Correlation between luciferase-based IFN neutralization assay and ELISA results for the detection of auto-Abs to type I IFNs. (A) Detection of auto-Abs against IFN-α2 by ELISA versus neutralizing capacity for concentrations of 10 ng/ml and 100 pg/ml. (B) Detection of auto-Abs against IFN-β by ELISA versus neutralizing capacity for concentrations of 10 ng/ml and 1 μg/ml. (C) Detection of auto-Abs against IFN-ω by ELISA versus neutralizing capacity for concentrations of 10 ng/ml and 100 pg/ml. The panels show concordance between luciferase-based neutralization assay and ELISA in the upper-left (samples with OD <0.5 on ELISA not displaying IFN neutralizing activity) and lower-right quadrants (samples with OD >0.5 with IFN neutralizing activity) and discordance between luciferase-based IFN neutralization assay and ELISA in the upper-right (samples with OD >0.5 on ELISA but not displaying IFN neutralizing activity) and lower-left quadrants (samples with IFN neutralizing activity despite OD <0.5 on ELISA). Values below 15% are considered to be associated with the presence of neutralizing auto-Abs.