As seen in Figure 5, A and B and Supplemental Figure 8, A and B, intraarticular injection of SAA (5 μg/mL) markedly exacerbated the severity of IL-1β–induced arthritis, as assessed by inflammatory cell infiltration (e.g., macrophage infiltration), synovial hyperplasia, and cartilage loss. This evidence concerns the gene SAA2 and Arthritis.