CCL13 and nasal cavity polyp: One study showed that fibroblasts may be a major source of Th2 chemokines and that TLR2, 3, 4, and 5 ligands can synergistically induce the production of CCL13 in nasal polyp fibroblasts when combined with IL-4, while TLR7/8 or 9 ligands do not induce its production (53).