CCL2 and severe acute respiratory syndrome: Clinically, the serum levels of proinflammatory cytokines (IFN-γ, IL-1, IL-6, IL-12, and transforming growth factor β) and chemokines (CCL2, CXCL10, and IL-8) were found to be significantly higher in patients with severe SARS than in patients with nonsevere SARS (27).