Prevention of EBV-specific CD8⁺ cell loss by CD28 costimulation after a 3-day culture.

Data are expressed as percentage of tetramer⁺ cells in CD8⁺ cells from fresh (black bars) or 3-day–cultured PBMCs after CD3/IL-2 (white bars) or CD3/CD28/IL-2 (hatched bars) activation.