Development of collagen type II-induced arthritis (CIA) in apolipoprotein E (ApoE) mutant mice; 8–12-week-old B10.RIII.wild-type (WT), B10.RIII.ApoE^+/– and B10.RIII.ApoE^–/– mice were immunized with collagen type II-complete Freund's adjuvant (col II-CFA). (a) Clinical severity of CIA in individual mice 8 weeks after immunization with col II. Bars represent the mean values. (b) Representative radiological images of the front paws from B10.RIII.WT, B10.RIII.ApoE^+/– and B10.RIII.ApoE^–/– mice before and 8 weeks after immunization with col II. (c) Severity score of individual radiological signs, expressed as the mean ± standard deviation (seven to 10 mice/group), 8 weeks after immunization. Bars represent the mean values. Results from (a) to (c) are representative of four independent experiments. Statistical differences are indicated as follows: n.s. = non-significant; *P < 0·05; **P < 0·01; ***P < 0·005.