Endotoxaemia modulates Toll‐like receptors on leucocytes in humans

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Abstract
Summary. The modulation of Toll‐like receptors (TLR) 1, 2 and 4 was studied during experimental human endotoxaemia. Healthy volunteers received 2 ng/kg of lipopolysaccharide (LPS) endotoxin (n = 10). TLR1, 2 and 4 expression occurred on monocytes and neutrophils, with monocytes expressing higher baseline levels of TLR2. LPS infusion downmodulated TLR4 expression on neutrophils, with maximal downregulation occurring at 24 h (−62% from baseline; P < 0·03 versus baseline). Monocyte TLRs were upregulated in vivo (TLR1 and 2), and in vitro (TLR1, 2 and 4) 8 h after LPS bolus (P < 0·05 versus baseline). Therefore, neutrophils and monocytes differentially express surface TLRs, and endotoxaemia differentially regulates TLR expression.