IFNG and systemic lupus erythematosus: However, IFN-γ production in the positive control tube (mitogen) and ex vivo IFN-γ production (mitogen minus nil) was decreased in patients with active SLE (median 2.93 vs. 11.15 IU/mL, p < 0.001; 0.92 vs. 11.06 IU/mL, p < 0.001) (Table 2).