Macrophages and neutrophils also release a multitude of cytokines (e.g., TNF-α, IL-1, IL-6, IL-17A), chemokines (CCL2, CCL3, CCL4, CCL17), and growth factors (TGF-β, PDGF, connective tissue growth factor [CTGF]) that amplify the inflammatory response, leading to alveolitis and fibroblast activation [67,68]. Here, CCN2 is linked to hypersensitivity pneumonitis.