An essential role for dendritic cells in vernal keratoconjunctivitis: analysis by laser scanning confocal microscopy
CD4+ T helper type 2 cells play a central role in the pathogenesis of vernal keratoconjunctivitis (VKC), and antigen-presenting cells are required for the cell activation. In this study, we aimed to survey the density, distribution, and morphology of dendritic cells (DCs) in patients with VKC by in vivo confocal microscopy.
Thirty-five patients (mean, 12.4 ± 5.3 years) affected by VKC were included. All patients were treated with 0.1% fluorometholone eye drops and 0.5% cyclosporine A eye drops. The density and morphological and distributional characteristics of DCs in each right eye were evaluated by in vivo confocal microscopy before treatment and at 1, 3, and 6 months after treatment. Thirty-five age-matched normal subjects (mean, 16.5 ± 1.8 years) were studied as controls.
There was significant difference in age between the VKC group and the control group (F = 18.17, P < 0.05). Compared with normal eyes, increased numbers of DCs were found in patients with VKC, with mean cell densities of 244.09 ± 59.76 cells/mm2 at the bulbar conjunctiva, 574.53 ± 87.34 cells/mm2 at the limbus, and 403.32 ± 106.59 cells/mm2 at the peripheral cornea before treatment. These DCs exhibited a typical dendritic shape. At 3 months after treatment, the DC density at the conjunctiva decreased significantly (P < 0.05), approximating that in the controls. At 3 and 6 months, the DC densities at the limbus and peripheral cornea also decreased significantly (P < 0.05), but were still statistically higher than those in the controls. These DCs, with small dendritic processes or irregular shapes, were observed to gradually locate at the epithelial basal membrane and subbasal nerve plexus.
In vivo confocal microscopy appears to be a valuable tool in evaluating the dynamic change of DCs at the conjunctiva and cornea. DCs play an essential role in VKC and therefore may constitute a target for therapeutic intervention for VKC.