Abstract
Purpose: :
All layers of a corneal allograft are not created equal. Graft epithelium is currently considered to bear the immunogenic load of a donor button, which is in part because it houses the majority of all corneal cells. However, this may not be exactly the case since epithelial rejection and/or replacement with host epithelial cells could diminish its immunogenicity. Thus, we hypothesized that graft stroma/endothelium also contributes significantly to alloimmunogenicity and is thereby important in allosensitization of the host.
Methods: :
To address this, we relied on the orthotopic transplantation of chimeric corneal allografts, whereby C57BL/6 graft stroma/endothelium reconstituted with C3H/He graft epithelium (or vica versa) was placed onto a BALB/c host. Conventional C3H/He or C57BL/6 corneal allografts were placed onto other BALB/c hosts as well. Harvested T cells from host draining lymph nodes were co-cultured with BALB/c, C57BL/6, or C3H/He APC for 5 days. Allosensitization was subsequently measured by T cell proliferation via BrdU incorporation, IFN-γ secretion via ELISA, and CD4+ IFN-γ+ T cell frequencies via FACS analysis.
Results: :
Conventional C57BL/6 allografts replaced with a C3H/He epithelium versus C3H/He stroma/endothelium resulted in higher T cell proliferation to C57BL/6 APC stimulation (increase of 40% versus 13% respectively, over the naïve control). Similarly, levels of culture supernatant IFN-γ to C57BL/6 APC stimulation increased by 22% versus 11% over the naïve control, respectively. Lastly, CD4+ IFN-γ+ T cell frequencies arising from C57BL/6 APC stimulation increased by 60% versus 17% over the naïve control, respectively. Similar data was also obtained throughout to C3H/He APC stimulation, when conventional C3H/He allografts were replaced with C57BL/6 epithelium versus C57BL/6 stroma/endothelium.
Keywords: cornea: basic science • transplantation • antigen presentation/processing