Characterization of dendritic cell phenotype in allergic conjunctiva: increased expression of FcεRI, the high-affinity receptor for immunoglobulin E

Purpose Dendritic cells (DCs) express the high-affinity receptor for IgE (Fc epsilon RI) on their surface, which may enhance their ability to capture and internalize antigens for presentation to T-lymphocytes. The aim of this study was to determine if expression of Fc epsilon RI(+) DCs is increased in the conjunctivae of vernal keratoconjunctivitis (VKC) patients compared with those of normal controls. Methods Conjunctival biopsies were obtained from non-atopic and VKC patients. Double immunohistochemical staining was carried out using antibodies against Fc epsilon RI and the CD1a antigen, a DC marker. The double-positive cells were counted in five representative fields of view for each conjunctival sample. Results Fc epsilon RI(+) CD1a(+) cells were present in significantly higher numbers in VKC conjunctivae compared with normal controls (mean cell count of 21.3 in VKC vs 5.0 in controls, P<0.005). In normal patients the Fc epsilon RI-expressing DCs tended to be confined to the epithelial layer or the superficial substantia propria, but in the VKC samples these Fc epsilon RI(+) cells were mainly concentrated in the deeper substantia propria. Conclusions Fc epsilon RI(+) DC numbers are elevated in the conjunctivae of VKC patients, a finding consistent with the results of other studies focusing on atopic conditions. Elevated expression of Fc epsilon RI on DCs would facilitate antigen presentation and enhance T-cell priming, thereby contributing to ocular symptoms. Eye (2009) 23, 2099-2104; doi:10.1038/eye.2008.372; published online 19 December 2008