Abstract

DO.18.04

Transplantation of penetrating grafts which consist of multiple-donors determines the alloantigenicity of graft epithelium versus stroma/endothelium

Saban D. R.^1,3, Dana R.^1,2,3
1Schepens Eye Research Institute, ²Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, ³Harvard Medical School, Boston, Massachusetts, USA

Objective: Alloantigenicity is considered to be unequal amongst the disparate tissue layers of a corneal allograft. Currently, it is the graft epithelium which is thought to bear the alloantigenic load of a donor button, in part because it houses the majority of all corneal cells. However, this may not be exactly the case since graft rejection can still ensue despite the transplantation of de-epithelialized grafts, or deep lamellar endothelial grafts. Examples such as these indicate that graft stroma/endothelium also bears significant alloantigenicity. We have therefore developed a novel method to measure the alloantigenicity of graft epithelium versus graft stroma/endothelium in a murine model of orthotopic corneal allo-transplantation.
Methods: This was accomplished by transplanting BALB/c (H-2d) hosts with donor buttons created from C57BL/6 (H-2b) stroma/endothelium reconstituted with C3H/He (H-2k) epithelium. The reverse, C3H/He stroma/endothelium reconstituted with C57BL/6 epithelium, was also transplanted. These were compared to conventional allografts (C3H/He or C57BL/6), as well as isografts (BALB/c). All mouse strains selected for donors and host are fully-mismatched at both class I and class II loci.
Results: Alloantigenicity of donor tissue layers was assessed using mixed lymphocyte reactions, whereby recall T cell responses were measured to stimulation with alloantigen matched to graft epithelium, or stroma/endothelium. Using this system, we found a significant recall T cell response to both graft epithelium and graft stroma/endothelium. This was indicated by increased T cell proliferation, IFN-g secretion, and CD⁴⁺ IFN-g⁺ T cell frequencies over the isografted negative control. We found these observations to be consistent both following the transplantation with grafts consisting of C57BL/6 stroma/endothelium + C3H/He epithelium, and C3H/He stroma/endothelium + C57BL/6 epithelium.
Conclusions: These data clearly demonstrate that in addition to graft epithelium, graft stroma/endothelium lead to T cell priming and thus indicating that it too bears significant alloantigenicity in transplantation.
Grant support: Fight for Sight PD06009 (Saban), NIH/NEI T32-07156 (Saban), NIH/NEI RO1-12963 (Dana)

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