Differences in the rate of donor leucocyte migration between natural and drug-assisted tolerance following rat liver transplantation

Abstract

SUMMARYThe number involved in and the rate of migration of donor leucocytes into the following recipient organs (spleen, thymus, bone marrow, lung and mesenteric lymph nodes) were measured in two rat models of orthotopic liver transplantation (OLT) using donor-specific MHC class I antibodies. The first OLT model is one that does not require immunosuppression in order to achieve tolerance and involved the transplantation of DA (MHC haplotype, RT1 a ) livers into PVG (RT1 c ) recipients. The second model was one that required a 7-day (10 mg/kg) treatment with cyclosporin A (CsA) to achieve tolerance and used DA donors into Lewis (RT1 1 ) recipients. Recipient organs were biopsied on days 3, 20 and 87 following OLT and donor leucocyte migration was quantified by immunohistochemistry and computer densitometry of immunoblots of detergent-solublized tissues in order to resolve both membrane-bound and soluble donor MHC class I antigen. In a separate experiment, spleen biopsies were taken following OLT on days 3 and 15 from the naturally tolerizing OLT model (DA into PVG), treated with and without CsA for 7 days and compared with the (DA into Lewis) model. The initial rate of leucocyte migration between days 3 and 21 following OLT was found to be the most rapid into the spleen, followed by the bone marrow and mesenteric lymph nodes in the naturally tolerant (DA into PVG) model when compared with the (DA into Lewis) model. The number of donor leucocytes in the spleen and mesenteric lymph nodes in both models was, however, approximately the same by 87 days. No real difference in the rate of leucocyte migration was seen in the thymus or the lung for both transplant models over the time course assayed. CsA was found to lower the rate of donor leucocyte migration only over the period it was administered. The rate of donor leucocyte migration into the spleen was still much lower 15 days after OLT in the (DA into Lewis) model compared with the (DA into PVG) model treated with and without CsA. Thus the differences in the rate of donor leucocyte migration into the spleen, bone marrow and mesenteric lymph nodes immediately following OLT may offer an explanation as to why the (DA into PVG) combination is able to accept a transplanted liver without immunosuppressive therapy.

Identification of two down-regulated genes in rat liver allografts by mRNA differential display

“…D A livers were orthotopically transplanted into D A (n = 18), PVG (n = 18), and LEW (n = 18) recipients. As reported previously [11], OLT (DA-PVG) rats naturally overcome rejection while all OLT (DA-LEW) rats die from acute rejection within 14 days. Syngeneic OLT (DA-DA) rats were used as controls since no rejection occurs and rejection-related factors are eliminated.…”

PEAK PROTEIN EXPRESSION OF IL-2 AND IFN-γ CORRELATE WITH THE PEAK REJECTION EPISODE IN a SPONTANEOUSLY TOLERANT MODEL OF RAT LIVER TRANSPLANTATION

“…Further experiments from the same group of investigators, and in the same transplant combinations, subsequently demonstrated that higher levels of IL-2 and IFN-mRNA were found in celiac lymph nodes and spleen in the spontaneously tolerant combination of (LEW-DA) when compared with the converse rejector combination (DA-LEW). 1,15 When considering the phenomenon of microchimerism on the transplant process 1,[4][5][6]15,23 it is difficult to understand why higher levels of IL-2 and IFN-would be found only in lymphoid organs and not similarly increasing in the transplanted liver. The observed paradoxical immune activation in the lymphoid tissues of tolerant animals has been suggested to be associated with a high-dose tolerance mechanism.…”

“…Immunosuppressive therapy using drugs such as cyclosporin A (CsA) or FK506 are not required for orthotopic liver transplantation (OLT) between the inbred rat strains DA (MHC haplotype RT1 a ) and PVG (RT1 c ) to achieve allograft tolerance. [1][2][3][4][5][6] Animals transplanted in this combination, despite a complete major histocompatibility complex (MHC) mismatch, do not reject the transplanted allograft and many mechanisms have been proposed to account for this phenomenon. These have included the presence of unusual soluble MHC class I molecules synthesised by the liver, [7][8][9] presence of anti-MHC class I antibodies, 4,10-12 a higher rate of donor cell migration, 5,6 expression of novel immunosuppressive proteins 13, 14 and possible high-dose-activation-associated tolerance.…”

“…The peak rejection episode in the spontaneous tolerant OLT model of DA (donors) into PVG (recipients) is between 10 and 14 days 21 as it is also for (Lewis into DA) and (DA into Lewis). 5,19,22 In order to clarify this further we have under taken measurements of the cytokines IL-2, IFN-and TNF-both prior to, during and post rejection episode. In each case the presence of both the cytokine protein product and mRNA was examined via immunoblotting assays and by reverse transcriptase polymerase chain reaction (RT-PCR) for IL-2 and IFN-mRNA.…”

Immunological role of indoleamine 2,3‐dioxygenase in rat liver allograft rejection and tolerance

“…37 DA livers were orthotopically transplanted into DA, PVG or LEW recipients. As reported previously, 38 OLT (DA-PVG) rats naturally overcome rejection without using any type of immunosuppressants (spontaneous tolerance model). In contrast, all OLT (DA-LEW) rats die from acute rejection within 14 days (acute rejection model).…”