The Number of HLA–DR–Positive Cells Decreased Faster in Corneas Stored in Tissue Culture than Under Hypothermic Conditions

Abstract

Purpose: : The aim of this study was to compare the number of HLA–DR–positive cells in fresh corneo–scleral discs and in discs stored under hypothermic or tissue culture (TC) conditions.

Methods: : Six fresh and four stored human corneo–scleral discs were used. Corneas were maintained under hypothermic or TC conditions for 3–5, 7–9, 12–14 or 21–24 days. The discs were dissected into four concentric zones: central (0–4mm), pericentral (4–7mm), and peripheral cornea (7–12mm), and the limbo–scleral (>12mm) area. Indirect immunohistochemistry using an anti–HLA–DR monoclonal antibody (Dako, 1:200) was performed on 7 µm thick cryosections. HLA–DR–positive cells/mm² were counted using a Lucia image analysis system.

Results: : The numbers of HLA–DR–positive cells in fresh tissue were 2.6 and 0.8 cells/mm² in the epithelium and stroma of the central cornea, 3.8 and 1.0 cells/ mm² in the pericentral cornea, and 5.7 and 1.7 cells/mm2 in the peripheral cornea. At the limbus we found 19.0 and 39.5 cells/mm² in the epithelium and stroma, respectively, and in the conjunctiva 29.4 and 43.0 cells/mm². Less than 0.2 HLA–DR–positive cells/mm² were detected in the central and pericentral areas after 7–9 days in TC and after 12–14 days under hypothermic conditions.

Conclusions: : The pronounced decrease observed in the number of HLA–DR–positive cells, extending even to their complete absence, during cultivation periods usually used for TC storage makes corneas stored in TC preferable from the point of view of preventing corneal graft rejection compared to those maintained in hypothermic storage, where the decrease in the number of HLA–DR–positive cells at storage times normally used prior to grafting is not significant.

Keywords: antigen presentation/processing • cornea: epithelium • cornea: storage