CD4 and influenza: In contrast, a significant influenza-driven recall response was only generated in the CD4+CD8+ subset (6±1% CFSElow cells, P<0.01, n = 3), but not in the CD4+CD8− and CD4−CD8+ subsets (1±0% and 2±0.3% CFSElow cells, P>0.94, n = 3), in pigs vaccinated with the non-adjuvanted whole vaccine (Figure 3B–D).