In an attempt to better understand the role that myeloid cell derived SIRT1 plays in the pathogenesis of experimental arthritis, Hah et al. (2014) used the well-characterized mouse model of arthritis in which serum from arthritic K/BxN mice was injected into control or Sirt1flox/flox/lysozymeCre mice. The gene discussed is SIRT1; the disease is Arthritis.