Expression of ERAP1 in escape variants restores recognition by TCR-IV T cells. (A) 1575 cells were transduced with either pMP71-ERAP1-IRES-GFP or pMP71-IRES-GFP and GFP sorted. Histograms indicate GFP expression at days 10 and 20 after sort. (B) The picture shows ERAP1, pSTAT1, LMP2, LMP7, MECL-1, and β-actin WB (single blot) for proteins from pMP71-ERAP1-IRES-GFP stably transduced 1575 GFP-selected cell clones (Cl1, Cl2, and Cl4) compared with 1575 and 16.113p cells (±IFN-γ pretreatment; 100 ng/48 h). One representative of two experiments is shown. (C) The graph shows levels of secreted IFN-γ by TCR-I– and TCR-IV–transduced OT-1/Rag^−/− T cells after co-culture with parental 16.113p cells, 1575, the ERAP1-overexpressing 1575 clones (Cl1 and Cl4), and the ERAP1-negative clone (Cl2) measured by ELISA (E:T/2:1). Combined data from three experiments are shown, and error bars indicate SD.