Selected examples of innate immune receptors implicated in autoimmunity and their endogenous and exogenous ligands

Receptor	Endogenous ligands	Exogenous ligands
Toll-like receptors
TLR2 (PM)*	HMGB1	Lipoteichoic acid, peptidoglycan (muramyl dipeptide)
TLR3 (E)	Cellular dsRNA (e.g. U1 RNA)	Viral dsRNA, poly(I:C)
TLR7 (E)	Cellular ssRNA (e.g. U1 RNA)	Bacterial ssRNA, viral ssRNA
TLR9 (E)	Cellular dsDNA with unmethylated CpG sequences	Bacterial dsDNA with unmethylated CpG sequences
NOD-like receptors
NLRP3 (C)	Uric acid crystals†, cholesterol†	Muramyl dipeptide§, bacterial RNA§, poly(I:C)§, alum†, silica†, staphylococcal α-hemolysin†, influenza virus†
AIM2 (C)	Cellular dsDNA	Bacterial dsDNA (e.g. vaccinia, Francisella)

^*Location: PM, plasma membrane; E, endolysosome; C, cytoplasm

^§Acts via TLR and NFκB, which increases transcription of NLRP3 (“signal 1”)

^†Acts directly on NLRP3 via ATP and possibly decreased intracellular K⁺ or pore formation (“signal 2”)

Bold, involved in pristane-induced lupus