We then utilized the K/BxN serum transfer arthritis (STA) mouse model to induce rapid and robust arthritis in naïve mice to better understand the interplay between the NF-κB-IL-1Ra macrophages and synovial fibroblasts, a prominent cell population that influences macrophage phenotype in RA [48, 49]. The gene discussed is NFKB1; the disease is arthritic joint disease.