TLR7 and infection: However, in HT-29 cells the levels of IRF7 decreased marginally at 36 hrs, but were shown unchanged at 24 hrs p.i. (Fig 2), suggesting that TLR signaling may remain intact and be unaffected, and that TLR7/8 signaling may also function early and decrease only at the late stage of infection in HT-29 cells.