TLR2 and infection: After infection with A. hydrophila, the transcriptional levels of TLR1, TLR2, caspase 8, MyD88, FADD, TOLLIP isoform 1 and TOLLIP isoform 2 were all significantly up-regulated in the kidney, indicating that bacterial infection induced the activation of TLR signaling pathway in the yellow catfish (Figure 10).