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Biomedical subjects

H Isliker

Publications and source records attributed to H Isliker.

At least 37 records · Page 2Linked to original sources
PubMed1981

Antibody-independent interactions between Escherichia coli J5 and human complement components.

With the characterization of an increasing number of molecules that are capable of activating the 1st component of the classical pathway of complement (C), the possibility that some Gram-negative bacteria may activate C1 independent of naturally occurring antibody has been reexamined. We have confirmed a previous report that purified C1 (the activated form of C1) can bind to certain strains of bacteria and it retains its enzymatic activity when thus bound. The availability of purified C1 in its precursor form has allowed us to extend these observations to the native C1 molecule. Using a semirough mutant of Escherichia coli, the galactose epimerase-deficient strain E. coli J5, we have examined the binding and activation of radiolabeled C1. J5 bound radiolabeled C1 in a dose-dependent manner and essentially all of the bound C1 was activated as judged by SDS-PAGE. The bacteria-C1 complex consumed purified C4 and C2 and the consumption of C2 was proportional to the C4 concentration. Subsequent addition of terminal C components C3-9 supplied as serum-EDTA caused a highly significant decrease in bacterial viability. These results demonstrate that C1 may bind to the bacterial membrane in such a manner as to initiate a bactericidal reaction. Therefore, antibody-independent binding and activation of C1 must be considered in the assessment of serum sensitivity of Gram-negative bacteria.

Animals↗
PubMed1979

Inhibition of the interaction between the complement component Clq and immune complexes.

Several groups of compounds were examined for their ability to inhibit in vitro the binding of Clq to insoluble immune complexes. As expected from previous studies, polyinosinic acid, liquoid, sodium pentosan polysulfate, aliphatic diamines and heparin are good inhibitors. This study shows that compounds with much lower toxicity, such as certain amino acids and substances with vitamin B6 activity (pyridoxal-5-phosphate:P5P) were also capable of decreasing the binding of Clq. Using methods of equilibrium dialysis and difference spectra, it was shown that this compound binds to both, Clq und IgG antibody by forming Schiff bases. Clq binds approximately 10 times more P5P when compared to IgG. Immune complexes prepared with IgG antibody modified by P5P and stabilized with sodium borohydride had the same complement-fixing and Clq-binding capacity as normal immune complexes. This suggests that the inhibition of Clq-binding to immune complexes by P5P is due to a modification of lysyl resides in Clq. Collagen and IgG fragments derived from Fc were also found to inhibit Clq binding to immune complexes, but at higher concentrations than the above small-molecular compounds and with a different mode of action.

Animals↗
PubMed1978

Activation of the classical and alternative pathways of complement fixation by immune complexes containing normal and tryptophan-modified immunoglobulin G.

Koshland's reagent (2-hydroxy-5-nitrobenzyl bromide (NBB)) has been shown to modify tryptophanyl residues in anti-ovalbumin IgG. As little as 2 moles NBB/mole IgG antibody are sufficient to block the classical pathway of complement activation when the antibody is complexed to antigen (ovalbumin). In contrast, immune complexes containing antibody with the same degree of tryptophanyl substitution will activate the alternative pathway of complement fixation. Immune complexes containing F(ab')2 fragments derived from anti-ovalbumin IgG do not activate the classical pathway. When measuring the percentage activation of C3 using the method of Laurell, NBB does not affect the alternative pathway of the complement system up to a molar ratio of 2 NBB/F(ab')2. The above findings, provide a means to evaluate the relative contribution of complement activation by the different pathways.

Animals↗
PubMed1977

Immunoglobulins in human cervico-vaginal secretions.

The concentration of IgG, IgA and IgM has been measured in the cervico-vaginal secretions of 8 women with a normal menstrual cycle, 52 pregnant women, 6 post-menopausal women and 12 women with total hysterectomy. No significant difference in immunoglobulin levels was found in the cervico-vaginal secretions of women with a normal cycle as compared to those of post-menopausal or pregnant women. A significant decrease of the IgG/IgA ratio was noticed during ovulation as a consequence of increased IgA secretion. In patients with hysterectomy, the secretions are of vaginal origin only and contain negligible quantities of IgA. Secretory IgA is found essentially in the superior genital tract. IgM is present in trace amounts in all secretions and does not vary considerably. The secretion of immunoglobulins may be under hormonal control: in addition to ovarian hormones, corticosteroids seem also to be involved. The local application of a fluorinated corticosteroid into the vagina has produced a significant decrease of secretory IgA production. The therapeutic possibilities of administering a fluorinated corticosteroid in cases of sterility which are due to the production of anti-spermatozoal antibodies are discussed.

Adult↗
PubMed1977

Proteolysis of bovine immunoglobulins.

Bovine serum IgG1, colostral IgG1 and serum IgG2 with anti-ferritin activity were digested with pepsin or trypsin. Their fragments were characterized by immunoelectrophoresis, gel electrophoresis and gel filtration; their ferritin-binding ability was determined. The kinetics of proteolysis were established by measuring the appearance of free amino groups. No differences were observed between serum and colostrum IgG1. IgG1 was more susceptible to pepsin, and IgG2 to trypsin. This became evident from both the amount of intact IgG determined by gel electrophoresis, immunoelectrophoresis or gel filtration, and from the kinetics of the appearance of amino groups. A model is presented to explain the size, mobilities and properties of the obtained fragments.

Animals↗
PubMed1975

Chemical analysis and electron microscopy studies of human C1q prepared by different methods.

Five differently isolated and purified human C1q preparations were examined by electron microscopy and analyzed by polyacrylamide gel electrophoresis in 0.1% sodium dodecyl sulfate and 0.5 M urea. The amino acid and carbohydrate composition of C1q purified by the DNA method are reported and compared with results obtained on C1q isolated by other procedures. Electron microscopy showed that all C1q preparations had six peripheral subunits connected by fibrillar strands to a central subunit. The presence of small amounts of dimers was also observed. The physico-chemical properties of the molecule are independent of the purification method used. The five C1q preparations labeled with 125I in presence of lactoperoxidase formed two types of noncovalently linked subunits. In each case the smaller (central) subunit contained over thirty times as much radioactivity as the larger (peripheral) subunit supposed to interact with immune complexes. Reduction and alkylation confirmed for each preparation the presence of three polypeptide chains, the smaller of which contained essentially all radioactivity.

Amino Acids↗