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Biomedical subjects

M Mack

Publications and source records attributed to M Mack.

99 records · Page 6Linked to original sources
PubMedDate not supplied

Construction and biological activity of a recombinant bispecific single-chain antibody designed for therapy of minimal residual colorectal cancer.

Unlike monoclonal antibodies, clinical application of bispecific antibodies has so far lagged behind because of difficult, low-yield production techniques as well as considerable toxicity attributed to bispecific antibody preparations containing immunoglobulin-Fc parts and anti-CD3 homodimers. These difficulties were overcome by recombinant generation of a bispecific single-chain antibody (bscAb) joining two single-chain Fv fragments via a five-amino-acid glycine-serine linker. The anti-CD3 specificity directed against human T cells was combined with another specificity against the epithelial 17-1A antigen. The following domain arrangement was critical in this individual case to obtain a fully functional bscAb: VL17-1A-VH17-1A-VHCD3-VLCD3. The bscAb was expressed in chinese hamster ovary cells with a yield of 15 mg/l culture supernatant whereas numerous attempts to obtain a functional protein expression in Escherichia coli failed. The low-molecular-mass bispecific construct (60 kDa) could easily be purified by its C-terminal histidine tail. The antigen-binding properties are indistinguishable from those of the corresponding univalent single-chain Fv fragments as shown by enzyme immunoassay and flow cytometry. We could show that the bscAb, which lacks Fc parts and anti-CD3 homodimers is highly cytotoxic for 17-1A positive tumor cells in nanomolar concentrations and in the presence of human T cells. Most remarkable, it does not stimulate T lymphocyte proliferation in the absence of tumor cells and, moreover, does not induce CD25 up-regulation and the secretion of potentially toxic lymphokines such as tumor necrosis factor alpha, interleukin-6 and interferon gamma. Maximal cytotoxicity (51Cr release) was achieved without notable costimulation and was not further enhanced by adding costimulatory signals such as those delivered by anti-CD28 antibodies. CD8+ as well as CD4+ T cell subpopulations were recruited to exert cytotoxicity against tumor cells with different kinetics. CD8+ cells induced high 51Cr release within 4 h while CD4+ cells required a 20-h incubation. The systemic application of the 17-1A/CD3-bscAb could be a major improvement in therapy against disseminated micrometastatic tumor cells. A prospective, randomized clinical trial showing that an anti-17-1A monoclonal antibody could prolong survival of colorectal cancer patients after 5 and 7 years, warrants an assessment of the clinical efficacy of this bscAb exhibiting a 1000-fold higher specific cytotoxicity against tumor cells in vitro.

Animals↗
PubMedDate not supplied

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency: the prevalent mutation G985 (K304E) is subject to a strong founder effect from northwestern Europe.

Medium-chain acyl CoA dehydrogenase (MCAD) deficiency is a potentially fatal inherited defect of fatty acid beta-oxidation. Approximately 90% of the disease-causing alleles in diagnosed patients are due to a single base mutation, an A (adenine) to G (guanine) transition at position 985 of MCAD cDNA (G985). In a limited number of cases it was found that this mutation was always associated with a particular haplotype, defined by three intragenic restriction fragment length polymorphisms, indicating a founder effect [Kølvraa et al.; Hum Genet 1991; 87: 425-429]. In addition, recent studies of American patients and their ancestors suggested the existence of a founder from northern Europe [Yokota et al.; Am J Hum Genet 1991; 49: 1280-1291]. In the present study we document (1) that the G985 heterozygous frequency in the Caucasian population of North Carolina in the USA is 1/84, which is 5- to 10-fold higher than in non-Caucasian Americans; (2) that there exists a 100% association of the G985 mutation in 17 families with MCAD-deficient patients to a certain haplotype, defined by the restriction endonucleases BanII, PstI and TaqI; (3) that MCAD deficiency due to the G985 mutation is more frequent in the Netherlands, Ireland, England, Belgium and Denmark than in other western European countries, and (4) that the frequency distribution of G985 mutation carriers is 1/68-1/101 in newborns in the United Kingdom and Denmark, and 1/333 in Italy. These results support the notion of a founder effect in northwestern Europe.

Acyl-CoA Dehydrogenase↗
PubMedDate not supplied

LIAISON hCG--an automated chemiluminescent immunoassay for the determination of human chorionic gonadotropin (hCG).

An immunoassay utilizing chemiluminescence and paramagnetic particles has been developed for the new fully automated, random access LIAISON immunoanalyzer. The LIAISON hCG assay is a two-site immunolouminometric one-step assay using two highly specific monoclonal antibodies. Total incubation time is only 10 min. A specially designed unique Reagent Integral contains all specific reagents; the on-board stability of these reagents is given over a very long period (> 4 weeks). The assay works with a 2-point calibrated master curve. 30 microliters sample is added to 200 microliters tracer and 20 microliters antibody-coated magnetic particles. After 10 min incubation the particles are separated, washed and the chemiluminescent signal is generated. The time to first result is only 15 min. The assay with a unique extended standard range up to 5,000 ng/ml shows no high dose hook effect up to 500,000 mlU/ml (spiked sera). The assay detects both the intact molecule and the free beta subunit. The cross-reactivity to FSH, LH and TSH is less than 0.1%. Precision (within-run < 3%; between-run < 5%), linearity, recovery and sensitivity (< 0.5 mlU/ml) are excellent. The assay shows a very good correlation to the LIA-mat hCG (r = 0.996). In summary the LIAISON hCG assay together with the new LIAISON immunoanalyzer is a very rapid and accurate method for the quantitative determination of hCG/beta-hCG in serum.

Antibodies, Monoclonal↗
PubMedDate not supplied

LIAISON Ferritin--an automated chemiluminescent immunoassay for the determination of Ferritin.

An immunoassay utilizing chemiluminescence and paramagnetic particles has been developed for the new fully automated random access LIAISON immunoanalyzer. The LIAISON Ferritin assay is a two-site immunoluminometric one-step assay using two highly specific monoclonal antibodies. A specially designed unique Reagent Integral contains all specific reagents. The cooled reagent compartment guarantees an on-board stability of at least 4 weeks. The assay works with a 2-point calibrated master curve. To perform, the assay, 10 microliters sample is added to 300 microliters tracer and 20 microliters antibody-coated magnetic particles. After 10 min incubation the particles are separated, washed and the chemiluminescent signal is generated. The time to first result is only 15 min. The assay with a unique extended standard range up to 3,000 ng/ml shows no high dose hook effect up to 150,000 ng/ml (spiked sera). The cross-reactivity to human liver ferritin is 100%, to human spleen ferritin 66% and to human heart ferritin 8%. Precision (within-run < 3%; between-run < 5%), linearity, recovery and sensitivity (< 0.2 ng/ml) are excellent. The assay shows a very good correlation to LlA-mat Ferritin (r = 0.994). In summary the LIAISON Ferritin run on the new LIAISON immunoanalyzer and is a very rapid and accurate method rapidly providing reliable results.

Autoanalysis↗
PubMedDate not supplied

Thoracoscopic approach for the pericardium.

The technique of video-assisted thoracic surgery (VATS) offers a new approach for management of effusive diseases of the pericardium. By the thoracoscopic approach, which can be performed through either the right or left chest cavity, an extensive pericardiectomy equivalent to one performed through a thoracotomy can be performed. Patients with benign effusive pericarditis, malignant pericardial effusions with a good prognosis, post-radiation pericarditis, purulent pericarditis, and delayed tamponade after open cardiac procedures can be optimally managed by video-assisted techniques.

Equipment Design↗