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Biomedical subjects

A Gardas

Publications and source records attributed to A Gardas.

At least 37 records · Page 2Linked to original sources
PubMed1991

[Determination of antithyroid antibodies by an immunoenzymatic method; an adaptation for expressing results in international units].

Solid phase immunoenzymatic methods (ELISA) have been developed for the determination of antithyroglbulin (ATG), antimicrosomal (AMc) and antimembrane (ATMA) antibodies in blood serum. The results have been expressed in international units (IU). The level of nonspecific reaction was determined on the basis of 30 samples of blood serum obtained from healthy donors. The double standard deviation values amounted to 8 IU for antithyroglobulin antibodies, 17 IU for antimicrosomal antibodies and 53 IU for antimembrane antibodies at the serum dilution of 1:100. The values of double standard deviation obtained for the healthy donors correspond to the borderline between the positive serum samples and those containing no autoantibodies. The level of autoantibodies in patients with autoimmune diseases of the thyroid varied considerably ranging from complete absence to several thousand units per milliliter in single cases. Antithyroglobulin antibodies were determined simultaneously by using the described method and the commercial kit (Walker, Cambridge) and the results obtained by the two methods were compared. A linear correlation with the correlation coefficient r = 0.93, p < 0.001 was obtained. A good but nonlinear correlation was demonstrated with the methods expressing the results in titre values.

Autoantibodies↗
PubMed1990

The effect of dithiotreitol on thyroid peroxidase and microsomal antigen epitopes recognized by auto and monoclonal antibodies.

The effect of disulphide bridges reduction of the microsomal antigen (Mic-Ag) and thyroid peroxidase (TPO) by dithiotreitol (DTT) has been investigated. The reaction of all 67 tested sera from untreated hyperthyroid Graves' and from 22 Hashimoto's patients with high microsomal antibodies (aAb) titer was diminished by 90-95% by DTT, at pH 9.6. The remaining 5-10% of the activity was not destroyed by DTT. The residual Mic-Ag after DTT reduction was able to inhibit the binding of all 45 Graves' and 22 Hashimoto's tested aAb's to the native microsomal antigen by 100% at high concentration. Reaction of affinity purified TPO with two monoclonal antibodies (mAb) were diminished by 80% to 95% by DTT pretreatment, while the reaction of one mAb with TPO was only slightly affected. The reaction of TPO and Mic-Ag with rabbit polyclonal anti-TPO serum (rabbit a TPO) was diminished by 60% by DTT pretreatment. The immunological reactivity of TPO with aAb's was diminished by 65% after DTT pretreatment. The microsomal antigen-aAb's complex was not destroyed by DTT. Results presented in this paper suggest conformational epitope structure of the Mic-Ag recognized by aAb's in patients with thyroid autoimmune disease (AITD).

Animals↗
PubMed1989

[An immunoenzyme method of determining serum levels of anti-microsomal antibodies].

Content of microsomal antigen and thyroid peroxidase activity have been compared in preparations of thyroid microsomal membranes obtained by three different methods following thyroidectomy performed because of Graves' disease or nontoxic goiter. It was demonstrated that the microsomal membrane preparations originating from the thyroid tissue obtained following operation of goiter in Graves' disease are characterized by several times bigger content of microsomal antigen than those obtained after operation of nontoxic goiter. A sensitive ELISA method has been devised for the determination of microsomal autoantibodies in blood serum. The results obtained by this methods were found to be well correlated (r = 0.67) with those obtained with RIA kits manufactured by Serono. The level of antibodies in blood serum was determined in patients with thyroid disorders and the results were compared with those obtained in a group of patients with autoimmune diseases not associated with the thyroid and in healthy blood donors. The occurrence of antimicrosomal autoantibodies was demonstrated in 90.3% of patients with untreated Grave's disease, in 89% of patients with Hashimoto disease, and in 17.7% of patients with toxic goiter. Low titre of antimicrosomal autoantibodies was found in only small percentage of patients with nontoxic goiter (7.7%) and in patients with autoimmune diseases of nonthyroid origin.

Autoantibodies↗
PubMed1988

Coating of proteins to polystyrene ELISA plates in the presence of detergents.

The influence of several detergents on protein coating of polystyrene plates has been investigated. At concentrations equal to or higher than their respective critical micelle concentration (CMC) all detergents prevent attachment of proteins to polystyrene. However, coating of proteins on polystyrene plates can be achieved in the presence of detergents at concentrations 10-100 times lower than their CMC values. There is a strong correlation between the CMC and the detergent concentration inhibiting protein binding to polystyrene by 50%. The rank correlation coefficient for the binding of thyroid plasma membrane antigens was 0.97 (P less than 0.01). The influence of a detergent on the efficiency of protein coating of plastic surfaces also depends to some extent on protein-detergent interactions. Attachment of small hydrophilic proteins such as human IgG is more strongly inhibited by detergents than is the coating of hydrophobic thyroid plasma membrane antigens or thyroglobulin. Some detergents do not interfere with protein attachment to plastics and permit subsequent ELISA assays for hydrophobic, detergent solubilized plasma membrane proteins.

Cell Membrane↗
PubMed1988

The effect of sulphydryl reagents on the human thyroid microsomal antigen.

High sensitivity of the microsomal antigen epitopes recognized by autoantibodies in sera of patients with thyroid autoimmune diseases to disulphide bridge reducing agents have been detected. The shape of the inactivation curve is different for sera obtained from different patients, but for most sera 50% inactivation is obtained below 1 mM of dithioerythritol. The inactivation strongly depends on the pH of the incubation buffer and is most pronounced at alkaline pH (9.6). Cross-linking of the soluble microsomal antigen by glutaraldehyde makes the epitopes resistant to DTE. Binding of the microsomal antigen to polystyrene makes it up to 5 times more resistant to DTE. The microsomal peroxidase enzymatic activity is destroyed by low concentration of dithioerythritol and the inactivation is not dependent on the buffer pH (7.4-9.6). The data demonstrated that the major microsomal antigen epitope is discontinuous (conformation dependent).

Autoantigens↗
PubMed1988

Comparison of autoantibodies level in thyroid autoimmune diseases estimated by different methods.

Autoantibodies to different thyroid cell components in serum of patients with thyroid disease have been estimated by several methods. The TSH receptor antibodies (TRAb) have been detected in 77% of untreated Graves-Basedow, in 70% of thionamide drugs treated Graves-Basedow patients up to four months of the treatment and in 48% of patients with Hashimoto's thyroiditis. Microsomal antibodies (MAb) and thyroid plasma membrane antibodies (ATMA) have been detected in 84% and 68% respectively, in thionamide drugs treated Graves-Basedow and in 91% and 72% in Hashimoto's thyroiditis. The thyroglobulin antibodies have been detected in 42% of untreated Graves-Basedow, in 47% of thionamide drugs treated Graves-Basedow and in 77% of Hashimoto's thyroiditis. In 19% to 21% of patients with toxic nodular goiter underlying autoimmunological process have been established by the detection of high levels of serum autoantibodies (ATMA and MAb). In the non-toxic nodular goiter, non-thyroid autoimmune diseases and healthy blood donors only thyroglobulin antibodies were detected in a significant number of patients. Other types of antibodies (ATMA or MAb) were detected only in sporadic cases of non-thyroid autoimmune diseases.

Autoantibodies↗
PubMed1986

Enzyme-linked immunosorbent assay of autoantibodies reacting with thyroid plasma membrane antigens in sera of patients with autoimmune thyroid diseases.

A sensitive and specific enzyme-linked immunosorbent assay (ELISA) for the detection of autoantibodies reacting with thyroid plasma membrane antigens has been established. Autoantibodies reacting with thyroid plasma membrane antigens were detected by the ELISA in 95% of untreated hyperthyroid Graves', 68% of antithyroid drug-treated Graves' up to four months of the therapy, in 62% of Hashimoto's thyroiditis and in 8.9% of toxic nodular goitre. The ELISA was negative in 100% healthy blood donors, 100% non-toxic nodular goitre, in 12 patients with rheumatoid arthritis, 18 patients with scleroderma and 94% of patients with systemic lupus erythematosus. The mean value of autoantibodies titre was higher in untreated hyperthyroid Graves' (1:84,000) and lowest in positive patients with autoimmune disease of non-thyroid origin (1:4000). The cross-reactivity of antimicrosomal antigen antibodies was below 10%; there was no influence of antithyroglobulin antibodies on the ELISA; and most of the autoantibodies react with plasma membrane antigens different from the TSH binding sites.

Antigens↗
PubMed1985

Measurement of autoantibodies against human eye muscle plasma membranes in Graves' ophthalmopathy.

Antibodies that reacted with plasma membranes of human eye muscle but showed no binding to plasma membranes of human skeletal muscle were identified in serum of patients with Graves' ophthalmopathy. Rabbit antithyroglobulin serum at a dilution of 1 X 10(-3) to 20 X 10(-3) had no effect on the binding of these antibodies to eye muscle membrane antigens. There was no correlation between antihuman eye muscle plasma membrane antibodies and antihuman thyroid membrane antibodies or antibodies against thyroglobulin. It is suggested that specific antibodies against eye muscle membranes are present in Graves' ophthalmopathy and that this disease might represent a distinct autoimmune disorder.

Adult↗
PubMed1984

Simple and sensitive method for estimation of antithyroid plasma membrane antibodies in the serum of patients with autoimmune thyroid diseases; comparison with other assays.

The ability of protein A from Staphylococcus aureus to interact with Fc fragments of IgG was used to estimate the antithyroid plasma membrane antibodies in sera of patients with Graves' disease. The results were expressed as an antithyroid plasma membrane antibodies (ATMA) index. The ATMA index estimated in 60 healthy blood donors varied from 0.57 to 1.28, with a mean value of 0.99, SD theta 0.20. The ATMA index in hyperthyroid untreated Graves' disease varied from 1.80 to 8.0, with a mean value of 4.7. Autoantibody binding to thyroid plasma membranes could be inhibited by (Fab)2 fragments obtained from the serum of patients with Graves' disease but not by (Fab)2 fragments obtained from the serum of healthy blood donors. The influence of rabbit antithyroglobulin and antimicrosomal antibodies on the ATMA index estimation has been evaluated. The ATMA index estimation was compared with the thyrotrophin binding inhibiting immunoglobulins (TBII) index and with the adenyl cyclase stimulating activity of immunoglobulins obtained from 92 hyperthyroid Graves' patients. The ATMA index was positive in 97%, the TBII index in 62% and TSI in 35% of cases. This method using protein A could also be used for estimation of ATMA in other autoimmune thyroid disorders.

Autoantibodies↗
PubMed1984

The presence of autoantibodies directed to thyroid plasma membrane antigens in sera of patients with thyroid disorders, estimated by the reaction with labelled protein A.

The presence of antithyroid plasma membrane antibodies (ATMA) has been detected in 97% of patients with untreated hyperthyroid Graves' disease, 85% of methimazole treated hyperthyroid Graves' disease, 25% of Hashimoto's thyroiditis and 6.9% of patients with toxic nodular goitre. The ATMA index was negative in all healthy blood donors, in patients with non-toxic nodular goitre, with the thyrocardiac syndrome and with simple obesity. Studies of patients with non-thyroid autoimmune diseases revealed that ATMA is positive in 11% of patients with scleroderma, 17.6% of systemic lupus erythematosus and 16% of rheumatoid arthritis. The amount of immunoglobulin bound to thyroid plasma membranes after pre-incubation with serum from patients with Graves' disease varied from 4.2 to 25.2 pmoles per mg of membrane protein; these values are several times higher than the maximal binding capacity for thyrotrophin which is 1.28 pmole/mg protein. In the majority of the cases studied TSH did not significantly inhibit IgG bound from thyroid plasma membranes. Significant amounts of IgG were displaced by an excess of TSH only in three cases with untreated hyperthyroid Graves' disease.

Autoantibodies↗
PubMed1983

Influence of antiganglioside antibodies on thyrotrophin binding and adenyl cyclase activity of thyroid plasma membranes.

Antibovine thyroid ganglioside antibodies developed in rabbits inhibit thyrotrophin binding to human thyroid plasma membranes. These antibodies are specific for gangliosides as was shown by the liposome agglutination technique. Antiganglioside antibodies did not stimulate basal adenyl cyclase activity in bovine thyroid plasma membranes, but most antiganglioside antibodies inhibit the activity of thyrotrophin stimulated adenyl cyclase. Antiganglioside antibodies react well with bovine thyroid plasma membranes and have considerable cross-reactivity with porcine and human thyroid plasma membranes. Rabbits which develop antiganglioside antibodies after some time have detectable levels of autoantithyroglobulin antibodies in their serum although the preparation used for imminisation did not contain any thyroglobulin or protein material.

Adenylyl Cyclases↗