Interferon gamma-Positive Natural Killer Cells Contribute to Corneal Allograft Rejection in Young Mice

Abstract

Purpose : Survival rates of corneal allografts in children are much lower than in adults. However, the immunologic mechanisms responsible for the higher graft failure rates in young recipients are not clear. The purpose of this study was to investigate the contribution of natural killer (NK) cells to corneal allograft rejection in young vs. adult graft recipients.

Methods : Allogeneic corneal transplantation was performed using 3.5-week-old and 10-week-old BALB/c mice as recipients and C57BL/6 mice as donors (n=10 per group). Weekly graft examinations were performed until 8 weeks post-transplantation to evaluate graft survival. Infiltration of NK cells (CD45⁺CD3^-CD49b⁺) into the grafts was assessed at day 21 after transplantation using flow cytometry. Draining lymph nodes (dLNs) were examined to evaluate the frequencies of interferon gamma (IFNγ)-positive NK cells and the expression of CD25 surface marker by NK cells in young and adult graft recipients at day 7 after transplantation.

Results : 3.5-week-old mice demonstrated significantly lower survival rates compared to 10-week-old mice at week 8 after transplantation (10% vs. 50%, with median survival of 35 vs. 49 days; P=0.027). The frequencies of NK cells in the cornea were significantly higher in 3.5 compared to 10-week-old mice at day 21 post-transplantation (5.04% vs. 0.280%; P=0.0054). In addition, the frequencies of IFNγ-positive NK cells and the mean fluorescence intensity (MFI) of CD25 expression by NK cells were significantly higher in the dLNs of 3.5 compared to 10-week-old mice at day 7 post-transplantation (17.7% vs. 12.4%; P=0.0042 and MFI=1218 vs. 666; P=0.014, respectively).

Conclusions : Early rejection of corneal allografts in young graft recipients correlates with IFNγ-positive NK cell infiltration to the cornea.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.