In T1D studies, Tlr2 or Tlr9 deficiency in nonobese diabetic (NOD) mice led to protection from T1D development,11–14 whereas Tlr4 deficiency accelerated disease progression.15,16 TLR7, another member of the TLR family, is mainly expressed in immune cells4,5,17 and can recognize single-stranded RNA (ssRNA), a common feature of viral genomes.18 However, it is unclear what role TLR7 plays in the context of T1D. Here, TLR9 is linked to type 1 diabetes mellitus.