Th2-biased immune system promotion of allogeneic corneal epithelial cell survival after orthotopic limbal transplantation

PURPOSE: The Th2-biased immune system can promote penetrating keratoplasty survival in mice. A series of experiments were performed to determine whether this system could prolong corneal limbal transplant (LT) survival. METHODS: BALB/c (H-2d) mice were immunized with 50 microg of keyhole limpet hemocyanin (KLH) in incomplete Freud's adjuvant. Four weeks later, the corneal epithelium, including the limbal area, was removed, and the mice received LT from B10.D2 (H-2d), C57BL/10 (H-2b), or enhanced green fluorescence protein (EGFP) transgenic (H-2b) donor mice. Immediately thereafter, recipient mice were immunized with 50 micro g of KLH or Hanks' balanced salt solution (HBSS; control) in complete Freund's adjuvant. The allograft fates were assessed clinically. Lymphocytes of recipients were examined for donor-specific proliferation and for donor-specific cytokine production in vitro. RESULT: The regenerated epithelia of all C57BL/10 (n=14) and B10.D2 (n=18) grafts were rejected swiftly in control mice, whereas 66.6% of C57BL/10 grafts (8/12, P<0.001) and 62.8% of B10.D2 grafts (22/35, P<0.001) in the KLH immune group remained significantly clear for 8 weeks. Moreover, EGFP donor epithelial cells were detected from the healthy corneas of KLH-immunized mice. As for the in vitro assay, at 1 week after B10.D2 grafting, lymphocytes from KLH-immunized groups showed neither proliferation nor increased cytokine secretion. CONCLUSIONS: The Th2-biased immune system can support LT prolongation irrespective of donor disparity and can suppress corneal neovascularization. This prolongation is not due to induction of donor-specific regulatory cells, but is presumably at least associated with the suppression of allosensitization.