Upregulated expression of cytokines, chemokines and growth factors was commonly observed in patients and animals with lymphopenia induced by viral infection, including IL-2, IL-6, IL-12, IL-18, IL-1β, IFN-γ, CCL2/MCP-1, CXCL1, CXCL8/IL-8, CCL3/MIP-1-α, CCL7/MCP-3, CXCL10/IP-10 and CXCL9/MIG [17,53,128]. Here, CCL2 is linked to lymphopenia.