PPIG and infection: D- WT and D- Cyp KO mice had very low Citrobacter-specific IgG1 and IgG2c responses at both d14 and d28 post-infection (Figures 2A,B) The IgG1 or IgG2c C. rodentium-specific response was similar in D+ WT and D+ Cyp KO mice at either d14 or d28 post-infection (Figures 2A,B).