Functional capacity and activation status of virus-specific CD8⁺ T cells in the BM. (A) BM-derived EBV-specific CD8⁺ T cells but not CMV-specific CD8⁺ T cells have greater IFN-γ response compared with blood counterparts. Cells were stimulated with class I–restricted RAKFKQLL peptide for EBV response and QIKVRVDMV peptide for CMV response for 6 hours, followed by intracytoplasmic staining for IFN-γ. Example flow cytometry profiles show virus-specific response by CD8⁺ T cells. (B) Graph shows the ratio of IFN-γ response in the blood and BM in 3 different subjects. A negative value means there is more IFN-γ producing cells in the BM. (C) The table shows the mean fluorescence index of IFN-γ–producing cells. (D) A representative plot of CD45RO expression on tetramer-positive CD8⁺ T cells. After gating on CD8⁺ T cells, the dual expression of tetramer and CD45RO were analyzed. (E) Expression of CD45RO on CMV- and EBV-specific CD8⁺ T cells in paired blood and BM samples.