Expression of Toll-like Receptors in Healthy and Allergic Conjunctiva

Abstract

To investigate the expression of toll-like receptors (TLRs) in healthy and active vernal keratoconjunctivitis (VKC) conjunctiva. Comparative nonrandomized interventional study. Nine patients with vernal keratoconjunctivitis and 10 healthy subjects. Normal and VKC conjunctiva were evaluated for TLR-2, TLR-4, and TLR-9 mRNA and proteins by relative real-time polymerase chain reaction and immunohistochemistry. Colocalization of TLRs was further evaluated by confocal microscopy and double-labeled immunofluorescence in T cells (CD4), mast cells (AA1), and eosinophils (EG2). Identification of TLRs at molecular and biochemical levels and identification of inflammatory cells that coexpress these receptors. Toll-like receptor 2, TLR-4, and TLR-9 were expressed in normal and VKC conjunctival epithelium and stroma, both with a more intense immunoreactivity in the stroma. In VKC tissues, TLR-4 was upregulated, TLR-9 was downregulated, and TLR-2 was slightly decreased relative to normal tissues. Toll-like receptor 4 was localized on CD4+ lymphocytes, eosinophils, and mast cells, whereas lymphocytes and eosinophils, but not mast cells, expressed TLR-9. Toll-like receptors are expressed in healthy and allergic conjunctiva. The upregulation or downregulation of these receptors and their presence on inflammatory cells suggest a role of TLRs in VKC.