Function: Chemotactic factor that attracts monocytes, lymphocytes, basophils and eosinophils, but not neutrophils. Signals through CCR2B and CCR3 receptors. Plays a role in the accumulation of leukocytes at both sides of allergic and non-allergic inflammation. May be involved in the recruitment of monocytes into the arterial wall during the disease process of atherosclerosis. May play a role in the monocyte attraction in tissues chronically exposed to exogenous pathogens. Tissue specificity: Widely expressed. Found in small intestine, thymus, colon, lung, trachea, stomach and lymph node. Low levels seen in the pulmonary artery smooth muscle cells. Similarity: Belongs to the intercrine beta (chemokine CC) family. PTM: One major form (form long), and two minor forms (short chain and medium chain) are produced by differential signal peptide cleavage. The medium chain is about 30-fold less active than the long chain.