Immediately following infection, proinflammatory responses, including production of cytokines (for example, TNFα, IL-6, and IL-1β) and chemokines (for example, chemokine (C-C motif) ligand 2 (CCL2) and CCL3), are initiated by macrophages, dendritic cells, and epithelial cells in the respiratory tract, which activate humoral and cell-mediated immune responses to promote virus clearance and protection of the host from subsequent infection. This evidence concerns the gene CCL2 and infection.