Abstract
Purpose: :
The purpose of this study was to evaluate the phenotypic dynamics of bone marrow (BM) cells in corneal grafts, cervical lymph nodes (LNs) and spleen after corneal transplantation in GFP+–bone marrow chimeric mice.
Methods: :
Adult C57BL/6 mice received 11 Gy of irradiation while using a lead eye protector, and were injected with 1 ×107 bone marrow cells prepared from EGFP transgenic mice (C57BL/6 background) through the tail vein. At 6 weeks after GFP+–syngeneic bone marrow transplantation, orthotopic corneal transplantation was performed using normal corneas of allogeneic BALB/c and syngeneic C57BL/6 donors. After corneal transplantation, GFP+ cells in whole–mount cornea were assessed immunohistochemically using confocal microscopy to evaluate phenotypes, density and distributions. Flow cytometry was used to analyse the GFP+ cells in the LNs and Spleen of these recipients.
Results: :
Expressions of CD11b and CD11c on GFP+ cells in LNs and spleen were up–regulated, and costimulatory molecules such as CD40, CD80 and CD86 on these cells were up–regulated after corneal transplantation. However, no differences were identified between syngeneic and allogeneic transplantations at 24 h. At 1 week, expression of CD11c and costimulatory molecules on GFP+ cells in LNs in allograft–bearing recipients were markedly up–regulated compared to syngeneic graft–bearing recipients. Expression of these molecules returned to the same levels as naïve mice by 8 weeks. Densities of costimulatory molecule–expressing CD11c– or CD11b–positive cells in corneal grafts increased, although no differences were seen between allografts and syngeneic grafts until 1 week after corneal transplantation. Numbers of costimulatory molecule–expressing CD11c– or CD11b–positive cells markedly increased in allografts at 2 weeks, and these cells occupied the rejected allografts long after 8 weeks.
Conclusions: :
Phenotypic analysis of BM cells in corneal grafts, LNs and spleen after corneal transplantation in GFP+ BM chimeric mice demonstrates that BM cells in LNs, spleen and corneal grafts are activated at an early period after corneal transplantation, irrespective of alloantigens presence. BM cells in LNs subsequently play an important role in antigen–specific immune responses. Activated BM cells keep accumulating into rejected allografts, even after BM cells are no longer activated in LNs. These BM cells in rejected allografts may function in tissue repair, rather than allo–specific immune response.
Keywords: immunomodulation/immunoregulation • transplantation • antigen presentation/processing