Abstract
Abstract: :
Purpose: To determine the phenotype and distribution of antigen presenting cells (APCs) at 6 months after transplantation, in the posterior surface of the corneal allografts and in spleen of the recipients bearing long-term accepted or rejected corneal allografts. Methods: Normal corneas of C57BL/6 mice were transplanted orthotopically into normal eyes of BALB/c mice. Graft survival was assessed clinically. Cornea and spleen were harvested from normal BALB/c mice, recipients bearing accepted allografts (acceptors) or rejected allografts (rejecters), at 6 months. Contents of CD11c, CD11b, CD1d, CD40, CD80, CD86, and MHC class II (I-Ad) positive cells in the posterior surface of the whole mount corneas and in spleen cells were analyzed by confocal microscopy and flow cytometry, respectively. Results: CD11c, CD1d, or CD11b positive cells were not found in the posterior surface of normal cornea. The posterior surface of the accepted allografts retained corneal endothelium with normal appearance, and contained a few cells in which both CD11c and CD1d are positive (i.e. dendritic cells, DCs), or CD11b is positive (i.e. macrophages). These cells expressed none of activation markers (CD40, CD80 or CD86), reflecting an immature phenotype. On the other hands, the posterior surface of the rejected allografts was devoid of corneal endothelium and was covered with DCs and macrophages. Expression of I-Ad, CD40, CD80 and CD86 in these cells was enhanced. In the rejecter spleen, the population of macrophages was about two times more than those of naive or acceptor, and expression of I-Ad, CD40 and CD86 in DCs and macrophages was enhanced. In the acceptor spleen, CD11c negative CD1d positive cells (i.e. marginal zone B cells) increased, whereas, these cells remarkably decreased in the rejector. Conclusion: Even at post-grafting 6 months, the rejecter contained a high distribution of mature DCs and macrophages in the graft and spleen. It is indicated that a few number of immature APCs in the graft and marginal zone B cells in spleen have a role in long-term graft survival.
Keywords: immune tolerance/privilege • transplantation • antigen presentation/processing