STAT1 and macrophage activation syndrome: STAT1 is significantly associated with their differentiation, which is in accordance with the established role of STAT1 in Mφ differentiation and function.[30], [31], [32] Interestingly, blood monocytes of patients with cytokine storm syndrome (MAS) display a similar increase in basal levels of pSTAT1, and their monocytes are hyperresponsive to type II IFN stimulation, resulting in even higher pSTAT1 levels.33