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Biomedical subjects

T Barkas

Publications and source records attributed to T Barkas.

At least 37 records · Page 2Linked to original sources
PubMed1982

Bovine complement: formation of a lytic system between heat-inactivated foetal calf serum and fractions from normal human serum.

Although heat-inactivated foetal calf serum is regularly used as an "inert" additive for culture media, reconstitution of complement activity occurred on the addition of fractions of human sera. The nature of these factors is discussed. Chicken erythrocytes (CRBC), the target cells used in the study, were directly shown to be susceptible to the lytic action of bovine serum, suggesting their potential use in the assay of bovine complement.

Animals↗
PubMed1982

Lack of inter-animal cross-reaction of anti-acetylcholine receptor antibodies at the receptor-binding site as demonstrated by heterologous anti-idiotype antisera: implications for immunotherapy of myasthenia gravis.

Anti-idiotype antisera were raised in rabbits by immunization with purified sheep anti-Torpedo receptor antibodies. The antisera were able specifically to block the binding of receptor to the inducing antibodies but not anti-Torpedo antibodies from other animals of the same, or other, species. Rabbits producing the anti-idiotype sera were not protected from experimental autoimmune myasthenia gravis (EAMG). The implications of these observations for the potential use of anti-idiotype antisera in the treatment of myasthenia gravis are discussed.

Animals↗
PubMed1982

Experimental myasthenia gravis is inhibited by receptor-antireceptor complexes.

Experimental autoimmune myasthenia gravis (EAMG) induced in rabbits by immunisation with purified nicotinic acetylcholine receptor from Torpedo marmorata is a highly reproducible model for the human disease. Pretreatment of experimental animals with immune complexes containing receptor and anti-receptor antibodies suppressed the subsequent induction of EAMG. Animals were protected from the normal severe paralysis. Moreover, antibody levels were reduced by synthesis of antibody rapidly terminated. Possible mechanisms are discussed.

Animals↗
PubMed1982

Circulating immune complexes detected by binding of radiolabelled protein A in patients with oral cancer and oral premalignant lesions.

Circulating immune complexes were determined in 48 patients with oral squamous cell cancer, 17 patients with oral keratosis and 49 controls, using a rapid sensitive assay using a Staphylococcus aureus immunoadsorbent. Concentrations of immune complexes were significantly higher in patients with oral cancer and in patients with oral keratosis than in controls, but the levels in those with oral cancer were not significantly different from those in keratosis. Immune complexes might be responsible for the cell-mediated immune defect in patients with cancer in the head and neck.

Antigen-Antibody Complex↗
PubMed1982

alpha-Bungarotoxin displacing antibody in myasthenia gravis.

The majority of sera from myasthenic patients cannot precipitate all available receptor-toxin complex even in conditions of a 4,000-fold excess of antibody. This effect was traced to displacement of toxin from the receptor-toxin complex. Pure IgG prepared from the serum of a myasthenic patient was as effective as the original serum in displacing ability. The possible effect of such antibodies on the correlation of antibody titre and disease state is discussed.

Antibody Specificity↗
PubMed1981

A simple, rapid and sensitive assay for immune complexes using a Staphylococcus aureus immunoadsorbent.

A simple, rapid and sensitive assay for immune complexes which does not require maintenance of cell lines or purification of proteins is described. The method consists of preferential precipitation of complexed immunoglobulin followed by binding to Staphylococcus aureus and detection by radiolabelled protein A. 3-6 microgram/ml of aggregated IgG can be readily detected in the presence of normal human serum. Soluble in vitro produced complexes can be detected over a very wide range from 4 to more than 100 fold excess of antigen over equivalence. Complexes were found in sera from patients with a range of autoimmune disorders or lung cancer. Fractionation of SLE serum showed the presence of two peaks of complex material of higher molecular weight than IgG. Interference by free immunoglobulin or antibodies to S. aureus has been discounted. Evidence is put forward for the presence of two or more binding sites for protein A on the IgG molecule.

Animals↗
PubMed1981

Immune complexes in myasthenia gravis.

Low levels of circulating immune complexes were detected in 42% of 50 patients with myasthenia gravis. Although a number of these had other associated autoimmune disorders, 30% of patients with no clinical evidence of other disorders were positive in the assays used. The nature of the antigen or antigens in the complexes is not known. However, no binding of alpha-bungarotoxin (a specific probe for the acetylcholine receptor) to the complexes was observed. No correlation of presence of complexes and duration or severity of disease or antibody titres to the acetylcholine receptor was found.

Acetylcholine↗
PubMed1980

Interrelationship of concanavalin-A-binding and antigenic sites on the acetylcholine receptor from Torpedo marmorata.

A preparation of purified 125I-labelled acetylcholine receptor was shown to bind to concanavalin A and to be totally bound by rabbit antiserum to Torpedo acetylcholine receptor. Pre-incubation of the receptor with F(ab')2 and Fab fragments from antibodies against Torpedo acetylcholine receptor, or with corresponding fragments from control immunoglobulin G showed that subsequent binding of the receptor to concanavalin A was specifically inhibited to a maximum of approximately 25% by the immune fragments. Treatment of acetylcholine receptor with periodate or with glycosidases apparently destroyed or removed carbohydrate residues without affecting the antigenicity of the receptor as assessed by radioimmunoassay. These results suggest that although there is a steric interrelatonship between the antigenic and concanavalin-A-binding sites of the receptor the latter sites do not contain its major antigenic determinants.

Acetylcholine↗
PubMed1979

Serum factors influencing antibody-directed cell-mediated cytotoxicity (ADCC) and their effects on the detection of immune complexes by inhibition of ADCC.

An imporved assay system, using inhibition of ADCC, for the detection of 0.6 microgram/ml. of aggregated IgG in medium is described. Under these conditions, normal human serum is extremely inhibitory, this effect being attributed mainly to the weak binding of monomeric IgG. Enhancement of ADCC by albumin was also observed. Using this assay system without further modification, immune complexes may be detected in gel-fractionated sera by the distribution of the inhibitory material relative to the IgG peak. However, for routine use in the assay of untreated sera, a modification of the method is required. Preincubation of the spleen cells with the serum in the presence of EDTA, followed by a washing stage, reduces the background inhibition by normal sera to a low level. Effects of serum factors in producing variable amounts of background inhibition or stimulation are also avoided. The modified assay is sensitive to 6 microgram/ml of aggregated IgG in neat serum.

Animals↗
PubMed1979

Induction of an Fc conformational change by binding of antigen: the generation of protein A-reactive sites in chicken immunoglobulin.

Chicken antibody alone does not bind to Staphylococcus aureus or protein A-Sepharose. Immune complexes containing chicken antibodies do bind, however, showing protein A-binding sites exist on the molecules. Binding does not occur via the antigen contained in the complex. Complexes formed in far antigen excess also bind, suggesting that an induced conformational change in the Fc region of the immunoglobulin occurs but only a fraction of the total chicken antibody is reactive.

Animals↗