IFNG and macrophage activation syndrome: Compared to KD patients, the KFD group without MAS had a significantly higher serum IFN-γ level (p = 0.007) and IFN-γ/IL-6 ratio (p = 0.0003), and much lower levels of serum IL-6 (p = 0.018), TNF-a (p = 0.032), and IL-4 (p = 0.028) (Table 3 and Fig. 1D-F).