We crossed TNFα-overexpressing mice, which develop a chronic inflammatory, erosive arthritis similar to rheumatoid arthritis [29], with FAKf/f mice, in which the fak gene is floxed [30], and Rosa26-CreERT2 mice [31], in which Cre recombinase deletes floxed genes upon exposure to tamoxifen. Here, PTK2 is linked to rheumatoid arthritis.