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). This evidence concerns the gene TLR2 and bacterial infectious disease.