Experimental autoimmune thyroiditis: attempt to correlate disease development with lymphocyte subset changes.

An attempt was made to correlate lymphocyte subset abnormalities with the development of experimental autoimmune thyroiditis (EAIT) in thymectomized and irradiated rats of five inbred strains. The peripheral blood subpopulations were analysed using the fluorescence-activated cell sorter (FACS-IV). A significant lymphopenia with a severe decrease in helper T cells was identified in all the treated rats. In addition, a significant loss of suppressor cytotoxic T cells was found in rats of the most susceptible strain (August) and in the majority of affected individual rats of the other strains. The simple, modified protocol which we used revealed differences in strain susceptibility to EAIT, with 66% of August rats having histological evidence of disease, 50% of Lewis, 44% of Agus, 30% of Hooded Lister and 20% of Wistar, at 5 to 8 months after treatment. Levels of antithyroglobulin antibody, estimated by an ELISA assay, correlated well with the histological results. In all groups, three times as many females as males were affected. Our findings support the view that genetic and immunoregulatory factors are involved in the development of EAIT, with loss of both helper and suppressor cells playing an important role.