CCL13 and rheumatoid arthritis: CC-chemokines are expressed in RA synovial endothelial cells (ECs) in different concentrations (high-abundance: CCL7, CCL8, CCL14, CCL16, CCL19, and CCL22; low-abundance: CCL1-3, CCL5, CCL10, CCL11, CCL12, CCL13, CCL15, CCL17, CCL18, CCL20, CCL21, CCL23, CCL24, CCL25, CCL26, CCL27, and CCL28 (107), whereas ELR+ CXC-chemokines (CXCL1, CXCL2, CXCL3, CXCL5, and CXCL6) are expressed in the SFs of patients with RA (108).