Table 2.

TLR-expression of different pulmonary target cells in respiratory infections and their ligands

TLR	AEC	BEC	TrEC	DC	AM	LEndC	LFib	ASmC
TLR-1	+	+	+	+	+
TLR-2	+	+	+	+	+	+	+	+
TLR-3	+	+	+	+	-		+	+
TLR-4	(+)	(+)	+	+	+	+	+	+
TLR-5	+	+	+		-
TLR-6	+	+	+		+
TLR-7				++	+
TLR-8					+	+
TLR-9	+	+	+	++	-		+

TLR Toll-like receptor, AEC alveolar epithelial cells, BEC bronchial epithelial cells, TrEC tracheal epithelial cells, DC dendritic cells, AM alveolar macrophages, LEndC lung endothelial cells, LFib lung fibroblasts, ASmC airway smooth muscle cells