TNF and chronic obstructive pulmonary disease: In COPD, inflammatory responses, mediated primarily by NF-κB as well as tumor necrosis factor (TNF) signaling, were aberrantly activated in monocytes (Fig. 3A), as well as some downstream processes, such as negative regulation of apoptosis and leukocyte migration (Fig. 3B), a clear indication that monocytes function as a component of innate immunity.