Amezcua-Guerra LM, et al. - The relationship between serum type III (γ) interferons (IFN-γ) and disease activity in systemic lupus erythematosus (SLE) is evaluated in this study. Interferon γ3, a subtype of type III IFNs, is related to the extent of lupus activity, specifically with active serosal and cutaneous disease. This connection could be mechanistically associated with anti-Ro/SSA antibodies.

Methods

• In this study, they measured serum levels of IFN-γ1, IFN-γ2, and IFN-γ3.
• A sum of 93 SLE patients and 67 healthy individuals were enrolled in this study.
• The relationship with overall disease activity, organ-specific damage, and SLE-related antibodies were evaluated.

Results

• In this study, median IFN-γ1 levels were 0 pg/mL (range, 0-510 pg/mL) and 0 pg/mL (0-171 pg/mL; P = 0.814) in SLE patients and control subjects, respectively.
• These figures were 0 pg/mL (0-28 pg/mL) and 0 pg/mL (0-43 pg/mL; P = 0.659) for IFN-γ2, and also 83 pg/mL (0-965 pg/mL) and 42 pg/mL (0-520 pg/mL; P = 0.002) for IFN-γ3, respectively.
• As per the Systemic Lupus Erythematosus Disease Activity Index categories, IFN-γ3 levels were 44 pg/mL (0-158 pg/mL) in quiescent, 117 pg/mL (0-344 pg/mL) in mild, 79 pg/mL (0-965 pg/mL) in moderate, and 78 pg/mL (0-329 pg/mL) in severe disease, with the highest levels found in patients with serosal or cutaneous involvement.
• In line with this, IFN-γ3 levels were inversely correlated with C3 (ρ = -0.44; 95% confidence interval, -0.62 to -0.20; P = 0.0003) and C4 (ρ = -0.40; 95% confidence interval, -0.59 to -0.15; P = 0.0001) complement proteins.
• In addition, higher IFN-γ3 levels were found in patients positive for anti-Ro/SSA antibodies than in those negative for that antibody (122 pg/mL [0-965 pg/mL] vs. 0 pg/mL [0-165 pg/mL]; P = 0.001).
• The concentration of IFN-γ3 also was higher in patients receiving glucocorticoids (104 pg/mL [0-965 pg/mL] vs. 30 pg/mL [0-165 pg/mL]; P = 0.009), and a dose-related impact was observed.