Purpose
This study evaluated effects of cholinergic stimulation on mucin binding and antigen migration through conjunctival goblet cells (GCs).
Methods
Experiments were performed without and with pre-topical stimulation of mucin secretion by the cholinergic agonist carbachol in female B6 mice. OVA Alexafluor-594 (45kDA) or labeled Dextran (10kDA or 70kDA) was applied topically and cornea and forniceal conjunctiva were harvested after 30 minutes and stained for either MUC2 or MUC5AC with an immunofluorescent technique. Whole epithelial and stroma thickness digital confocal images were captured with a laser scanning confocal microscope using the Z-stack option to evaluate OVA and Dextran distribution on the ocular surface and stroma and mucin binding.
Results
During homeostatic conditions both antigens diffused into the stroma, but the pattern was different. Dextran was found in clusters while OVA was diffusely distributed. Goblet cells mucins bound topically applied antigens and goblet cells provided conduits for antigen passage into the stroma (Figure). There was greater migration of 10kDA dextran through goblet cells than 70kDA dextran. Pre-cholinergic stimulation with carbachol 20 minutes prior to topically applying antigens increased mucin binding on the ocular surface and decreased diffusion into the stroma at 30 minutes.
Conclusions
This study confirmed that goblet cell mucins bind topically applied antigens and goblet cells serve as conduits for antigen passage to the conjunctival stroma. Cholinergic stimulation results in greater antigen trapping by mucins on the ocular surface and limits diffusion into the stroma.