Serum IFN-γ levels in untreated patients with active juvenile rheumatoid arthritis (JRA) and healthy controls (HC). A scatter plot of serum IFN-γ concentrations in 4 patients with active disease (AD) and 13 HC is shown. The values for 11 HC that were < 1.4 pg/ml (the limit of detection of the assay) are represented by triangular symbols that appear as the lowest value in the distribution. Average values in a given population are represented as a horizontal line. Concentrations are shown in pg/ml on a log scale.