The reduction in class I MHC expression is due to TAP2 deficiency. Fusion of EBV-A, EBV-B, and EBV-C with various B-cell lines defective either for the TAP1 and TAP2 subunits (.174) or none of them (.45). Total mixture of cells was analyzed by FACS. Fused cells were identified by HLA-A3 expression. Staining with HLA-A3 is on the y-axis, and forward scatter is on the x-axis. One representative experiment is shown of 3 performed.