Toll-like receptor (TLR)2 and TLR4 in human peripheral blood granulocytes: a critical role for monocytes in leukocyte lipopolysaccharide responses.
Leukocyte responsiveness to LPS is dependent upon CD14 and receptors of the Toll-like receptor (TLR) family. Neutrophils respond to LPS, but conflicting data exist regarding LPS responses of eosinophils and basophils, and expression of TLRs at the protein level in these granulocyte lineages has not been fully described. We examined the expression of TLR2, TLR4, and CD14 and found that monocytes expressed relatively high levels of cell surface TLR2, TLR4, and CD14, while neutrophils also expressed all three molecules, but at low levels. In contrast, basophils expressed TLR2 and TLR4 but not CD14, while eosinophils expressed none of these proteins. Tested in a range of functional assays including L-selectin shedding, CD11b up-regulation, IL-8 mRNA generation, and cell survival, neutrophils responded to LPS, but eosinophils and basophils did not. In contrast to previous data, we found, using monocyte depletion by negative magnetic selection, that neutrophil responses to LPS were heavily dependent upon the presence of a very low level of monocytes, and neutrophil survival induced by LPS at 22 h was monocyte dependent. We conclude that LPS has little role in the regulation of peripheral blood eosinophil and basophil function, and that, even in neutrophils, monocytes orchestrate many previously observed leukocyte LPS response patterns.
Sabroe
Ian
I
Section of Functional Genomics, Division of Genomic Medicine, University of Sheffield, Sheffield, United Kingdom.
Jones
Elizabeth C
EC
Usher
Lynne R
LR
Whyte
Moira K B
MK
Dower
Steven K
SK
D001491:Basophils / Q000187:drug effects / Q000276:immunology; D001769:Blood / Q000276:immunology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D029721:Drosophila Proteins; D004804:Eosinophils / Q000187:drug effects / Q000276:immunology; D006098:Granulocytes / Q000276:immunology*; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis / Q000235:genetics; D019041:L-Selectin / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000096:biosynthesis / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D016177:Macrophage-1 Antigen / Q000096:biosynthesis; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D009000:Monocytes / Q000276:immunology*; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology; D012333:RNA, Messenger / Q000096:biosynthesis; D011956:Receptors, Cell Surface / Q000096:biosynthesis* / Q000235:genetics; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
D029721:Drosophila Proteins; D016209:Interleukin-8; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D016177:Macrophage-1 Antigen; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D019041:L-Selectin