The development of anti-CII antibody and lipopolysaccharide (LPS)-induced arthritis and tumor necrosis factor-alpha production after LPS challenge in RP105-deficient mice. (a-d) RP105+/+ (n = 9) and RP105-/- (n = 9) mice were injected with a cocktail of monoclonal anti-CII antibodies intravenously and with 50 μg (a, b) or 10 μg (c, d) of LPS intraperitoneally 2 days later. The incidence of arthritis of paws (arthritic paws/total paws) (a, c) and disease severity, expressed as the mean arthritis index (and standard error) of mice (b, d), is shown. Arthritis index was significantly higher in RP105-/- mice with 10 μg of LPS (*P < 0.05 for comparison with RP105+/+ mice, Mann-Whitney U test). (e, f) RP105+/+ and RP105-/- mice were challenged intraperitoneally with 50 μg (e) (n = 10 and 11, respectively) or 10 μg (f) (n = 7 and 9, respectively) of LPS. The serum was collected 1 hour later and the tumor necrosis factor-alpha levels were measured. Values are mean ± standard error. **P < 0.01, Mann-Whitney U test. CII, type II collagen.