Purpose: The outcome of corneal transplantation may depend on passenger cells in corneal epithelium and stroma. Their presence in normal corneas is controversial. This study aimed at examining this question and elucidating the still unknown influence of ballistic gene transfer.
Methods: Central 2.5 mm discs of epithelial flatmounts and frozen stromal sections cut parallel to the outer corneal surface were stained for F4/80+ and MHC II+ cells. Corneas were immunohistologically examined in an untreated state and after gene gun treatment using minimalistic immunologically defined gene expression (MIDGE) vector DNA of IL-4 and CTLA4 ( n=6), or untreated/gene-gun-treated donor corneas (C3H mice) were orthotopically grafted into gene-gun-treated eyes (BALB/c mice), and their survival was investigated ( n=8).
Results: Untreated control corneas contained 115.7+/-33.7 F4/80+ and 106.8+/-46.2 MHC II+ cells in the epithelium, and 48.9+/-13.2 versus 7.3+/-5.5 in the stromal layer. Ballistic gene transfer caused migration of F4/80+ cells into the corneal stroma ( P<0.01). Graft survival (27.4+/-16.8 days) was not prolonged by gene gun transfection of donor and recipient corneas but increased significantly to 64+/-28 days ( P<0.01) after treating only the recipient.
Conclusions: A multiplicity of F4/80+ and MHC II+ cells in normal murine corneas diminishes the immune privilege of the eye. Ballistic gene transfer impedes graft survival by triplicating these passenger cells in the stromal layer. However, ballistic transfer of MIDGE vector DNA of IL-4 and CTLA4 markedly improves graft survival when treating only the recipient eye.