Figure 2.

6132A-PRO tumor cells expressing a dominant negative IFN-γ receptor (PRO-DNγR) are unresponsive to IFN-γ. 6132A-PRO cells were transfected with an expression vector for the transdominant-negative mutant IFN-γR α chain (20). PRO-DNγR, parental 6132A-PRO cells, and 6132A-PRO cells transfected to express I-E^k (PRO-MHC II, ref. 11) were cultured for 48 hr in the presence or absence of IFN-γ (250 units/ml) and then analyzed for expression of MHC class I and II by flow cytometry (open histograms). Controls (filled histograms) were incubated with second-step anti-Ig alone (control for MHC class I) or without antibody (control for MHC class II).