PPBP and rheumatoid arthritis: These chemokines are differentially produced by different immune cells in patients with RA: T cells produce CCL3, CCL4, CCL5, and CXCL13 (93–96); B cells express CXCL9/10 (97); monocytes generate CCL2, CCL18, CCL19, and CX3CL1 (93, 98, 99); macrophages express CCL25, CXCL4, CXCL7, and CX3CL1 (93, 100, 101); dendritic cells (DCs) produce CCL17, CCL18, and CCL19 (102–104); and neutrophils generate CCL3 and CCL18 (103, 105, 106).