CCL2 and macrophage activation syndrome: Not only highly elevated CRP and ferritin, which are key to the diagnosis of MAS/sHLH, are also elevated in many severe COVID-19 pneumonia cases, the cytokine profile in MAS/sHLH resembles that of COVID-19 patients, with increased levels of IL-1β, IL-2, IL-6, IL-17, IL-8, TNF, and MCP1.31, , , , –36 This has generated tremendous interest in anti-cytokine strategies aimed at dampening exaggerated immune responses.31,37, , –40