Various mice strains display different susceptibility to development of arthritis and C57/BL6 mice, which represent the predominant mouse strain used for targeted gene disruption, has a lower arthritis response to collagen immunization compared to for instance DBA/121.This difference in disease severity between mouse strains of different genetic background has been linked to different MHC class subtypes and the balance between Th1 and Th2 responses20,22,23. Here, HLA-C is linked to arthritic joint disease.