Antigen-specific proliferation of CMV and HIV-specific CD8⁺T cells.

PBMCs, obtained from subjects 31, 15, 12, and 17 (A-D, respectively), were CFSE labeled and incubated with either the HLA-A2–restricted CMV pp65 peptide (A) or overlapping peptides encompassing the HIV gag protein (B-D). The cells were cultured for either 6 or 48 hours and then labeled with anti–CD3 PerCP, anti–CD8 APC, and anti–IFN-γ-PE. The flow cytometric data represent gated CD3⁺CD8⁺ T cells and is demonstrated as follows: background (costimulatory antibodies alone, left), 6-hour stimulation (center, left), and 48-hour stimulation dot plots (center, right) and CFSE histogram (right). The Y-axes in the dot plots represent staining for IFN-γ. Red dots represent CD8⁺ T cells that produced IFN-γ but did not divide. Blue dots correspond to IFN-γ⁺ proliferating CD8⁺ T cells, and green dots correspond to IFN-γ⁻–proliferating CD8⁺ T cells. The numbers represent the total antigen-specific response at 6 hours. Gray dots represent CD8⁺ T cells that did not proliferate or produce IFN-γ.