IL-1ra expression in serum and joint tissue in wild-type and E/P-selectin mutant mice. (a) IL-1ra was not significantly elevated in serum from nonimmunized and post-onset CIA E/P-selectin mutant mice compared with serum from wild-type mice. (b) IL-1ra levels were higher in the joints compared with serum of nonimmunized wild-type and E/P-selectin mutant and wild-type mice, but no difference in IL-1ra levels was found in joint homogenates from nonimmunized E/P-selectin mutant and nonimmunized wild-type mice. Values are expressed as mean ± standard error of the mean. *P < 0.05. IL-1ra, IL-1 receptor antagonist; n, number of mice (panel (a) or number of joints (or mice for serum; panel (b); wt, wild-type.