IFNG and systemic lupus erythematosus: The results revealed that the anti-IFN-γ IgG levels were significantly higher in SLE patients with severe infections (0.51 ± 0.27) than those in SLE patients without severe infections (0.37 ± 0.09, p < 0.01), RA (0.30 ± 0.10, p < 0.001), AS (0.32 ± 0.10, p < 0.001), and HC (0.33 ± 0.09, p < 0.001) (Fig. 1A).