Recovery of CD8 responses to viruses. (A) Recovery of CD8 responses against EBV. ▪ represents time points at which a significant (> 0.1% above isotype) tetramer-positive population was identified in the peripheral blood of recipients; □, time points at which no tetramer-positive cells were observed. The arrows indicate EBV viremia. Time points at which patient went off study for relapse (R) or mixed chimerism (MC) are shown. Crosses indicate time points at which patients died. (B) CD8 responses against CMV. Schema as in panel A. (C) Flow cytometric analysis of peripheral blood from patient P13 at 6 months after transplantation (bottom 2 panels) and his donor (top 2 panels) using CD8-FITC/tetramer-PE staining. The left panels show samples stained with the HLA-A2-NLV tetramer (pp65), and the right panels show samples stained with the HLA-B8-ELR tetramer (IE1). The percentage of CD3⁺8⁺ T cells that were tetramer positive is shown.