Figure 3.

Up-regulation of HLA-E heavy chains by IFN-γ and NKL lysis. (A) 221 and K562 cells, either untreated or treated for 72 hours with 200 U/ml of recombinant IFN-γ, were tested by flow cytometry with antibodies to class I heavy chains (W6/32) and β₂m (Namb-1). An antibody to HLA class II molecules (KUL/05) was used as a control for IFN-γ responsiveness of 221 cells. (B) Control and IFN-γ-treated (as previously mentioned) 221 and K562 cells were surface-labeled with biotin and HLA-E was revealed as described in the legend to Figure 2. (C) Control and IFN-γ-treated (as previously mentioned) 221 and K562 cells were tested for their susceptibility to NKL lysis at the indicated E/T ratios. The experiment was repeated three times.