T-cell-mediated immune responses in alloepithelial rejection after murine keratoepithelioplasty.

Purpose: To evaluate the role of delayed-type hypersensitivity (DTH) and cytotoxic T-lymphocyte (CTL) responses on alloepithelial rejection in a murine keratoepithelioplasty model.
Methods: C3H/He mouse corneal lenticules were grafted around the limbus in BALB/c mice, and alloepithelial rejection was assessed by microscopic evaluation. The relation between rejection scores and DTH or CTL responses to donor antigens was assessed by Spearman correlation analysis. Suppression of DTH responses by induction of anterior chamber-associated immune deviation (ACAID) was used to evaluate the contribution of DTH responses to allograft rejection. CTL responses were evaluated by in vitro and in vivo depletion of CD4+ or CD8+ cells.
Results: DTH responses, which developed 2 weeks postoperatively, correlated significantly with rejection scores (correlation coefficient r = 0.55). ACAID induction by anterior chamber inoculation of C3H/He splenocytes significantly suppressed allospecific DTH responses and alloepithelial rejection. While allospecific CTL responses also developed 2 weeks postoperatively and increased by 4 weeks, CTL responses did not exhibit positive correlation with rejection scores (r = -0.36, P = 0.076). The CTL responses were mediated exclusively by CD8+ cells. Although in vivo depletion of CD8+ cells abolished the induction of CTL responses, it did not prevent allograft rejection. Immunohistochemistry showed infiltration of CD4+ and CD8+ cells into the alloepithelium. Positive staining for interferon gamma but not interleukin 4 further implicated the participation of a DTH response.
Conclusions: Allograft rejection after keratoepithelioplasty appears to be mediated primarily by DTH responses, with CTL responses playing only a minor role perhaps in modifying the development of rejection.