Table 1.

Main inflammasome‐forming receptors in epithelial cells

Subfamily	Receptor	Requirement for ASC	Main activating signal	Main epithelia involved
NLRP	NLRP1	Yesa	Anthrax toxin and ATP	Oral, airway22, 23, 24
	NLRP3	Yes	Ionophores, crystals, ATP, bacterial toxins	Oral, airway, intestinal, skin22, 23, 25, 26
	NLRP6b	Yes	Microbiota‐modulated metabolites (taurine)	Intestinal27
	NLRP9b	Yes	Rotavirus dsRNA	Intestinal28
NLRC	NLRC4/IPAF	Yesa	Flagellin (in mouse)/Type III secretion system (in human)	Intestinal29
Other inflammasome‐forming sensors	AIM2	Yes	dsDNA	Oral, skin23, 30

Not all the inflammasome‐forming receptor proteins require the adaptor protein apoptosis‐associated speck‐like protein containing a caspase activation and recruitment domain (ASC) to activate caspases‐1, however, when present, ASC potentiates inflammasome activity. Also shown the main activating signals and epithelial distribution.

^aBoth nucleotide NACHT, LRR and PYD domains‐containing protein 1 (NLRP1) and NLRC4 protein have a caspase recruitment domain and have shown activity in the presence or absence of ASC.9, 31

^bThe ability of NLRP6 to form inflammasomes has only been suggested but not directly shown.