IL1B and Arthritis: Interestingly, when a local form of arthritis was induced by injection of methylated bovine serum albumin (mBSA) plus IL-1β (× 3) into mouse joints, expression levels of all 3 isoforms of mSAA were also higher in the liver than in the joints at an earlier stage of arthritis (days 1 and 3) while becoming much lower in the liver at later stages (day 7) (Figure 8C).