Biomedical subjects

K Rajki

Publications and source records attributed to K Rajki.

6 recordsLinked to original sources

PubMed1987

Antigen-gelonin conjugates. Preparation and application in experimental myasthenia gravis.

The antigen-specific immune suppression by gelonin-antigen conjugates was tested in two different systems: (i) the horseradish-peroxidase-stimulated T-cell proliferation in vitro and (ii) in vivo with experimental autoimmune myasthenia gravis (EAMG) in the rat. For this, the phytotoxin gelonin, a glycoprotein from Gelonium multiflorum, was purified and linked to the respective antigens. For the in-vitro assay a lymph node cell suspension from rats immunized with horseradish peroxidase was cultured in the presence of this protein and proliferation was measured by [3H]thymidine uptake. In-vitro proliferation was significantly inhibited by adding gelonin-horseradish peroxidase conjugates. The therapeutic effects of antigen-gelonin conjugates were tested in the rat model EAMG. For these experiments rats were immunized with purified nicotinic acetylcholine receptor from electric fish in order to develop EAMG. The success of the immunization was monitored by the change in physical performance tests, the change in anti-acetylcholine receptor antibody titer, and by the change in the number of ionic endplate channels using a novel electrophysiological method. The latter method permits a very accurate assay of functional damage of acetylcholine receptor at the endplate and correlates well with the clinical severity of the disease. Rats were conventionally immunized with acetylcholine receptor from electric fish. After the onset of EAMG as measured by physical performance tests and rise in antibody titer a group of the animals was injected with an acetylcholine receptor-gelonin conjugate and this treatment was repeated seven days later. The loss in functional acetylcholine receptor was significantly smaller in the therapy group than in the untreated EAMG group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Effector mechanisms in myasthenia gravis: end-plate function after passive transfer of IgG, Fab, and F(ab')2 hybrid molecules.

Using the quantitative ionophoresis technique and the mouse passive transfer model of myasthenia gravis, end-plate function was measured in mice transferred with myasthenic IgG, Fab, or F(ab')2 hybrid molecules prepared by recombination of one acetylcholine receptor (AChR) specific Fab and one Fab directed against irrelevant antigen. The Hill coefficient (a measure for the cooperativity between AChR subunits) and the apparent dissociation constant K for the ACh-AChR interaction were essentially unaltered after passive transfer of IgG or IgG fragments. In contrast, myasthenic IgG and Fab, but not control IgG or Fab, markedly reduced the mean number of end-plate channels. A similar effect was observed after passive transfer of F(ab')2 hybrid molecules. These results show that passive transfer of myasthenic IgG or IgG fragments leads to a quantitative reduction of ACh-controlled end-plate channels, whereas the function of the remaining receptors/channels remains unchanged. The results suggest further that cross-linking of AChR by divalent antibody may not be an absolute requirement for the reduction of AChR at the functional neuromuscular synapse.

Animals↗

PubMed1985

Experimental autoimmune myasthenia gravis: can pretreatment with 125I-labeled receptor prevent functional damage at the neuromuscular junction?

Rats were immunized with purified receptor from electric fish to induce experimental autoimmune myasthenia gravis (EAMG). It is implied by the clonal selection theory that antigens react only with receptors on specific immunocompetent cell subpopulations. In an attempt to damage these specific cells with the aid of highly radioactive antigen, one group of rats was pretreated with an additional injection of radiolabeled receptor of high specific activity 3 days before the basic immunization. The success of the immunization was monitored by measuring changes in the following three parameters: antibody titers against nicotinic acetylcholine receptor; number of alpha-bungarotoxin-binding sites at endplates; and number of acetylcholine-operated ionic endplate channels, using quantitative electrophysiologic methods. Conventionally immunized animals showed the classical signs of EAMG: elevated antibody titers against nicotinic acetylcholine receptor and a reduction of the number of alpha-bungarotoxin-binding sites, as well as reduction of the number of acetylcholine-operated ionic channels. The same symptoms were found in animals pretreated with unlabeled receptor and in animals pretreated with radioactive albumin. Animals pretreated with radioactively labeled receptor showed far less reduction of functional nicotinic acetylcholine receptor and only slightly raised antibody titers. This study suggests that preimmunization with radioactive antigen selectively eliminates immunocompetent cells, thus precluding the production of antibodies by a subsequent immunization procedure. The same protective effect cannot be obtained by either preimmunization with unlabeled antigen or by radioactively labeled unspecific antigen.

Animals↗

PubMed1984

Influence of subclass-specific anti-idiotypic antibodies on the kinetics of the immune response to BCG.

The role of anti-idiotypic subclass-specific antibodies was analysed in the regulation of the immune response to BCG in the guinea-pig. The idiotypes to BCG were separated into subclasses and anti-idiotypes were carried out by immunizing with the purified IgG1 and IgG2 anti-idiotypes. The in vivo T cell response was recorded by tuberculin skin testing, and the in vitro response by lymphocyte stimulation testing with tuberculin. A suppressive effect was detected in cases where the animals were preimmunized with anti-idiotypic IgG2 against anti-BCG IgG1. In the B cell response, the anti-BCG IgG1 and IgG2 subclasses were also quantified by a solid-phase radioimmunoassay. There were 10 times more IgG2 antibodies than IgG1 against BCG in the guinea-pig, and this major idiotypic subclass was suppressed by the IgG2 anti-idiotype raised against anti-BCG IgG2. The minor component anti-BCG IgG1 was slightly stimulated by both IgG2 anti-idiotypes.

Animals↗

PubMed1983

Nursing quality assurance: a process, not a tool.

A meaningful quality assurance program comes only with appropriate knowledge, communication, and accountability for all quality assurance functions among nurses at all levels. Describing the implementation of their quality assurance program, these authors tell of their eventual realization that, in fact, they had merely implemented a quality assurance tool that brought the nursing staff little benefit and a lot of grief. Highlighting the identified problems, the factors contributing to the program's failure, and the actions they took to develop and meet appropriate objectives, they detail their later, successful implementation of the concept and the process of quality assurance. Their experience provides readers with food for thought and stimulus for critical evaluations of their own quality assurance programs.

Attitude of Health Personnel↗

PubMed1982

Analysis of the soluble cytoplasmic components of Mycobacteria and Nocardia by crossed immunoelectrofocusing.

Soluble cytoplasmic components of Mycobacterium tuberculosis, strain H 37 Ra, and Washington II, Mycobacterium bovis, strain BCG and Nocardia asteroides were analysed by isoelectric focusing, crossed immunoelectrophoresis, and crossed immunoelectrofocusing. Using con A-affinity chromatography con A-reactive polysaccharides could be separated from the cytoplasmic fraction which improved the focusing effect. The isoelectric focusing patterns of the various mycobacterial strains were similar, however, concentration differences of the respective components might occur. N. asteroides had a different pattern. By crossed immunoelectrofocusing it was shown that most of the bands of the focusing pattern had antigenic character. Con A-reactive polysaccharides were located near to the cathode, and the con A-nonbound antigens occured close to the anode. Cross-reaction between mycobacteria and N. asteroides was remarkable. In crossed-line immunoelectrophoresis four line in N. asteroides antigens were identical with the highest peaks of M. bovis, strain BCG antigens.

Antigens, Bacterial↗