TNF and anemia: In addition to the joint phenotype, we observed signs of systemic inflammation in spondyloarthritic SKG mice, manifesting as pale BM (a sign of anemia), splenomegaly (Fig. 1b), an intestinal increase in expression of inflammatory genes, i.e., Il1, Il6, Il23, and Tnf (Supplementary Fig. 1c), and weight loss (Supplementary Fig. 1a).