IFN-γR2 expression and impaired STAT1-DNA-binding activity in response to IFN-γ stimulation of the patients’ cells. (A) Flow cytometry analysis of IFN-γR2 expression on the surface of EBV-B cells from 3 healthy controls (WT/WT-1, WT/WT-2, and WT/WT-3), a patient with recessive complete IFN-γR2 deficiency (RC-R2, 218delAA/218delAA), patient P1 with the recessive S124F mutation conferring partial deficiency (RP-R2, S124F/S124F), patients P2 and P3 with the recessive G141R mutation (RP-R2, G141R/G141R), a patient with recessive partial IFN-γR2 deficiency (RP-R2, R114C/R114C), 2 patients with complete recessive IFN-γR2 deficiency and surface expression (RC-R2, 382-387dup/382-387dup and RC-R2, T168N/T168N), a patient with dominant partial IFN-γR1 deficiency (DP-R1, 818del4/WT), and a patient with complete recessive IFN-γR1 deficiency (RC-R1, 523delT/523delT). These results are reproducible and representative of ≥3 independent experiments. The histograms represent the expression of IFN-γR2 (bold line) and the isotype control (gray filled). (B) Difference in mean fluorescence intensity (ΔMFI) values between specific and isotype antibody are indicated. Response of EBV-B cells to (C) IFN-γ and (D) IFN-α (10⁵ IU/mL for 20 minutes) as determined by EMSA of GAS probe-binding nuclear proteins from a healthy control (WT/WT), patients P1 with the S124F mutation (RP-R2, S124F/S124F) and P2 (RP-R2, G141R/G141R) studied here, a patient with recessive partial IFN-γR2 deficiency (RP-R2, R114C/R114C), a patient with recessive complete IFN-γR2 deficiency (RC-R2, 218delAA/218delAA), and a patient with dominant partial IFN-γR1 deficiency (DP-R1, 818del4/ WT). These results are reproducible and representative of ≥3 independent experiments.