IL1B and rheumatoid arthritis: The observation that IL-1 up-regulates the production of PH-20 by both chondrocytes and synoviocytes is worth noting, because enhanced expression of the enzyme may contribute to the degradation of cartilage matrix in arthritides such as rheumatoid arthritis; this contention is strengthened by the observation that proinflammatory cytokines increase the loss of HA fragments from cartilage explants [14].