CCL2 and susceptibility to pneumonia measurement: There was sustained activation of the proinflammatory cytokines (IL-6, CXCL8/IL-8, CCL2/MCP-1, sTNFR-1) in severe pH1N1 pneumonia; the CXCL10/IP-10, CXCL9/MIG and IL-17A responses remained largely suppressed during the hospital course.