Dysbiosis results in reduced cecal SCFAs and supplementation with butyrate attenuates anti-FVIII immune response. (A) Levels of the cecal SCFAs acetate, butyrate, and propionate were quantified by NMR at 6 weeks of age, before FVIII infusion, and compared between ampicillin-treated (n = 5) and control (n = 4) mice. (B) In a separate experiment, mice were maintained in regular housing conditions and supplemented with 100 mM butyrate in the drinking water starting from 3 weeks of age (n = 7). They were then challenged with FVIII as previoulsy described. Plasma was analyzed for FVIII-specific IgG and compared with plasma of mice receiving only water (n = 10). The means and standard deviations of SCFA levels and FVIII-specific IgG were compared by using the unpaired, 2-tailed Student t test and the Mann-Whitney U test, respectively. **P < .01; ***P < .001; ****P < .0001.