Any alterations in the levels of immune cells in peripheral blood could be hypothesized to have a significant impact on a number of changes described in COPD, including the following (Figure 8): (a) persistence of inflammation (due to elevated levels of MCP-1 and CD8+ T cells), (b) increased susceptibility to viral infections (due to decrease in CD4+ T cells and pDCs), (c) decreased antigen presentation (due to decrease in cDCs and monocytes), (d) impaired clearance of debris (due to decrease in monocytes), (e) decreased immune tolerance (due to decrease in Tregs and TGFß1). Here, CD4 is linked to viral infectious disease.