A decrease in the density of HLA-DR-positive cells occurs faster in corneas stored in organ culture than under hypothermic conditions.

Aims: To compare the number of antigen-presenting cells (APC) at various locations in fresh human corneoscleral disks and in those that are stored for grafting under hypothermic conditions or in organ culture (OC) with the aim of determining the conditions under which the decline in APC numbers is most substantial.

Methods: Cryosections obtained from fresh corneoscleral disks and disks stored under hypothermic (Optisol-GS) or OC conditions were used. The density of HLA-DR-positive cells was determined on cross sections using enzyme immunohistochemistry (alkaline phosphatase-antialkaline phosphatase technique). Longitudinal sections were used for detecting ATPase activity.

Results: The densities of HLA-DR-positive cells in both the epithelium and stroma increased from the central (3.79 and 0.61/mm(2)) to the peripheral cornea (5.56 and 1.35/mm(2)) as well as to the limbus and conjunctiva. A marked decrease in the number of HLA-DR-positive cells occurred after 7 days of storage in all corneal areas, the limbus and conjunctiva, compared to fresh tissue. No positive cells were found in the epithelium of corneas after 14 days in OC and after 21 days in hypothermic storage. Twenty-eight days of storage in OC led to the complete absence of HLA-DR-positive cells in the epithelium of the limbus and conjunctiva, and to a significant reduction in the stroma.

Conclusion: Corneas stored in OC longer than 14 days are likely to be less immunogenic than corneas stored under hypothermic conditions, thus resulting in a possible positive effect on prolonging graft survival.