CCL2 and idiopathic pulmonary fibrosis: In classic fibrotic diseases, such as idiopathic pulmonary fibrosis (IPF), fibroblasts can up-regulate the expressions of IL-6, IL-8, and CCL2, under the stimulation of IL-1β (45); Furthermore, the expression of CCL5 was also up-regulated in response to CCL21 stimulation in primary lung fibroblasts derived from IPF patients (46).