IRAK1 and meningococcal infection: Based on these results, our data lean toward a biphasic model to promote apoptosis by ST-11 isolates (Figure 9): First, LOS mediates early activation of NF-κB during meningococcal infection in TLR4/MyD88/IRAK1-dependent manner leading to induction of expression and early secretion of the pro-inflammatory cytokine TNF-α and its receptor TNFR1 (Figure 9A).