Figure 1.

Human CD8⁺ CTL specific for the cytomegalovirus N9V Ag capture CD4 from T2 target cells. Human CD8⁺ T cells were incubated for 1 hour with T2 cells, which express CD4 and HLA-A2.1 naturally, that had been loaded (+Ag) or not (−Ag) with the N9V peptide. Cells were then analyzed by flow cytometry for CD4 and CD8 expression. Shown are overlapping histograms of CD4 expression on gated CD8⁺ T cells. Similar results were obtained in 3 experiments.