TLR9 and Epstein-Barr virus infection: Consistent with this hypothesis, one of the major candidates as an environmental risk factor for MG is Epstein-Barr Virus, EBV infection [137], and recent works suggest that EBV infection contributes to the pathogenesis of MG within the thymus through a sustained stimulation of TLR-7 and TLR-9, thus, de-regulating innate immunity [138,139].