Treatment of mice with the S1P₁-blocking agent FTY720 counteracts immune-induced disruption of the Peyer’s patches. Mice were provided with drinking water supplemented with FTY720 and treated with poly(I:C) as in Figure 1. Organs were examined 48 hours after the last poly(I:C) injection for absolute cell numbers. Data give the mean values of n = 10 mice per group ± SEM from 2 independent experiments.