Abstract
Purpose: :
Inflammation in AC occurs mostly in the conjunctiva, but is only thought to significantly involve the cornea in advance forms (e.g. allergic keratoconjunctivitis). We investigated IC infiltration of the cornea in experimental AC.
Methods: :
AC was induced in C57BL/6 mice via immunization with ovalbumin (OVA; 100µg)/pertussis toxin (300ng)/alum (1mg), and challenged with OVA (250 ug) eye drops once daily for 7 days. Non-immunized control mice were similarly challenged. Periocular skin signs, mucoid discharge, corneal erosions, conjunctiva scarring, cataract, or papillae are absent in all groups. Likewise, challenged corneas remain transparent in this model. Standardized slit lamp scoring of AC clinical signs (chemosis, redness, tearing, lid edema) was performed in a masked fashion. Heidelberg Retina Tomograph III (HRT) scans were performed throughout. Immunofluorescence on whole-mount preprations were examined with confocal microscopy. Experiments (n>3) were repeated at least twice.
Results: :
Increased AC clinical scores (p<0.05) began on challenge day 3 in immunized mice (5.5±0.45) relative to non-immunized controls (3.5±0.45 naive). HRT analysis showed an IC increase (p<0.05) in superior temporal bulbar conjunctivae of immunized mice (531±50 cells/mm2) relative to controls (117±115 cells/mm2) on challenge day 2. IC increase (p<0.05) in temporal cornea regions of immunized mice (220±25 cells/mm2) relative to controls (86±6 cells/mm2) began on challenge day 2. IC increase (p<0.05) in nasal cornea regions in immunized mice (407±21 cells/mm2) relative to controls (0±0 cells/mm2) began on challenge day 3, and in the central cornea in immunized mice (62±6 cells/mm2) relative to controls (23±2 cells/mm2) began on challenge day 4. Confocal microscopy inidcated that mononuclear cells in the conjunctiva and cornea similarly included monocytes (CD11b+/F480+/Gr1+) and macrophages (CD11b+/F480+/Gr1-) and few dendritic cells (CD11c+).
Conclusions: :
HRT allows visualization, mapping, and quantitation of IC in both conjunctiva and cornea in experimental AC. Significant IC infiltration occurs throughout the cornea and the kinetics of their recruitment is associated with development of AC clinical signs. Our novel identification of IC in the cornea may represent a newly appreciated and important component in the pathology of AC pathology.
Keywords: conjunctivitis • inflammation • immunomodulation/immunoregulation