B-Zellen des Spenders in den Follikeln der Milzen experimenteller Lungentransplantatempfänger

Abstract

After transplantation of vascularized organs, passenger leukocytes of donor origin move to secondary lymphoid organs of the recipient and to other parts of the body. On the one hand, these cells, appear to play a pivotal role in the initiation of allograft rejection. On the other hand, it has been suggested that pronounced recipient chimerism is not only a hallmark of allograft tolerance but might also be involved in tolerance induction. Orthotopic transplantation of the left lung was performed in the Dark Agouti to Lewis rat strain combination. These lungs are irreversibly rejected between days 4 and 6 posttransplantation. Graft recipients were sacrificed at intervals of 24 h from days 1 to 6 after transplantation and the spleens were either fixed for paraffin histology or snap frozen for cryostat sections. For comparison, spleens from renal allograft recipients transplanted in the same rat strain combination were analyzed. MHC class II antigens of the donor rat strain were detected by monoclonal antibody OX-76. In double-staining experiments, using OX-76 as well as antibodies to cell surface antigens characteristic for different leukocyte subpopulations, we identified the micro-anatomical localization as well as the identity of these OX-76-positive cells. MHC class II-positive cells of donor origin were already detected on day 1 posttransplantation. They rapidly increased in number until day 3, decreased thereafter and were no longer detectable on day 6. Donor-derived spleen cells were relatively large and star-shaped. Most of the OX-76-positive cells were localized in splenic follicles. These cells expressed the B cell variant of CD45R detected by monoclonal antibody OX-33 and exhibited weak acidic phophatase activity. All cell surface antigens typical for macrophages, dendritic cells, follicular dendritic cells, NK cells and T lymphocytes were not detected. In the spleen of renal allograft recipients, only few donor-derived cells were seen. In conclusion, after lung transplantation, numerous MHC class II-positive donor-derived B cells migrate to the splenic follicles of the recipient. We speculate that these cells might in part be responsible for the immunological differences described among renal and pulmonary allografts.