We show Gram-negative bacterial infection upregulates Siglec-E expression via the TLR4/MyD88/JNK/NF-κB/AP-1 signaling pathway, whereas infection with Gram-positive bacteria downregulates Siglec-E expression via the TLR2/RANKL/TRAF6/Syk signaling pathway. This evidence concerns the gene MYD88 and infection.