CASP3 and infection: Microglia activation was highly increased by infection in OPN KO mice, as revealed by a decreased Iba-1 staining on day 5 pi compared to uninfected and to WT animals (Figures 8(m), 8(n), 8(o), and 8(p)), in parallel with TUNEL and caspase 3, suggesting that microglial activation is associated with more cell death.