Modulation of epithelial immunity by mucosal fluid.

Area of Science:

• Immunology
• Microbiology
• Ophthalmology

Background:

• Mucosal epithelial cells, including the ocular surface, possess innate resistance to microbes in vivo.
• However, their susceptibility to microbial virulence in vitro suggests additional defense mechanisms are at play.
• While mucosal fluids contain antimicrobials, pathogenic microbes can still thrive, indicating a need for further investigation into epithelial resistance.

Purpose of the Study:

• To investigate the direct role of tear fluid in enhancing epithelial cell resistance to bacterial invasion and cytotoxicity.
• To identify the molecular mechanisms by which tears modulate epithelial cell defense pathways.

Main Methods:

• Tear fluid was applied to ocular surface epithelial cells.
• Activation of transcription factors NFκB and AP-1 in response to bacterial antigens was measured.
• Differential gene expression in epithelial cells treated with tears was analyzed.
• siRNA knockdown was used to assess the role of specific genes (RNase7, ST-2) in bacterial invasion resistance.

Main Results:

• Tear fluid directly enhanced epithelial cell resistance to bacterial invasion and cytotoxicity.
• This enhanced resistance correlated with tear fluid-magnified activation of NFκB and AP-1 transcription factors.
• Tears differentially regulated the expression of epithelial cell defense genes.
• Knockdown of RNase7 and ST-2 diminished the protective effect of tears against bacterial invasion.

Conclusions:

• Tear fluid plays a crucial role in modulating ocular surface epithelial immunity.
• Tears enhance epithelial cell defense by priming innate immune pathways, leading to increased resistance to bacterial threats.
• This study highlights a novel role for mucosal fluids in bolstering epithelial defense beyond direct antimicrobial effects.