Abstract Similar to humans, lupus incidence is higher in female than male NZBxNZW1(BWF1) mice, and castration abolishes male protection implicating androgens in disease suppression. Gut microbiota and metabolite compositions differ between female and male BWF1 mice; males have higher abundance of Bacteroides and the metabolites, phytol and phytanic acid (RXR agonists that can increase retinoic acid, RA). Male cecal transfers into females suppress disease which correlates with an increase in Bacteroides in recipients. In addition, female gut CD103+ dendritic cells (CD103+DC) have decreased ability to induce pTreg due to an RA deficiency (decreased RALDH2) that can be restored by male cecal transfer. The goal of this project was to study androgen effects on these processes. We found that male castration altered microbiota and metabolite compositions similarly to those found in female mice, e.g., reduced Bacteroides, and phytol and phytanic acid abundance. Castrated male cecal transfer did not suppress disease or increase Bacteroides abundance in recipients. As in females, castrated male CD103+DC had decreased ability to induce pTreg (decreased RALDH2) but induced high levels of IFNγ. And although androgen receptor mRNA was undetectable in CD103+DC, male mice treated with androgen receptor inhibitor (flutamide) had the same negative effect on CD103+DC function as castration, suggesting androgens affect CD103+DC indirectly. Interestingly, flutamide-treated and castrated male microbiota looked very similar, e.g., reduced Bacteroides. These data suggest that androgens in males increase Bacteroides abundance via receptor signaling in host cells that may in turn play a role in enhancing immunoregulation and suppressing lupus.