Table 1.

Key molecules and their functions in epithelial-commensal cross talk

MAMP	Microbe-associated molecular pattern	Conserved molecular structures characteristic to microbes but not eukaryotes (eg, bacterial CpG DNA, LPS)
PRR	Pattern-recognition receptor	Innate immune molecules that recognize MAMPS and initiate immune responses
TLR	Toll-like receptor	Group of PRRs with a central role in the intestinal epithelium
NF-κB	Nuclear factor κB	Transcription factor controlling expression of a wide variety of proinflammatory genes activated by TLR signaling
IκB	Inhibitor of κB	Inhibitory molecule attached to NF-κB phosphorylation and ubiquitination of IκB leads to nuclear translocation and activation of NF-κB
NEMO	Nuclear factor κB essential modulator	Regulatory molecule controlling IκB degradation
TOLLIP	Toll inhibitory protein	Inhibits inflammatory responses resulting from TLR activation

CpG—cytosine-guanide; LPS—lipopolysaccharide.