CCL2 and pyelonephritis: In pyelonephritis, proinflammatory cytokines, such as Tumor Necrosis Factor-α (TNF-α), Monocyte Chemoattractant Protein-1 (MCP-1), Interleukin-6 (IL-6), IL-8 and IL-23, play an important role in mounting the immune response [25,26].