In our studies we observed maximal MMP-13 production (mean ± SEM) in RA FLS 24 hours after stimulation with IL-1β (1.0 ± 0.3 ng/ml); which plateaued between 48 and 72 hours (0.8 ± 0.3 ng/ml). The gene discussed is IL1B; the disease is rheumatoid arthritis.