Figure 8From: Standardization of cytokine flow cytometry assaysBackground cytokine-producing cells by experiment. Cytokine-positive cells in the absence of stimulus are expressed as a percentage of CD4+ or CD8+ T cells. Each symbol represents the background from a single sample processed by a single site. Medians are shown by a horizontal bar. Data from experiment 4 are for cocktails 2 and 3 only, to be comparable with experiments 1–3.Back to article page