Thyroiditis in NOD-H2^h4 mice born and reared in conventional housing and ingesting different doses of iodine

NOD-H2^h4 mice born and reared under specific pathogen free (SPF) conditions develop thyroiditis that is exacerbated when excess iodine (I) is administered through their drinking water. Little information is available about this strain of mice exposed to normal bacterial flora and intercurrent infections prevalent when born and reared under conventional housing conditions (CHC). Thirty male NOD-H2^h4 mice abouti 2 weeks of age, born and raised under CHC, were divided randomly into 6 groups and given iodinated water ranging from 0.0005% to 0.15% and compared to controls. Water intake was stringently monitored. After 3 months of treatment, the mice were sacrificed. Serum was tested for thyroglobulin (Tg) antibody (Ab) and Tg-IgG subclass Ab. Thyroids were examined for lesions and inflammatory cell infiltration. Water intake was similar for all 6 groups despite different iodine concentrations. 20% of controls showed thyroiditis. I-treated groups showed almost 100% thyroiditis even at the lowest dose. Mean lesion scores correlated with the concentration of I ingested. Lesions correlated closely with IgG_2b Tg-specific antibody. Infiltrations were a mixture of CD4, CD8, and B cells. CHC increased incidence of I-induced thyroiditis, in contrast to the reduced diabetogenic response of parental NOD mice housed under CHC.