Chemical complementation with kifunensine of the response of the patients’ SV40 fibroblasts to IFN-γ. SV40 fibroblasts from a healthy control (WT/WT), 2 patients with recessive complete IFN-γR2 deficiency with detectable surface expression of a nonfunctional IFN-γR2 (RC-R2, 382-387dup/382-387dup and RC-R2-T168N/T168N), a patient with recessive partial IFN-γR2 deficiency (RP-R2, R114C/R114C), patient P1 with the S124F mutation (RP-R2, S124F/S124F), patient P3 with the G141R mutation (RP-R2, G141R/G141R), and a patient with recessive complete IFN-γR2 deficiency and no expression of the receptor at the cell surface (RC-R2, 278delAG/278delAG) were incubated for 72 hours in complete culture medium without (gray filled) stimulation, or with (A) 2.4 × 10⁴ IU/mL IFN-γ (bold line) or (B) 100 IU/mL IFN-γ (dashed line) with or without 1.5 mM NB-DNJ, 2 mM castanospermine, or 160 μM kifunensine. They were analyzed 48 hours later. The surface expression of HLA-DR molecules was determined by flow cytometry with a specific antibody.