SLC15A4 is required for Toll-like receptor 7 (TLR7)- and TLR9-mediated type I interferon (IFN-I) production in plasmacytoid dendritic cells (pDCs) by the mTOR pathway, highlighting its role in regulating the immune response in the tumor microenvironment (Kobayashi et al., 2014). The gene discussed is TLR9; the disease is neoplasm.