Flow cytometry analysis of binding of p540⁺ tetramers to circulating CD8⁺ T lymphocytes. Lymphocytes were from (A) 1 HLA-A2⁺ cancer patient (no. 1); (B) 1 HLA-A2^- cancer patient (no. 17); (C) 1 HLA-A2⁺ healthy subject; (D) 1 HLA-A2^- healthy subject; (E) 1 p540-specific CTL line (generated from patient no. 16 and used as positive control); and (F) 1 EBV-specific CTL line (used as further negative control).