Reproducibility of T cell responses to CMV pp65 and SEB. Frozen PBMCs from 3 donors were independently thawed and cultured with CMV pp65 peptide pool or vehicle (panels A and B) or with SEB (panels C and D) by two operators at five different occasions. The expression of IL-2, INF-γ and TNF-α in CD3+CD4+ and CD3+CD8+ cells was determined by specific staining and flow cytometry analysis. Background cytokine expression from unstimulated cells was subtracted from CMV pp65 peptides-stimulated cells. Percentages of CD4+ (panel A and C) and CD8+ (panel B and D) T cells either IL-2- IFN-γ+ TNF-α-, IL-2- IFN-γ- TNF-α+, IL-2+ IFN-γ- TNF-α-, IL-2- IFN-γ+ TNF-α+, IL-2+ IFN-γ- TNF-α+, IL-2+ IFN-γ+ TNF-α- or IL-2+ IFN-γ+ TNF-α+ obtained for the three donors in ten independent experiments are presented.