Induction of cytokine production in human T cells and monocytes by highly purified lipoteichoic acid: involvement of Toll-like receptors and CD14.
BACKGROUND
The pro-inflammatory potential of lipoteichoic acid (LTA) from Staphylococcus aureus is controversial. The present study was undertaken to examine the ability of highly purified and characterized S. aureus LTA to stimulate the production of pro-inflammatory cytokines in human leukocytes at both mRNA and protein level, and to study the involvement of Toll-like receptors (TLRs) and CD14 in this response.


METHODS
Purified LTA was administered to whole human blood ex-vivo (or primary adherent monocytes) and the cytokine response assessed in plasma by EIA. Cytokine mRNA was measured by RT-PCR on leukocyte subsets isolated following stimulation. To study the involvement of specific receptors for LTA signaling, CHO cells transfected with CD14 and/or TLR2, TLR4 were used, as well as antibodies directed against these receptors.


RESULTS
Addition of highly purified LTA to human whole blood or primary adherent human monocytes elicited a time and concentration dependent release of tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), IL-6 and IL-8. Messenger RNA encoding TNF-alpha, IL-1 beta and IL-6 seemed to be accumulated in monocytes and T cells, but not in granulocytes and B cells. Expression of TLR2, but not TLR4, in chinese hamster ovary cells conferred responsiveness to LTA. However, antibodies directed towards TLR2 (clone TL2.1) or TLR4 (clone HTA125) failed to inhibit TNF-a release induced by LTA in both the whole blood model and in adherent monocytes. In contrast, blockade of the CD14 receptor with MAb18D11 strongly attenuated the LTA induced release of TNF-alpha in both models.


CONCLUSIONS
We propose that (i) LTA from S. aureus triggers the release of cytokines during staphylococcal infections, and (ii) both monocytes and T cells contribute to cytokine production induced by LTA. TLR2 may mediate cellular activation by LTA, but the functional significance of this receptor during staphylococcal infections remains elusive.
Ellingsen
Espen
E
Institute for Surgical Research, Rikshospitalet - National Hospital, N-0027 Oslo, Norway.
Morath
Siegfried
S
Flo
Trude
T
Schromm
Andra
A
Hartung
Thomas
T
Thiemermann
Christoph
C
Espevik
Terje
T
Golenbock
Douglas
D
Foster
Daniel
D
Solberg
Rigmor
R
Aasen
Ansgar
A
Wang
Jacob
J
D000199:Actins / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D016466:CHO Cells; D002448:Cell Adhesion; D002478:Cells, Cultured; D006224:Cricetinae; D016207:Cytokines / Q000096:biosynthesis* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D029721:Drosophila Proteins; D006801:Humans; D007700:Kinetics; D018950:Lipopolysaccharide Receptors / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000378:metabolism*; D013682:Teichoic Acids / Q000494:pharmacology*; D013997:Time Factors; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014162:Transfection
D000199:Actins; D000911:Antibodies, Monoclonal; D016207:Cytokines; D029721:Drosophila Proteins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D013682:Teichoic Acids; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; C009900:lipoteichoic acid