Suppression of murine experimental autoimmune thyroiditis by oral administration of porcine thyroglobulin.

Experimental autoimmune thyroiditis (EAT) induced by the transfer of mouse thyroglobulin (MTg)-immunized spleen cells, activated in vitro with MTg, can be suppressed by oral administration of PTg to donor mice prior to immunization. Oral administration of 1 mg PTg five times over a 10-day period before immunization with MTg-LPS resulted in reduced EAT severity in recipient mice compared with recipients of cells from saline-fed immunized donors. MTg- or PTg-specific proliferative responses were not decreased in PTg-fed donors and anti-MTg antibody was not decreased in the donor mice fed 1 mg PTg. However, anti-MTg antibody production was markedly decreased in recipients of cells from PTg-fed donors compared with recipients of control cells. IgG1, IgG2A, and IgG2B anti-MTg antibody responses were all suppressed by PTg feeding suggesting that tolerance may be induced in both Th1 and Th2 cells. The more severe and histologically distinct granulomatous form of EAT was also suppressed by feeding PTg to donor mice. Studies are underway to determine the mechanism of oral tolerance in this model.