Several chemokines, including CC motif chemokine ligand (CCL) 2, CCL18, CXC motif chemokine ligand (CXCL) 8, and CXCL9 are increased in the BAL fluid (BALF) of HP patients and contribute to the development of the cellular infiltrate and granulomas in HP (16–20). This evidence concerns the gene CCL18 and hypersensitivity pneumonitis.