Table.

Receptors and roles of well-characterized alarmins.

Alarmins and their receptors		Biological activities and functions
AMPs		Antimicrobial effects
Defensins (α, β, and θ)	CCR2, CCR6, TLR4	Leukocytes recruitment
Cathelicidins (eg, LL-37 and CRAMP)	FPRL1/FPR2,TLR7, 8, 9	Cytokine induction
EDN and others	TLR2	APC/DC activation Promotion of immune responses Inflammation
DNA binding proteins		Regulation of gene expression
HMGN1	TLR4	Leukocytes recruitment
HMGB1	CXCR4, RAGE,	Cytokine induction
IL-1α	TLR2, 4, 7, 8, 9 CD24	APC/DC activation
IL-33	IL-1R ST2	Promotion of immune responses Inflammation
HSP		Protein protection
HSP70, 90, 96	CD14, CD40, CD91, TLR2, 4 scavenger receptors (SRA1)	APC/DC activation Treg polarization Inflammation
Ion-binding proteins		Leukocytes recruitment
Lactoferrin	RAGE, TLR2, 4	Cytokine induction
S100 A8, A9	RAGE, TLR4	APC/DC activation Promotion of immune responses Inflammation
Others		Leukocytes recruitment
ATP and others	P2Y2, 6, 12, P2X7	Cytokine induction APC/DC activation Inflammation

APC/DC = antigen-presenting cells/dendritic cells; AMP = antimicrobial peptides and proteins; ATP = adenosine triphosphate; CCR = CC chemokine receptor; CD = cluster of differentiation; CRAMP = cathelin-related antimicrobial peptide; CXCR = CXC chemokine receptor; EDN = eosinophil-derived neurotoxin; FPR = formyl peptide receptor; HMGB = High-mobility group protein with a ‘Box’ domain; HMGN = High-mobility group protein with a ‘nucleosome-binding’ domain; IL = interleukin; RAGE = receptor for advanced glycation end-products; TLR = Toll-like receptor; Treg = regulatory T cell.