Mice expressing the KRN T cell receptor transgene and the MHC class II molecule A(g7) (K/BxN mice) develop severe inflammatory arthritis, and serum from these mice causes similar arthritis in a wide range of mouse strains, owing to pathogenic autoantibodies to glucose-6-phosphate isomerase (GPI). This model has been useful for the investigation of the development of autoimmunity (K/BxN transgenic mice) and particularly of the mechanisms by which anti-GPI autoantibodies induce joint-specific imflammation (serum transfer model). In this chaper, after a summary of findings from this model system, we describe detailed methods for the maintenance of a K/BxN colony, crossing of the relevant TCR and MHC genes to other strain backgrounds, evaluation of KRN transgenic T cells, measurement of anti-GPI antibodies, induction of arthritis by serum transfer, and clinical and histological evaluation of arthritis.