SPHK2 and infection: Subsequent determination of S1P levels in plasma 6 h, 24 h and 14 d post infection revealed an early drop of 40% (Δ 416 nM) in wt mice, 45% (Δ 163 nM) in SphK1−/− mice and 15% (Δ 362 nM) in SphK2−/− mice (Figure 1A–C).