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K. Kojima, M. Ueta, Y. Hozono, J. Hamuro, S. Kinoshita; Response of Human Corneal Epithelial Cells to Various Toll–Like Receptor 2 Ligands . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1279.
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© ARVO (1962-2015); The Authors (2016-present)
We previously reported that human corneal epithelial cell (HCE) does not respond to toll–like receptor (TLR) 2 ligand, peptidoglycan (PGN), and this absence of response contributes to the immunosilent environment to commensal bacteria inhabiting on ocular surface (Ueta et al., 2004). Recently, variety of TLR2 ligands are reported. We examined the response of HCE to these newly reported TLR2 ligands in vitro.
The human corneal epithelial cell line transformed with SV40 (HCE–T) were stimulated with heat killed Listeria monocytogenes (HKLM), synthetic lipoproteins (Pam3CSK and FSL–1), PGN, purified lipoteichoic acid from Staphylococcus aureus (LTA–SA). HCE–T was also stimulated with IL–1α as positive control. Supernatants were harvested after twenty–four hours of exposure to these ligands and were examined for the production of IL–6 and IL–8 by ELISA. IL–6, IL8, and TLR2 mRNA expressions of HCE–T after one hour of exposure to each ligands were also analyzed using quantitative RT–PCR. To compare the response to these ligands with other type of cells, mononuclear cells obtained from healthy volunteers were stimulated by the same ligands and ELISA was performed for IL–6 and IL–8 production.
HCE–T failed to respond to HKLM, PGN, or LTA–SA. IL–6 and IL–8 detected by ELISA in the supernatants after stimulation remained the same as those in unstimulated ones. However, production of both cytokines was elevated after the stimulation of synthetic lipoproteins, Pam3CSK and FSL–1. These findings were further confirmed at the level of IL–6 and IL–8 mRNA by quantitative RT–PCR. On the other hand, mononuclear cells responded to all kind of TLR2 ligands.
HCE responded to only limited TLR2 ligands compared to mononuclear cells, which responded to all TLR2 ligands. Ocular surface epithelial cells have selective response to TLR2 ligands, and may possess distinct innate immune mechanism from immunocompetent cells.
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