When exposed to YKL-40, macrophages from COPD patients produce elevated levels of the pro-inflammatory biomarkers IL-8, MCP-1, MIP-1α, and MMP-9[26], and YKL-40 is secreted from alveolar macrophages when these are stimulated by TNF-α. The gene discussed is CHI3L1; the disease is chronic obstructive pulmonary disease.