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S.-H. Chung, M.-N. Kweon, H. Lee, J.-Y. Yang, E. Kim; Toll Like Receptor 4 Initiates an Innate Immune Response to Lipopolysacccharide in Human Conjunctival Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5147.
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Conjunctival epithelial cells serve as a first line of defense against pathogens presented to the innate immune system. The inflammatory response to Gram-negative bacteria is initiated by Toll-like receptor 4 (TLR4). The purpose of our study was to investigate whether a TLR4 ligand induces production of inflammatory cytokines in human conjunctival epithelial cells (HCECs) through nuclear factor kappa-B (NF-ΚB).
HCECs were stimulated with various concentrations of lipopolysaccharide (LPS). HCECs were evaluated for TLR4 expression by reverse transcriptase polymerase chain reaction (RT-PCR) and flow cytometric analysis. The innate immune response was quantified by measuring expression of the inflammatory cytokines IL-6 and IL-8. Functional NF-ΚB activation was examined using a luciferase reporter assay.
Expression of TLR4-specific mRNA as well as its corresponding protein was observed both intracellularly and on the cell surface of HCECs. Incubation of HCECs with LPS led to activation of the NF-ΚB transcription factor and secretion of IL-6 and IL-8 in a dose dependent manner. Blockade of TLR4 and TRAF6 activity abolished induction of the inflammatory response to LPS in HCECs. LPS did not induce the expression of TLR4 in HCECs.
Our results demonstrated that surface expression of TLR4 in human conjunctival epithelial cells was able to elicit a TLR4-mediated innate immune response and contribute to an inflammatory environment on the ocular surface.
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