CXCL9 and severe acute respiratory syndrome: Cytokines such as interleukin (IL)-1β, IL-6, IL-12, interferon-gamma (IFN-γ), transforming growth factor beta (TGF-β), and IFN-α and chemokines C–C motif chemokine ligand 2 (CCL2), C-X-C motif chemokine ligand 9 (CXCL9), CXCL10, macrophage inflammatory protein-1 alpha (MIP-1α), and IL-8 have been reported to be substantially elevated in severe SARS patients [25,26,101,102], whereas mild patients were found to have an increased production of T-helper 1 cell (Th1)-related cytokines IL-2, IL-12, IFN-γ, and tumour necrosis factor alpha (TNF-α) [54,67].