Commensal regulation of T cell survival through Erdr1

The commensal microbiota influences many aspects of immune system regulation, including T cells, but molecular details of how this occurs are largely unknown. Here we review our findings that the microbiota regulates Erdr1, a secreted apoptotic factor, to control T cell survival. Erdr1 is highly upregulated in CD4+ T cells from germfree mice and antibiotic treated animals, and our study shows that Erdr1 is suppressed by the microbiota via Toll-like receptor signaling and MyD88 dependent pathways. Erdr1 functions in an autocrine fashion and promotes apoptosis through the FAS/FASL pathway. Suppression of Erdr1 leads to survival of autoreactive T cells and exacerbated autoimmune disease in the EAE model, and overexpression of Erdr1 results in lessened disease. This novel T cell apoptotic factor has implications for autoimmunity, cancer biology, and invasive pathogens and thus represents a novel therapeutic target in disease.