We compared results from 1- (n = 4), 2.5- (n = 5), and 5-month-old (n = 7) TNF-Tg mice and their WT littermates (n = 4 for 1-, 5 for 2.5-, and 5 for 5-month-old mice) (Fig. 1a) when 1-month-old TNF-Tg mice have normal joints, 2.5-month-old have mild RA, and 5-month-old have severe joint inflammation and bone erosion. Here, TNF is linked to rheumatoid arthritis.