CCL2 and granulomatosis with polyangiitis: Proteinase 3 (PR3), which is mainly produced by neutrophils and is the main autoantigen in granulomatosis with polyangiitis, binds also to endothelium and induces CXCL8 (IL-8) and CCL2 (MCP-1) that provide chemotactic signals for neutrophils and monocytes.