The levels of ELR+ CXC chemokines are elevated in the joints of this arthritic mice and neutrophils, which have upregulated CXCR2 in the joint, are the main effector cells, making the K/BxN serum transfer-induced arthritis mice a valid model to test the therapeutic efficacy of our engineered binders13,14,37,38. This evidence concerns the gene CXCR2 and arthritic joint disease.