Figure 3. The APLP2^high phenotype identifies EWS cells with consistently relatively low MHC class I surface expression upon irradiation. (A-B) EWS cells exposed to the indicated doses of γ rays were examined by flow cytometry for the co-expression of APLP2 and folded MHC class I molecules (using the W6/32 antibody) on their surface. Three cell subpopulations were identified: APLP2^highMHCI^low, APLP2^intMHCI^high, and APLP2^lowMHCI^high cells. MHC class I-dependent fluorescence (in terms of mean fluorescence units, MFU) is depicted for each subpopulation of TC71 (A) and A673 (B) cells. Error bars denote SD (n = 6 experimental replicates within 1 representative experiment out of 3 independent ones performed that yielded similar results, with 1 experiment including both TC71 and A673, and 2 experiments including 1 of the 2 cell lines). Representative dot plots can be found in Figure S3.