Adjuvant-induced arthritis (AIA) model

Female Lewis rats (6–8 weeks; ARC, Perth, Australia) were used in this study based on established protocols (Whiteley and Dalrymple, 2001), as they are the most susceptible strain to the induction of arthritis with heat-killed Mycobacterium tuberculosis. In addition, female rats tend to develop arthritis more readily than male rats, which is similar to what occurs in human rheumatoid arthritis. Animals were housed in standard laboratory cages under control conditions (12-h light-dark cycles, 22°C, 60% humidity) in groups of 4–6, with free access to food and water on tissue and shredded paper bedding. Rats were given a minimum of 7 days to acclimatize to the housing conditions. After this period rats were anesthetized via brief exposure to 2% isoflurane (Abbot, Cronulla, Australia) before receiving a single subcutaneous injection of Complete Freund's Adjuvant (CFA), containing 1 mg heat-killed M. tuberculosis (20 mg/ml) (Chondrex, Washington, USA) into the base of the tail. The experiments were approved by The University of Newcastle Animal Care and Ethics Committee.