Positive correlation between GP-induced IL-8 and IL-1RA productions. Following stimulation with GP (24 h), we observed a positive correlation between IL-8 and IL-1RA. Moreover, we found this correlation to be dose-dependent, since 100 μg of GP induced larger amounts of IL-8 and IL-1RA than 1 μg GP (n = 5, p ≤ 0.002, r = 0.9 and 0.98, respectively).