Fig 5

Cytokine production by tetanus- and diphtheria-specific CD4⁺ memory T cells. PBMCs were stimulated for 6 h with 10 μg/ml tetanus (a c) or 10 μg/ml diphtheria toxoid (b d) in the presence of Brefeldin A (5 h). Frequencies of CD4⁺ memory T cells producing IFN-γ, TNF-α, IL-2, IL-4, IL-10, IL-17, IL-21, TGF-β and GM-CSF were measured by flow cytometry. Data from young (a b; n = 17) and elderly (c d; n = 27) adults are shown. A representative example for the gating strategy is shown in Additional file 2: Figure S1