 Cys normally linked to the light chain. To explore the possibility that the VH region is necessary for the formation of the HL disulfide bond, in vitro studies were performed with GLI micron- and kappa-chains and with the CH1 domain and kappa-chain derived from an IgG3 myeloma protein, KUP, which yields separate VH, CH1, and kappa-chains after papain digestion and reduction. The proteins were reduced and allowed to reoxidize, and the combination products were assessed by gel chromatography under dissociating conditions by SDS-PAGE and by immunoprecipitation techniques. The results suggest that, although in vitro covalent and noncovalent combinations are possible between intact light chains and their autologous heavy chains even in the absence of the VH domain, the efficiency is less than that when the intact Fd region is used. Hence, it seems likely that lack of VH alone is not sufficient to explain the failure of assembly observed in muHCD.

Binding Sites, Antibody↗