Protection of heart and rejection of lymphocyte allografts from the same donor in recipients of donor-specific transfusions.

Organ allografts survive in hosts treated with immunosuppressive drugs. The question arises as to whether cells isolated from organ or tissue of an allogeneic donor and transplanted to a genetically disparate recipient can also benefit from the immunosuppressive regimen. We reported previously that the DST (donor specific transfusion) recipients accept heart allografts but reject hyperacutely i.v. infused lymphocytes from the same as DST donor. The present study was devoted to elucidation of the mechanism of these divergent processes. Syngeneic BN hearts and mesenteric lymph node lymphocytes were transplanted to LEW rats pretreated one week previously with donor specific blood transfusions. The allogeneic BN lymphocytes transplanted i.v. to LEW rats receiving one BN DST were rejected hyperacutely within 6 hrs, whereas BN heart grafts transplanted to the BN DST-treated LEW recipients survived 14 +/- 2 days. Adoptive transfer of LEW anti-BN DST sera to naive LEW rats caused destruction of the transplanted BN lymphocytes. The LEW BN DST recipients possessed IgG and IgM class alloantibodies binding to BN lymphocytes and heart endothelial cells. mAbs against MHC class I (OX18) and class II (OX6) antigens neither blocked binding of antibodies of DST-recipient sera to BN lymphocytes nor protected the preincubated BN lymphocytes against destruction after transplantation. Western blot analysis revealed that alloantibodies from DST-recipient sera bound strongly to BN lymphocyte membrane proteins of 60 kd m.w. but not to 45 kd and 30 kd MHC class I and II proteins. Taken together, DST has no protective effect on intravenously transplanted cells. In contrast, it accelerates the rejection. Alloantibodies present in DST-recipient sera "shield" antigens on the surface of organ allograft endothelial cells, thereby protecting them from recognition and cytotoxic effect. Simultaneously, these alloantibodies "opsonize" the intravenously transplanted lymphocytes and facilitate their halting in lymphoid organs and subsequent lysis. Antibodies other than those directed against MHC seem to mediate both these processes. The results of these studies provide also evidence that the effector mechanism of rejection may be different depending on location of the graft, in the lymphoid as in case of transplanted lymphocytes or in non-lymphoid tissues as heart grafts.

Hepatocyte transplantation--granulocytes and mononuclear cells recognize the surface of isolated autologous hepatocytes as non-self and destroy them.

Successful transplantation of hepatocytes (HC) is hampered by lack of a proper cellular (stromal) and humoral (cytokines) environment at the site of implantation. We have found that another factor responsible for the low survival rate of transplanted HC is their rapid destruction by host granulocytes. In this study we have investigated the mechanism of the rapid elimination of transplanted hepatocytes in a syngeneic and allogeneic recipient. Only 10% of the radioactivity of syngeneic (LEW-LEW) or allogeneic (BN-LEW) HC was recovered in recipient lymphoid tissues 6 h after i.v. infusion. Pretreatment of the recipient with Endoxan or sublethal irradiation brought about an increased accumulation of HC radioactivity in lungs and spleen, indicating the entrament of live cells in these organs. Only a few HC could be seen in the liver 6 h after intraportal infusion. Granulocytes were found to be cytotoxic to HC in vitro (39%). Monoclonal antibodies to class I and II antigens, CD 11/18 and 54, did not block the granulocyte cytotoxicity. Granulocyte and HC cluster formation could be seen on smears from a drop of mixed cultures, the rates of formation increasing with the time of incubation. Two out of 34 monoclonal antibodies to HC surface molecules partly blocked the granulocyte cytotoxicity. No evident differences in the elimination rate and in in vitro cytotoxicity were seen between the syngeneic and allogeneic HC.

Liver sinusoidal passenger lymphocytes reveal suppressive properties and prolong allograft survival.

Liver sinusoidal washout cells are low responders to mitogens, and suppressive in autologous PBM, and portal blood mononuclear cells, PHA supplemented, and autologous mixed lymphocyte cultures. They are less immunogenic after IV administration into allogeneic recipients than PBM, which could be measured in an in vivo allogeneic lymphocyte elimination test. The level of immunization is strain dependent. In the BN to LEW combination, they are more immunogenic than in the LEW to DA pairs. This parallels heart allograft survival times, which were longer in LEW to DA than BN to LEW combinations.

Liver sinusoidal washout cells transferred to allogeneic recipients reveal tolerogenic properties.

Liver sinusoidal washout cells, containing a large fraction of LGL cytotoxic to tumor cell lines in vitro, are less responsive to mitogens and suppress the responsiveness of autologous and third-party PBM to mitogens and autologous mixed lymphocyte culture, compared with autologous portal vein or PBM. They are less immunogenic after IV administration into allogeneic recipients, which can be observed in an in vivo allogeneic lymphocyte cytotoxicity test. Immunization of allogeneic recipients with liver sinusoidal washout cells slightly prolongs heart allograft survival time.

Donor-specific transfusion does not mitigate but accelerates rejection of intravenously transplanted lymphocytes.

Rat allogeneic heart or kidney grafts are rejected within 6 to 8 days, whereas lymphoid cells from the same donor transplanted intravenously across the MHC barrier are eliminated, in most part, within 6 h. We have found that donor specific transfusions (DST) significantly prolonged the survival time of organ allograft but accelerated destruction of i.v. transplanted lymphocytes. Partial elimination of transplanted lymphocytes was observed after third-party blood transfusion. Blocking of the MHC class I and II determinants on transplanted lymphocytes with monoclonal antibodies OX18 and OX6 did not have effect on the lymphocyte elimination kinetics. The effect of hyperacute elimination of allogeneic lymphocytes by DST-treated rats could be adoptively transferred with their sera, although the cytotoxic antibody titer against donor MHC antigens was in these sera low or hardly detectable. DST-recipient sera contained donor-specific IgG and IgM alloantibodies. It seems that these "enhancing" antibodies could block the MHC products on organ graft endothelial cells, thereby preventing attack of circulating donor-specific cytotoxic lymphocytes. At the same time they may opsonize the transplanted lymphocytes, thereby facilitating their recognition and removal in the lymphoid organs of graft recipient.