CD137-dependent activation of microglia has been reported to be involved in the development of experimental autoimmune encephalomyelitis (Tanga et al., 2005; Cao and DeLeo, 2008; Yeo et al., 2012), yet CD137-independent, CD137L-mediated activation of microglia has not been investigated. Here, TNFRSF9 is linked to experimental autoimmune encephalomyelitis.