Using wild-type (wt) and Rag1-deficient (Rag1-/-) mice, here we examined the effects of orally administered B. uniformis CECT 7771 on innate and adaptive immune components of the intestinal epithelium and lamina propria to identify the immune players responsible for its ability to re-establish the metabolic balance in obesity. This evidence concerns the gene RAG1 and obesity due to melanocortin 4 receptor deficiency.