PTGDS and infection: On day 7 p.i., coincident with the peak of N. brasiliensis–induced tuft cell hyperplasia (Gerbe et al., 2016; von Moltke et al., 2016), there was a significant infection-induced increase in PGD2 (Fig. 5 a), but not other prostaglandins or thromboxane (Fig. S4 a), in small intestinal tissue detected by mass spectrometry.