Tetramer staining and IFN-γ production of a T-cell clone and PBMCs.

(A) The left panel shows tetramer staining of a T-cell clone of which most of the T cells are specific for one peptide, revealing the presence of ∼ 87% tetramer⁺ CD8⁺ T cells (upper right quadrant). In the right panel, a well of a 96-well nitrocellulose-backed plate containing spots is shown, revealing ∼100 IFN-γ–producing T cells (∼80%) after peptide stimulation of ∼125 cells of the T-cell clone, which comes down to ∼93% IFN-γ–producing tetramer⁺ T cells. (B) Percentage tetramer staining (3.3%, left panel) and percentage IFN-γ–producing CD8⁺ T cells after peptide (RAK) stimulation and intracellular IFN-γ staining (1.6%, right panel) of PBMCs of a healthy EBV carrier.