It is thus noteworthy that many of the cytokines elevated in HLH, such as IFN-gamma, IL-2, IL-6, IL-10, IL-12, and GM-CSF signal through a pathway involving the Janus kinases (JAKs) and Signal Transducers and Activators of Transcription (STATs) (Figure 1) (30). Here, CSF2 is linked to hemophagocytic syndrome.