Fig. 4.

Impaired IFN-γ production in ISG15^−/− patients and rescue by exogenous ISG15. Cytokine production in the supernatants of whole-blood cells from local controls (n=29), travel controls (n=9), ISG15^−/− (n=3) and IL12RB1^−/− patients (n= 58), left unstimulated or stimulated with BCG alone or BCG plus cytokine (indicated), as detected by ELISA (A to C); alternatively, recombinant human ISG15 was added at the same time or 24 h before whole-blood activation by BCG and IL-12 (D). The amounts of cytokine secreted are normalized for 10⁶ PBMC on a logarithmic scale, and medians are indicated by solid bars. Differences in log-transformed IFN-γ levels after stimulation with BCG + IL-12 were assessed 1) between ISG15^−/− subjects and travel controls in Student's t-test (A), and 2) between ISG15^−/− subjects before and after adding recombinant human ISG15 by two-way analysis of variance, to take into account both activation by recombinant ISG15 and activation time (D). IFN-γ secretion was measured in whole blood stimulated with vehicle (−), BCG or BCG plus IL-12, in the presence of vehicle (−), a blocking antibody against ISG15, or an IgG1 isotype control (E).