Biomedical subjects

P Carayon

Publications and source records attributed to P Carayon.

At least 19 recordsLinked to original sources

PubMed1992

Golgi vacuolization and immunotoxin enhancement by monensin and perhexiline depend on a serum protein. Implications for intracellular trafficking.

Vacuole formation around the Golgi and immunotoxin enhancement induced by low doses of the ionophore monensin were inhibited by 50% human plasma (final concentration), whereas the lysosomal pH increase remained unaffected. Immunotoxin enhancement by the Ca2+ antagonist perhexiline was also inhibited by plasma. The inhibiting factor was present in different species and highly concentration-dependent. After purification on DEAE- and CM-Sepharose it showed a heterogeneous distribution between 45 and 50 kDa, in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, an extreme isoelectric point near 3.5, and binding to wheat germ agglutinin-Sepharose. Maximum inhibition was found in the lower molecular mass fraction of 45 kDa. The 50-kDa fraction, although showing immunological identity reactions, remained almost inactive. The simultaneous inhibition of morphological alterations and the enhancement of immunotoxin activity by the highly enriched protein provides a first direct link between both events. Apart from a role of this serum glycoprotein on in vivo inhibition of immunotoxin enhancement, its ability to maintain normal intracellular trafficking in the presence of blocking agents, such as monensin and perhexiline, suggests a more fundamental role in the regulation of these mechanisms.

Biological Transport↗

PubMed1992

Identification of DNA-replicating lymphocyte subsets using a new method to label the bromo-deoxyuridine incorporated into the DNA.

A flow cytometric procedure measuring the 5-bromo-2-deoxyuridine incorporated into the DNA of cells in S phase was modified to make it compatible with the immunofluorescence labelling of cell surface antigens. The modifications were introduced at the stages of cell fixation and DNA denaturation. Ethanol was replaced by Tween 20-containing paraformaldehyde and hydrochloric acid was used for the denaturation of DNA by bovine pancreatic DNase-I. These two modifications permitted the preservation of immunofluorescence properties and the use of fluorochromes of the phycobiliprotein family such as phycoerythrin and allophycocyanin. This new procedure is suitable for evaluating leucocyte subsets proliferating in vitro following stimulation. As an illustration the immunosuppressive effect of cyclosporin A on PHA stimulated T4-lymphocytes was evaluated.

Bromodeoxyuridine↗

PubMed1992

Tyrosine iodination and iodotyrosyl coupling of the N-terminal thyroid hormone forming site of human thyroglobulin modulate its binding to auto- and monoclonal antibodies.

The present work was aimed at studying the interaction of autoantibodies (aAb) and monoclonal antibodies (mAb) with the N-terminal thyroid hormone forming site of human thyroglobulin (TG). Obtained by CNBr treatment of TG, the peptide (22 kDa) containing the complete major hormonogenic site of human TG was purified in three forms according to the degree of iodination and iodotyrosine coupling: the native, poorly iodinated form (n-22K), the iodinated form containing iodotyrosine but not hormone residues (i-22K) and the form containing thyroid hormone (t-22K). We report that aAb from some patients with autoimmune thyroid diseases showed significant binding to both iodinated 22 kDa forms. Furthermore, a detailed study using mAb evidenced that iodination and coupling induced changes in the antigenicity of the molecule, some occurring without direct implication of iodine or thyroid hormones. The 22 kDa peptide appears as an interesting model to study the antigenic changes induced by the structural modifications in the course of thyroid hormone synthesis. This observation could be relevant to the etiopathogenic process of thyroid autoimmune diseases.

Antibodies, Monoclonal↗

PubMed1992

Immunopurification and characterization of thyroid autoantibodies with dual specificity for thyroglobulin and thyroperoxidase.

The presence of autoantibodies (aAbs) to thyroglobulin (TG) and thyroperoxidase (TPO) in most of the patients with autoimmune thyroid disease is now well documented. Studies of these aAbs suggested that some, termed TGPO aAbs, could interact with both TG and TPO. This hypothesis was investigated using IgG fraction from a pool of 25 patients' sera with high TG and TPO aAb titres. Immunopurification of TG, TPO and TGPO aAbs was carried out by sequential affinity chromatography using a large quantity of highly purified human TG and TPO. TGPO aAbs, obtained absorption-elution of affinity purified TG aAbs onto a TPO column, were found to represent about 20% of the TG reactive aAbs and 0.23% of the total amount of IgG. Purified TGPO aAbs were characterized and compared to specific TG and TPO aAbs. In contrast to TG and TPO aAbs which recognized only their target antigen, TGPO aAbs showed high affinity interactions with both TG and TPO. As compared to TG aAbs, TGPO aAbs displayed similar affinity for native TG and higher affinity for denatured TG. Compared to TPO aAbs, TGPO aAbs showed lower affinity for both native and denatured TPO. TGPO aAbs also differed from specific TG and TPO aAbs with regard to IgG subclass distribution and antigen fine specificities as determined by monoclonal antibody assisted mapping of TG and TPO surface epitopes. Taken together, these data indicate that TGPO aAbs are effectively present in the serum of patients with autoimmune thyroid disease. TGPO aAbs may be considered as a subpopulation of TG aAbs with the unique property to cross-react with TPO. The existence of aAbs cross-reacting with these functionally and antigenically related thyroid molecules could lead to a re-examination of the emergence of thyroid autoimmunity.

Antibody Specificity↗

PubMed1992

[Serum human growth hormone assay. Comparison of six assay kits].

Measurements of human growth hormone (hGH) plasma levels using mono or polyclonal antibodies based on kits are often highly variable depending upon the kit used. We compared six kits commercially available: one based on polyclonal antiserum, five based on monoclonal antisera. We measured 695 sera obtained in short stature children (GH deficiency or normal GH secretory) and adults (normal, hypopituitarism or acromegaly). Our results confirm the variability between the assays. The maximal variation was obtained with SBhGH kit which showed mean results 1.7 fold higher than those obtained with hGH Coatria. Using the OMS 80.205 standard with the six kits, we found a good correlation between the six kits indicating that the standard used in each case was not responsible for the observed variations. This suggest that the different antibodies used in these kits may recognize different isoforms of circulating hGH. In addition variations in reagents used in the different kits may also explain these discrepancies. The variations observed using these six commercially available kits may have important clinical repercussion and especially may impede the diagnosis in hGH deficiency in children.

Adolescent↗

PubMed1992

Different concentrations of thyroid peroxidase and thyroglobulin in the nuclear envelope and the endoplasmic reticulum throughout the cytoplasm.

Thyroid peroxidase (TPO) and thyroglobulin (TG) represent two major glycoproteins of thyroid follicular cells performing biological functions such as iodination, transcytosis of thyroglobulin, and formation of thyroid hormones. They are involved in thyroid autoimmunity and thyroid inborn metabolic disorders. Studying these processes at a molecular level includes the determination of their precise intracellular distribution. An evaluation of the relative concentrations of TG and TPO in different subcellular compartments was carried out in stimulated human follicular cells using thin-frozen sections and the immunogold technique. It is documented that TG is transported from the endoplasmic reticulum and the Golgi apparatus to the follicular lumen by transport vesicles; most of it being present in the expanded endoplasmic reticulum throughout the cytoplasm. On the other hand, gold particles indicating TPO are adjacent to the membranes of the exocytotic pathway. They do not label the basolateral membrane but show the strongest density in the nuclear envelope and the apical membrane. The labeling density of TPO is about four times higher in the nuclear envelope than in the endoplasmic reticulum throughout the cytoplasm. In contrast, TG is concentrated three times higher in the rough endoplasmic reticulum throughout the cytoplasm than in the nuclear cisternae. Our results give the first quantitative evidence that TPO and TG are concentrated in different subcompartments of the endoplasmic reticulum. Because previous studies demonstrated the nuclear envelope as the site where the synthesis of endogenous peroxidase (Brökelmann, J., D. W. Fawcett, Biol. Reprod. 1, 59-71 (1969)) begins, we suggest that synthesis of these functionally related proteins happens in specialized parts of the endoplasmic reticulum.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport↗

PubMed1991

Immunohistochemical study of thyroid peroxidase in normal, hyperplastic, and neoplastic human thyroid tissues.

An immunohistochemical study using two monoclonal antibodies (MoAb 30 and MoAb 47) against thyroid peroxidase (TPO) was performed on surgical specimens of human thyroid carcinoma (n = 65), adenoma (n = 70) and Graves' disease (n = 10). Normal adjacent thyroid tissue was used as positive control. Monoclonal antibody 30 reacted significantly with all adenoma and most carcinoma, whereas MoAb 47 reacted with 66 adenoma but only two carcinoma. Of the four adenomas that did not react with MoAb 47, three were of the fetal type. Both carcinoma reacting with MoAb 47 were of the well-differentiated follicular type. These findings further confirm the hypothesis that thyroid carcinoma is associated with changes in the quantity and antigenic properties of TPO. Although the alterations in antigenic behavior revealed by MoAb 47 are not 100% specific, they may allow more accurate diagnosis of malignancy in thyroid tumors.

Adenocarcinoma↗

PubMed1991

Simultaneous identification of eight leucocyte subsets of human peripheral blood using three-colour immunofluorescence flow cytometric analysis.

The full analytical potential of flow cytometry has been exploited in order to identify a maximum of human peripheral blood leucocyte subsets in a single tube. For this purpose a mixture composed of six different monoclonal antibodies directly coupled to FITC or phycoerythrin or indirectly linked to the DuoChrome reagent via the biotin/streptavidin system was used. This combination of monoclonal antibodies and fluorochromes offered the possibility of simultaneously determining eight leucocyte subsets of human peripheral blood using a single laser beam. These subsets were T4 cells, bright and dim T8 cells, T null (CD3+ CD4- CD8-) cells, NK cells and B cells, polymorphonuclear cells and monocytes. This method is very easy to perform, can be applied to samples from other lymphoid tissues such as tonsils and is particularly useful when starting with a low number of cells.

Antigens, CD↗

PubMed1991

Studies of CD4+ (helper/inducer) T lymphocytes in autoimmune thyroid disease: demonstration of specific induction in response to thyroid peroxidase (TPO) in vitro and its relationship with thyroid status in vivo.

We have studied by flow cytometric analysis the antigen specific activation of CD4+ (helper/inducer) T lymphocytes by purified human thyroid peroxidase (TPO). Peripheral blood mononuclear cells were obtained from 26 patients with Graves' disease (GD), 16 with Hashimoto's thyroiditis (HT), 7 with nontoxic nodular goiter (NG), and 14 normal subjects (N). Cells were cultured for 7 days in the presence or absence of TPO at final concentrations of 3, 30, and 300 ng/mL. When harvested, cells were reacted with an FITC-conjugated anti-CD4 and a PE-conjugated anti-HLA-DR murine monoclonal antibodies. The percentage of HLA-DR+ CD4+ cells (activated CD4+ cells) was determined by a flow cytometer. In the absence of TPO, CD4+ cells had been activated without any specific stimulant. This is known as the autologous mixed lymphocyte reaction (AMLR). In the AMLR, CD4+ cells from GD and HT were less activated compared to those from NG and N. Results of TPO-specific activation were expressed as an incremental increase of activated CD4+ cells (II) (percentage of activated CD4+ cells cultured with TPO minus percentage of activated CD4+ cells cultured without TPO). II of N, GD, HT, and NG were 0.37 +/- 0.21, 2.20 +/- 0.45,** 2.0 +/- 0.66,* and 0.35 +/- 0.27 (mean +/- SEM), respectively (**p less than 0.01; *p less than 0.05 vs N). When patients were further subdivided, the highest mean II was found in patients with hyperthyroid GD (p less than 0.01), followed by euthyroid HT (p less than 0.05) and euthyroid GD (p less than 0.05), however there was no significant difference between hypothyroid HT and N. In conclusion (1) AMLR reactivity of CD4+ cells from GD and HT was impaired, (2) however, CD4+ cells from both GD and HT were significantly more induced by TPO compared to N, and (3) this induction depends, in part, on the in vivo thyroid status.

Adolescent↗

PubMed1991

Monoclonal antiidiotypic antibodies interact with the 93 kilodalton thyrotropin receptor and exhibit heterogeneous biological activities.

Ten antiidiotypic monoclonal antibodies (AI mAb) reacting with the TSH receptor were produced by immunization of mice with a mouse mAb directed to a TSH epitope involved in the binding of the hormone to the receptor. The AI mAb were tested for their effects on the TSH receptor-adenylate cyclase system. Four AI mAb behave as agonists of TSH as they compete with TSH for binding to the receptor and stimulate the adenylate cyclase activity. Five AI mAb inhibited both TSH binding to the receptor and adenylate cyclase activity in the presence and absence of TSH; they were thus considered as antagonists of the hormone. One mAb inhibited only slightly the binding of TSH to the receptor and did not interfere significantly with the adenylate cyclase activity. The 10 AI mAb bound with various apparent affinities to solubilized thyroid membrane proteins but not to kidney, spleen, and liver membranes. Membrane desialylation did not significantly alter the binding of the AI mAb whereas deglycosylation modified more or less strongly the binding of mAb to thyroid membranes. It was also shown that the binding to solubilized thyroid membranes of the 10 mAb was inhibited by anti-TSH receptor autoantibodies present in patients with autoimmune disease. The mAb were further analyzed by Western blot analysis. One mAb did not react with the antigen, which suggested that it was directed to a conformational epitope. The other 9 mAb reacted with a protein of 70 kilodaltons and 5 revealed another band of 93 kilodaltons in accordance with the TSH receptor size deduced from the recently molecular cloning.

Adenylyl Cyclases↗

PubMed1991

Determination at the molecular level of a B-cell epitope on thyroid peroxidase likely to be associated with autoimmune thyroid disease.

In a panel of 13 mouse monoclonal antibodies generated against native (nondenatured) human thyroid peroxidase (TPO), only 1 (monoclonal antibody 47) recognized TPO protein fragments expressed in a human TPO cDNA sublibrary. Determination of the nucleotide sequences of 18 clones recognized by monoclonal antibody 47 localized its epitope to 9 amino acids (residues 713-721) in the human TPO protein. On Western blot analysis, only TPO monoclonal antibody 47 recognized the 933-amino acid TPO molecule after denaturation and reduction of the latter, supporting the concept that the major part of the epitope is represented by a continuous portion of the TPO sequence. The binding of TPO monoclonal antibody 47 to native TPO is inhibited by immunoglobulin G in the serum of patients with autoimmune thyroid disease. The epitope for monoclonal antibody 47 defined in the present study is, therefore, part of or in the vicinity of an epitope for autoimmune thyroid disease-associated TPO antibodies.

Amino Acid Sequence↗

PubMed1991

Cigarette smoking and the risk of colorectal adenoma in men.

We evaluated the effect of smoking on the risk of developing colorectal adenoma in men. The data were obtained in a case-control study of 103 men with colorectal biopsy-proven adenoma (cases) and 108 men with normal colonoscopy findings (controls). As compared with men who had never smoked, the estimated relative risk of adenoma increased with the pack-year smoking number, the average number of cigarettes per day, and the total years smoked. The estimated overall relative risk was 2.2 (95% confidence interval, 1.1 to 4.3). Adjustment for age did not alter these results. The data suggest that smokers may have a higher risk of developing colorectal adenoma than non-smokers. If these results are confirmed, they might be of direct importance for public health, since adenomas are precursors of colorectal cancer.

Adenoma↗

PubMed1991

Prevalence of autoantibodies to thyroperoxidase in patients with various thyroid and autoimmune diseases.

An original radioimmunoassay for quantitation of circulating autoantibodies (aAb) to thyroperoxidase (TPO) proved to be well suited for large scale routine testing. The present study was aimed to assess the prevalence of aAb to TPO in patients with various thyroid and autoimmune disease and, for comparison, in women referred for reproductive disorders and indication of in vitro fertilization. Anti-TPO aAb were measured in sera from 32 healthy subjects and 262 patients thoroughly investigated for thyroid dysfunction. As determined in healthy subjects, the normal level of aAb to TPO in serum ranged from 0.30 to 3.07 mg/l (of affinity-purified) anti-TPO aAb. Anti-TPO and anti-MIC aAb levels were both normal in 115 patients and correlated well (r = 0.835, P less than 0.001) in the remaining 147 patients. Coexistence of normal level of anti-TPO aAb and abnormal level of anti-MIC aAb was found in 4 patients and ascribed to a lack of specificity or sensitivity of the test for anti-MIC aAb. Coexistence of abnormal level of anti-TPO aAb and normal level of anti-MIC aAb was found in 67 patients of whom 62 presented only slightly elevated (3.1 to 10.0 mg/l) anti-TPO aAb concentration; the 5 remaining patients, all with overt thyroid autoimmune disease, showed anti-TPO levels between 10.7 to 100.7 mg/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

Induction and increase of HLA-DR antigen expression by immune interferon on ML-3 cell line enhances the anti-HLA-DR immunotoxin activity.

In order to evaluate the impact of induction and increase target antigen expression on immunotoxin potency, we measured the potentiating effect of recombinant immune interferon-gamma (rIFN-gamma) on the cytotoxicity of an anti HLA-DR ricin A-chain immunotoxin (2G5 RTA-IT) on the myeloid cell line ML-3. After 48 h of incubation with rIFN-gamma (500 U/ml) the percentage of 2G5-positive cells increased from 40% to 79%, and the 2G5 mean density was enhanced by 10-fold (11,000 versus 110,000 molecules/cell). Concurrently, rIFN-gamma pretreatment induced a dramatic improvement of 2G5 RTA-IT dose-effect cytotoxicity, as well as immunotoxin cytotoxicity kinetics. When 2G5 RTA-IT was used at the optimal dose of 10(-8)M (the maximum dose which avoided non-specific ricin A-chain cytotoxicity), the immunotoxin-induced cell kill increased with the percentage of DR-positive ML-3 cells according to a similar linear-logarithmic function of rIFN-gamma concentration. Moreover, in the same range of rIFN-gamma concentrations, the killing values and the percentage of DR-positive ML-3 cells were similar if not identical. These findings imply that the enhancement of 2G5 RTA-IT cytotoxicity by rIFN-gamma is mainly related to the rIFN-gamma 2G5 antigen induction on HLA-DR negative cells when immunotoxin was used at 10(-8) M. Furthermore, 2G5 RTA-IT dose-effect cytotoxicity on DR-expressing ML-3 cells, when used at lower concentrations, was also increased by rIFN-gamma in a dose-dependent manner. This result suggests that for immunotoxin concentrations close to the limiting membrane saturation dose (10(-10)M), rIFN-gamma may not solely act by inducing HLA-DR expression on DR-negative ML-3 subpopulation but also by increasing individual cellular DR density on DR expressing ML-3 cells. Finally, our study showed that immunotoxin potency on malignant cell populations which display an heterogeneous antigen expression, could be greatly improved by the use of rIFN-gamma.

Antibodies, Monoclonal↗

PubMed1989

Regulation of thyroperoxidase, thyroglobulin and iodide levels in sheep thyroid cells by TSH, tumor promoters and epidermal growth factor.

Using sheep thyroid cells in culture, we have studied the effects of thyroid stimulating hormone (TSH), epidermal growth factor (EGF) and the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA) on the activity and expression of both thyroglobulin (Tg) and thyroid peroxidase (TPO) and on the ability of cells to trap and organify iodide. Using Western blotting techniques, we found that TSH increased the absolute cellular levels of Tg. The optimum TSH concentration for Tg mRNA production was between 0.1-1.0 mU/ml. Thyroglobulin mRNA levels were stimulated by TSH but detectable levels were also present in cultures grown in its absence containing cortisol, insulin, transferrin, somatostatin and glycyl-lysyl-histidyl acetate. Unlike Tg, TPO protein levels were found to be completely dependent upon TSH. A time course of TSH stimulation of TPO mRNA showed increases after 8 h of TSH stimulation, whereas induction of Tg mRNA by TSH was seen at 24 h. Iodide trapping and organification were also TSH-dependent processes, showing maximum activities at 300-500 muU/ml of TSH. The addition of 10 nM TPA caused a biphasic decrease in radiolabeled pertechnetate uptake, with complete inhibition being seen at 14 h. Inhibition of iodide organification occurred more rapidly. TPA and EGF (1 nM) reduced the amount of newly synthesized Tg in TSH-stimulated cells by 50% but the absolute amount of Tg within the cells was not markedly inhibited at these early times.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Relationship between immunological structure and biochemical properties of human thyroid peroxidase.

Although the primary structure of human thyroid peroxidase (hTPO) has been recently deciphered, little is known about its spatial conformation. Such information is of crucial importance in any attempt to relate the structure with the function of hTPO. To probe the antigenic surface of hTPO and to correlate its immunological structure to its biochemical properties, we used 13 monoclonal antibodies (mAb) displaying various affinity for hTPO. Criss-cross experiments showed 7 clusters of reactivity which were interpreted as reflecting 7 epitopes on the surface of the hTPO molecule. Extending our analysis to partial and nonsymmetrical cross-reactivities, these epitopes were shown to be localized in 4 antigenic domains of the hTPO. We further investigated the nature of these 7 hTPO epitopes by testing mAb binding to peroxidases from various origins and chemically modified hTPO; 3 epitopes were shown to be evolutionary conserved, and 5 resistant to reduction and denaturation. We also analyzed the role of the hTPO epitopes in the enzymatic activity and autoimmune targeting of the molecule. Nine epitopes were shown to be localized at the vicinity of both catalytic sites as the binding of their respective mAb modulated the enzyme activity. Autoantibodies from patients presenting with autoimmune thyroid disorders were essentially directed to epitopes similar or adjacent to those recognized by 8 of the 13 mAb and present on only 2 antigenic domains of hTPO. Taken together these data allowed us to propose a tentative map of the surface of the hTPO molecule which associates its epitopic structure with its biochemical functions.

Antibodies, Monoclonal↗

PubMed1989

Cytotoxic assay of circulating thyroid peroxidase antibodies.

This study describes an assay for the detection of cytotoxicity for thyroid cells in serum of patients with autoimmune thyroiditis. Quantitative measurement may be performed by DNA or [3H] leucine incorporation determinations. The cytotoxic effect is localized in the gamma-globulin fraction, and is complement-mediated. It is thyroid specific i.e. it is not observed with fibroblasts and patients with other autoimmune diseases (patients with lupus erythematosis or glomerulonephritis) do not have cytotoxic antibodies directed against thyroid cells. The thyroid cytotoxicity is related to the presence of antimicrosomal antibodies and the effect of circulating antibodies is inhibited by human thyroid peroxidase. These results strengthen the possible implication of circulating antithyroid peroxidase antibodies in thyroid damage observed in autoimmune thyroiditis.

Animals↗

PubMed1989

Immunocytochemical study of localization and traffic of thyroid peroxidase/microsomal antigen.

We studied the distribution of binding sites for anti-peroxidase monoclonal antibody and anti-microsomal antibodies on isolated human thyroid follicles and a human thyroid cell line. Both open follicles and cells were incubated first with antibodies at +4 degrees C, then with colloidal gold labelled protein A. The topography of the binding sites for monoclonal anti-peroxidase antibody corresponded closely to the expected cell surface distribution of endogenous thyroid peroxidase since labelling was observed at the apical cell surface of the follicles. Furthermore, labelling was restricted to the microvilli level; while smooth membrane territories were devoid of binding sites. In some cases, incubations at 4 degrees C were followed by warming the follicles and cells up to 37 degrees C for 20 minutes in order to study internalization of ligands. Ligands were then observed in intracellular organelles: endosomes and lysosomes. Essentially the same results were observed when human antibodies to the microsomal antigen were used. Controls with microsomal antibodies depleted in anti-peroxidase were negative. In conclusion these findings show that: 1) thyroid peroxidase is present in limited areas on the apical cell surface, 2) labelling of follicles and cells by the anti-microsomal antibodies had the same pattern of distribution as the monoclonal anti-peroxidase antibody, thus suggesting that they recognize the same apical antigens, and 3) TPO/MIC antigen traffics from the cell surface towards lysosomes when the cells are incubated at 37 degrees C.

Autoantigens↗