Increased dendritic cell density and altered morphology in allergic conjunctivitis

Abstract

BackgroundCorneal and conjunctival epithelial dendritic cells (DC) have an established role in vernal keratoconjunctivitis, however, their role in more prevalent forms of allergic eye disease remains unclear. This study evaluated corneal and conjunctival epithelial DC density, morphology, and distribution observed using in vivo confocal microscopy (IVCM) in allergic conjunctivitis.MethodsIn this prospective, observational study, 66 participants (mean age 36.6 ± 12.0 years, 56% female): 33 with allergic conjunctivitis and 33 controls were recruited. IVCM was performed at the corneal centre, inferior whorl, corneal periphery, corneal limbus, and temporal bulbar conjunctiva. DC were counted and their morphology was assessed as follows: largest cell body size, presence of dendrites, and presence of long and thick dendrites. Mixed model analysis (DC density) and non-parametric tests (DC morphology) were used.ResultsDC density was higher in allergic participants at all locations (p ≤ 0.01), (corneal centre median (IQR) 21.9 (8.7–50.9) cells/mm2 vs 13.1 (2.8–22.8) cells/mm2; periphery 37.5 (15.6-67.2) cells/mm2 vs 20 (9.4–32.5) cells/mm2; limbus 75 (60-120) cells/mm2 vs 58.1 (44.4–66.2) cells/mm2; conjunctiva 10 (0–54.4) cells/mm2 vs 0.6 (0–5.6) cells/mm2, but not at the inferior whorl 21.9 (6.2–34.4) cells/mm2 vs 12.5 (1.9–37.5) cells/mm2, p = 0.20. At the corneal centre, allergic participants had larger DC bodies (p = 0.02), a higher proportion of DC with dendrites (p = 0.02) and long dendrites (p = 0.003) compared to controls.ConclusionsCorneal and conjunctival DC density was increased, and morphology altered in allergic conjunctivitis. These findings imply that the ocular surface immune response was upregulated and support an increased antigen-capture capacity of DC in allergic conjunctivitis.