Abstract
Purpose::
The ocular surface, composed of corneal and conjunctival epithelial cells, is constantly exposed to microbes. It is reported by many groups that corneal epithelial cells express functional toll-like receptors (TLRs), which play an important role in innate immunity by producing cytokines and antimicrobial peptides upon recognizing microbial-associated molecular patterns (MAMPs). We previously reported that human corneal epithelial cells express toll-like receptor 2 (TLR2), but that they respond to only limited kinds of TLR2 ligands. In this study, we investigated the expression and function of TLR2 in human conjunctival epithelial cells in vitro.
Methods::
Human conjunctival epithelium samples harvested at the time of surgery were immunohistochemically examined for TLR2. Expression of TLR2 in conjunctival epithelial cells was studied by RT-PCR and flow cytometry. The cultured immortalized human conjunctival epithelial cell line (HCjE-T) was stimulated with TLR2 ligands, purified lipoteichoic acid from Staphylococcus aureus (LTA-SA), and synthetic lipoprotein (FSL-1). The HCjE-T was also stimulated with IL-1α as a positive control. The amount of IL-6 and IL-8 in supernatants harvested after twenty-four hours of exposure to these ligands was measured by ELISA. IL-6 and IL8 mRNA expressions of HCjE-T after two hours of exposure to each ligand were examined by quantitative RT-PCR.
Results::
TLR2 was expressed intracellularly in conjunctival epithelial cells. HCjE-T stimulated with LTA-SA and FSL-1 showed increased production and mRNA upregulation of IL-6 and IL-8 by ELISA and quantitative RT-PCR compared to un-stimulated HCjE-T.
Conclusions::
HCjE-T expressed functional TLR2s, and ocular surface epithelium possesses functional TLR2s.
Keywords: conjunctiva • immunomodulation/immunoregulation • inflammation