Gender bias in autoimmunity is influenced by microbiota

Gender bias and the role of sex hormones in autoimmune diseases are well established. In specific-pathogen free (SPF) non-obese diabetic (NOD) mice females have 1.3-4.4 times higher incidence of Type 1 diabetes (T1D). Germ-free (GF) mice lose the gender bias (female/male ratio 1.1-1.2). Gut microbiota differed in males and females, a trend reversed by male castration, confirming that androgens influence gut microbiota. Colonization of GF NOD mice with defined microbiota revealed that some but not all lineages overrepresented in male mice supported a gender bias in T1D, and protection did not correlate with androgen levels. However, hormone-supported selective microbial lineage variation may work as a positive feedback mechanism contributing to the sexual dimorphism of autoimmune diseases. Gene expression analysis suggested pathways involved in protection of males from T1D by microbiota. We compared gene expression patterns in the pancreatic lymph nodes (PLNs) between four groups of mice (two genders in SPF and GF conditions, respectively). PLNs were isolated from 9-10 week old GF and SPF male and female NOD mice with 3 mice in each group, for a total of 12 samples.