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  • Author or Editor: Eileen L. Thacker x
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Summary

Assays were developed to detect and measure autoantibodies (aa) to thyroglobulin (Tg) and to the thyroid hormones, thyroxine (T4) and triiodothyronine (T3). An elisa to detect aa to Tg was developed, using purified canine Tg as the antigen and goat anti-canine IgG conjugated with alkaline phosphatase as the second antibody. A highly charged agarose electrophoresis assay was used for determination of aa to T4 and T3. Sera from dogs (n = 119) with clinical signs consistent with hypothyroidism were tested for aa to Tg, T4, and T3. Autoantibodies to at least 1 of the 3 thyroid antigens were detected in 58 of the 119 (48.7%) sera tested. Autoantibodies to Tg were detected more frequently in samples with low serum concentrations of thyroid hormones than in samples with normal concentrations. The presence of aa to T4, T3, or both was not significantly associated with low thyroid hormone concentrations, but this lack of association may have been attributable to binding of aa in the measurement of thyroid hormones by radioimmunoassay.

Free access
in American Journal of Veterinary Research

SUMMARY

Fifty serum samples from dogs with clinical signs of hypothyroidism and autoantibodies (aa) to thyroglobulin (Tg), thyroxine, or triiodothyronine were screened for aa to thyroid peroxidase (tpo). Thyroid peroxidase is the antigen against which microsomal aa are formed in human beings with lymphocytic thyroiditis. The tpo was isolated from canine thyroid tissue, using a modification of the procedure for purifying porcine tpo. The enzyme was solubilized from the membrane, using a deoxycholate-trypsin solution, followed by ammonium sulfate precipitation and diethylaminoethyl Sephadex chromatography. Activity of tpo was determined, using an iodide oxidation assay and a guaiacol assay. A monoclonal antibody to canine Tg, coupled to an immunoaffinity column, was used to eliminate the contaminating Tg from the tpo preparation. Using the tpo preparation as an antigen, an elisa was performed on 10 serum samples and immunoblot assays were performed on 50 canine sera. Autoantibodies to tpo were not found in any of the sera. Assays also were performed, using purified porcine and human tpo and evidence of cross-reactivity with canine tpo was not identified. The absence of aa to tpo in dogs suggests a different pathogenesis for autoimmune thyroid disease in dogs than that hypothesized for lymphocytic thyroiditis in human beings.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate immune responses induced by administration of Mycoplasma hyopneumoniae bacterin to pigs.

Animals—60 healthy 7- to 10-day-old cross-bred boars.

Procedure—Pigs were assigned to 1 of 4 pig groups (15 pigs/group): vaccinated, challenged; vaccinated, nonchallenged; nonvaccinated, challenged; nonvaccinated, nonchallenged. Vaccinated pigs received IM injections of a mycoplasma bacterin on days 0 and 14, whereas nonvaccinated pigs received saline (0.9% NaCl) solution. Pigs in the challenged groups were inoculated intratracheally with M hyopneumoniae on day 42. Pigs were euthanatized and necropsied 41, 44, 48, and 70 days after the first vaccination, and proportion of lung surface with pneumonic lesions was determined. Percentage of lymphocyte subpopulations and number of interferon-γ (IFN-γ) secreting lymphocytes in blood and tissues, cytokine and antibody concentrations in bronchoalveolar lavage (BAL) fluid, and serum antibody concentrations were determined.

Results—Vaccination against and infection with M hyopneumoniae induced a local mucosal immune response in the respiratory tract of pigs. Proportion of lung surface with pneumonic lesions in vaccinated challenged pigs was reduced on day 70, compared with nonvaccinated challenged pigs. Vaccination stimulated the production of M hyopneumoniae-specific IFN-γ secreting blood lymphocytes. Tumor necrosis factor-α concentration in BAL fluid on day 70 was increased in nonvaccinated challenged pigs, compared with vaccinated challenged pigs.

Conclusions and Clinical Relevance—Vaccination against M hyopneumoniae induced local, mucosal, humoral, and cellular immune responses. Moreover, vaccination reduced the severity of lung lesions in challenged pigs, suggesting that mucosal antibodies, mediation of the inflammatory response, and cellmediated immune responses are important for control of mycoplasmal pneumonia in pigs. (Am J Vet Res 2000;61:1384–1389)

Full access
in American Journal of Veterinary Research

Summary

Administration of triiodothyronine (liothyronine, 15 μg, q 8 h, for 6 treatments) caused marked decrease in serum concentration of thyroxine (T4) and estimates of free T4 (fT4) concentration in clinically normal cats. A prospective clinical study was done to evaluate the use of this suppression test for diagnosis of hyperthyroidism in cats with clinical signs suggestive of the disease, but lacking high serum concentration of iodothyronines.

Twenty-three cats were confirmed as hyperthyroid on the basis of histologic changes in the thyroid gland or clinical improvement in response to administration of methimazole. Mean ± sd serum concentration of T4 (34.3 ± 12.7 to 31.3 ± 11.5 nmol/L) and estimate of fT4 concentration (26.6 ± 6.4 to 25.6 ± 6.9 pmol/L) did not change after administration of liothyronine to these cats. Twenty-three cats were classified as nonhyperthyroid by histologic confirmation of other disease, abnormal results of other diagnostic tests that strongly supported primary disease other than hyperthyroidism, or spontaneous remission of weight loss without treatment. Mean ± sd serum concentration of T4 (27.9 ± 10.3 to 11.7 ± 6.4 nmol/L) and estimate of fT4 concentration (21.7 ± 5.4 to 10.4 ± 4.4 pmol/L) decreased significantly (P < 0.001) in response to administration of liothyronine.

Discriminant analysis was used to identify variables from iodothyronine assays (eg, absolute concentration of T4 or absolute estimate of fT4 concentration, or changes of T4 or fT4 concentration) that provided the best diagnostic sensitivity and specificity. The endocrine end points that best differentiated hyperthyroid vs nonhyperthyroid cats were the concentration of T4 or estimate of fT4 concentration in serum obtained after liothyronine administration and predictive values ues calculated from postliothyronine serum concentration of T4 or fT4 and percentage decrease of T4 concentration. Difference in diagnostic sensitivity among endocrine end points compared was not apparent. Use of postliothyronine estimate of fT4 concentration alone or as part of a predictive value improved diagnostic specificity for differentiation of hyperthyroid vs non-hyperthyroid cats (P ≤ 0.081).

Results of this study further confirm existence of hyperthyroidism in cats that do not have high serum concentration of iodothyronines. We concluded that the triiodothyronine suppression test is a safe and accurate test for diagnosis of hyperthyroidism in cats with suggestive clinical signs of the disease, but lacking high serum concentration of iodothyronines.

Free access
in Journal of the American Veterinary Medical Association