The past year has seen a spate of research in the use of HLA transgenic mice in the identification of self antigens associated with autoimmunity. Dominant T cell determinants - and, in a few cases, B cell determinants - have been characterized in the context of disease-predisposing HLA DR and DQ genes for at least three prominent and devastating autoimmune diseases: rheumatoid arthritis, multiple sclerosis and insulin-dependent diabetes mellitus.