IL1B and Arthritis: Since FLS cells constitutively express and synthesize IL-1β, and IL-1β is a strong inducer of IL-8 by chondrocytes (42), an amplification loop involving FLS and macrophages in the degradation and erosion of cartilage appears in place within the arthritis synovial tissue, with MMP14 (metallo type 1 matrix metalloproteinases) of critical importance (48–50).