CD80 and autoimmune thyroid disease: Although unclear, the potential mechanisms through which IFN-α might promote the development of thyroid autoimmunity are multiple, including facilitation of antigen presentation through increased expression of the adhesion and costimulatory molecules ICAM-1, B7.1, and MHC class I antigens on thyrocytes, activation of cytotoxic T-cells, promotion of autoantibody production through direct and indirect effects on B-cell and immunoglobulin class switching, upregulation of thyroid specific antigens, and direct toxicity on thyroidal cells (18, 24).