Figure 2.

Respiratory anti-viral innate immune response. (A) Activity of natural killer cells. Natural killer (NK) cells are involved in the elimination of virus-infected cells because of their cytotoxic capacities. NK cells are recruited to the lungs early after respiratory virus infection. Dendritic cells (DCs) potentiate NK-cell activation and cytotoxicity. In addition, alveolar macrophages are also required to activate NK cells. (B) Inflammatory response. Epithelial cells and macrophages are crucial in the innate immune response to respiratory virus. Several chemokines and cytokines including IL-8/CXCL8, IP-10/CXCL10, MCP-1/CCL2, MIP-1a/CCL3, MIP-1b/CCL4, RANTES/CCL5, IL-6, TNF, and IL-1 are produced by epithelial cells and macrophages in response to virus infection. Upregulation of these cytokines and leads to recruitment of neutrophils, which constitute the majority of infiltrating cells. While neutrophils may mediate elimination of virus-infected cells, their high numbers, ability to secrete further cytokines and chemokines, and degranulation products may contribute to respiratory virus-induced immunopathogenesis.