CCL13 and Nasal polyposis: IL-4 also promotes eosinophil migration through increased expression of vascular cell adhesion molecule (VCAM)-1 on human endothelial cells, and through the release the chemokine MCP-4 (CCL13), an important chemoattractant of eosinophils as documented by its production in supernatant of cultured nasal polyp fibroblasts stimulated with Toll-like receptor (TLR) 2, 3, 4 and 5 ligands [10].