Heterologous prime-boost improves the quality of PSA-specific T cell responses. BALB/c mice (6/group) were treated as described for Figure 1. Spleens were harvested 14 days after the last treatment, and pooled splenocytes were restimulated overnight with PSA OPL or controls (controls not shown). The cells were stained for intracellular IFNγ, TNFα, and IL-2 prior to flow cytometric analysis. (A) The pie charts are weighted in size to reflect the numbers of detected cells (total numbers of PSA-specific CD8 per million T cells are indicated below each chart, % of respective T cell populations can be found in Additional file 1: Table SD1). (B) Amount of IFNγ production on a per cell basis as measured by mean fluorescence intensity (MFI). Graphs show representative data of two independently performed experiments.