To further explore the extent of LOS signaling pathway downstream TLR4 in the apoptosis promoted by the invasive ST-11 isolates, Hec-1B cells were knocked-down for functional MyD88 or TRIF by transfecting either TIR domain and apoptosis was analyzed after 9 h of infection in comparison with cells transfected with the empty vector control. This evidence concerns the gene TLR4 and infection.