Higher Frequencies of Macrophages and IL-12 Expression in the Cornea of Very Young Graft Recipients

Abstract

Purpose : The success rates of corneal allografts are substantially lower in children than in adults. However, the immunologic mechanisms underlying higher failure rates in very young graft recipients are not known. The aim of this study was to investigate the frequencies of macrophages and IL-12 expression levels in the cornea of very young and adult graft recipients after corneal transplantation.

Methods : Allogeneic corneal transplantation was performed in 3.5-week-old (very young) and 10-week-old (adult) BALB/c mice using C57BL/6 donors (n=4). Frequencies of F4/80⁺CD11b⁺ macrophages in the cornea and the IL-12 expressing subset were assessed in graft recipients on days 1 and 3 after transplantation using flow cytometry. Protein levels of IL-12 in the cornea of very young and adult graft recipients were quantified using ELISA.

Results : The frequencies of macrophages were significantly higher in the very young mice compared to adult mice (43.0%±2.35 vs. 29.9%± 1.31, p=0.0028) at day 1 after transplantation. While frequencies of IL-12⁺ macrophages in the cornea increased in both groups after transplantation, very young graft recipients demonstrated a more significant increase (11.6-fold and 23.5-fold increase on days 1 and 3, respectively) compared to adult mice (2.4-fold (p=0.01) and 3.3-fold (p=0.04) increase on days 1 and 3, respectively). Additionally, higher levels of IL-12 were detected in the cornea of very young mice after transplantation as compared to adult graft recipients (p<0.0001)

Conclusions : Our data demonstrate higher infiltration of macrophages and higher IL-12 levels in the cornea of very young graft recipients.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.