Human conjunctival epithelial cells express functional Toll-like receptor 5

Area of Science:

• Immunology
• Ocular Surface Biology
• Microbiology

Background:

• The ocular surface is protected by the conjunctival epithelium.
• Toll-like receptors (TLRs) are crucial in innate immunity, recognizing pathogen-associated molecular patterns.
• Toll-like receptor 5 (TLR5) specifically recognizes bacterial flagellin.

Purpose of the Study:

• To investigate the expression and function of TLR5 in human conjunctival epithelial cells (HCjEC).
• To determine the role of TLR5 in response to flagellins from various bacterial species.

Main Methods:

• RT-PCR and flow cytometry were used to detect TLR5 expression in HCjEC.
• ELISA measured interleukin (IL)-6 and IL-8 protein levels.
• Quantitative RT-PCR assessed mRNA upregulation after flagellin stimulation.
• Immunohistochemistry localized TLR5 protein in the conjunctival epithelium.

Main Results:

• HCjEC expressed TLR5 mRNA and protein.
• Flagellins from Pseudomonas aeruginosa and Serratia marcescens upregulated IL-6 and IL-8 mRNA and protein.
• Flagellins from Salmonella typhimurium and Bacillus subtilis did not induce these responses.
• TLR5 protein was found on the basolateral, not apical, surface of the conjunctival epithelium.

Conclusions:

• Human conjunctival epithelium possesses functional TLR5.
• The basolateral localization of TLR5 suggests flagellin-induced inflammation occurs upon epithelial barrier disruption.
• This finding highlights a mechanism for ocular immune response to pathogenic bacteria.