To confirm these inferences, we used cell transfer experiments combined with a prime–boost live vaccination system in which CD8+ and CD4+ T cells isolated from mice that had recovered from PyNL infection after two homologous boosts with PyL transferred protection from an otherwise lethal infection with PyL to the recipient mice (Figure 1E,F) (Imai et al., 2010). Here, SFRP4 is linked to infection.