CCL2 and proliferative vitreoretinopathy: A clinical study revealed that MCP-1/CCL2, CXCL10/interferon-γ-inducible protein 10 (IP-10), and stromal-cell-derived factor 1 (SDF-1) may participate in pathogenesis of both proliferative vitreoretinopathy and proliferative DR, as levels are elevated in DR patients [273], while in severe nonproliferative DR patients the levels of CCL5 and SDF-1α are significantly elevated [274].