Reconstitution of CMV-specific, tetramer-positive cells and the occurrence of CMV-viremia in recipients of HSC grafts from CMV-negative donors. Top panel: patient 11. Middle panel: patient 12. Bottom panel: patient 13. ○ indicates number (G/L) of lymphocytes. Fractions in the graphs show the number per milliliter of tetramer-positive/CD8⁺ T lymphocytes at the moment indicated by arrowheads. Shaded areas represent the viral load expressed as either positive or negative for the pp65 antigen or as number of viral copies per milliliter of plasma.