ROITT , DONIACH AND SOLOMON TABLE I Zone electrophoresis of cytotoxic serum

The presence of circulating autoantibodies in patients with Hashimoto's disease suggests that autoimmunity is implicated in the disease process, but the ultimate proof of an autoimmune pathogenesis of thyroiditis and other human diseases must be obtained by demonstrating the autoaggressive action of antibodies or immunologically competent cells on the living tissue in its normal environment. The demonstration by Pulvertaft, Doniach, Roitt and Hudson (1, 2) of a serum factor capable of destroying human thyroid cells in tissue culture is an advance in this direction. This finding has been confirmed and amplified by Irvine (3, 4) and by Goudie and McCallum (5). Further investigations of this phenomenon are reported in the present paper. The cytotoxic factor is shown to be an antibody reacting with the thyroid microsomal antigen; its mode of action has been further studied and its incidence determined in a variety of thyroid conditions and in persons without overt thyroid disease.