In this study, we report that PPARδ is highly expressed in IL-10+ Bregs with a predominant surface phenotype of CD19+CD24hiIgDlo/−CD38lo or CD19+CD24hiIgDlo/−CD38hi, which present in naïve mice and can be induced by tumor formation and agonistic anti-CD40 mAb. Here, PPARD is linked to neoplasm.