CXCL8 and macrophage activation syndrome: In contrast, few severe patients experience a macrophage activation syndrome (MAS) (8), followed by respiratory and even multi-organ failure (9, 10); and a cytokine release syndrome (CRS) characterized by large amounts of pro-inflammatory cytokines like interleukin (IL)-1, IL-6, IL-8 and tumor necrosis factor (TNF).