Figure 3. Antigen-specific human IFNγ responses elicited by cross-conserved epitopes before and after 2010–2011 TIV vaccination. Cross-conserved epitopes were assayed for T cell reactivity by cultured IFNγ ELISpot assay using PBMCs isolated from normal human donors before and three weeks after TIV vaccination (n = 16). Assays were performed following a nine-day T cell expansion after stimulation with cross-conserved influenza epitopes. The numbers of SFC over background per million PBMCs that secrete IFNγ in response to individual and pooled influenza HA and NA cross-conserved epitopes are presented. Individual subject average responses are represented by dots and the average response across subjects by white bars. The 50 SFC over background per million PBMCs cutoff is denoted by the dotted line.