Welcome to the Microgenderome

The gender bias observed in numerous diseases has long been understood as an entirely host-intrinsic factor. It is one of the many puzzling features of some autoimmune conditions (inappropriate immune responses that attack self antigens and destroy host tissue) including type 1 diabetes mellitus, in which sex hormones affect disease susceptibility and severity ( 1 , 2 ). On page 1084 of this issue, Markle et al. ( 3 ) introduce an astonishing twist to this view, suggesting that gender bias may be exercised and/or reinforced by the commensal microbiota of the host. This extrinsic, albeit commensal, factor appears to regulate sex hormone levels and arguably the gender bias observed in type 1 diabetes mellitus. The finding contributes to an expanding field of translational research aiming to convert our growing knowledge of the host-microbiota relationship into therapeutic approaches.