The aim of the present study was to evaluate and compare the CII-directed T cell and antibody specificity at different time points in the course of CIA using two mouse strains on the B10 genetic background - B10.Q, expressing Aq MHC class II molecules, and B10.DR4.Ncf1*/*, expressing human rheumatoid arthritis-associated MHC II DR4 molecules (DRA*0101/DRB*0401). This evidence concerns the gene NCF1 and rheumatoid arthritis.