THE EFFECT OF SOLUBLE COMPLEMENT RECEPTOR-I (SCR1) AND HUMAN THYROID ANTIBODIES ON THE COURSE OF EXPERIMENTAL AUTOIMMUNE-THYROIDITIS IN RATS

Experimental autoimmune thyroiditis (EAT), induced by immunisation of rats with thyroid extract and complete Freund's adjuvant, has been use d as a model to study the effects of complement inhibition mediated by soluble complement receptor 1 (sCR1) administration during the initia l phase of the disease. There was no effect of sCR1 on the severity of thyroiditis at day 28 after immunisation or on the levels of thyroid antibodies, whether sCR1 was given during the first or second week aft er immunisation. Human IgG containing high levels of thyroid peroxidas e antibodies given to rats at the time of immunisation caused signific ant worsening of thyroiditis severity (P < 0.01 compared to animals re ceiving normal IgG) but sCR1 again had no effect in this variant of th e EAT model. The results indicate that complement does not play a majo r role in the initial phase of tissue injury in EAT and complement inh ibition does not impair the generation of an autoimmune response again st the thyroid, although it remains possible that complement activatio n is important during the chronic phase of disease maintenance in huma n autoimmune thyroid disease.