Administration of exogenous interleukin-2 abrogates spontaneous rat liver allograft acceptance but does not affect long-term established graft survival
Delrivière, L.; Havaux, X.; Latinne, D.; Bazin, H.; Kamada, N.; Nordlinger, B.; Gianello, P.
Transplantation 63(11): 1698-1701
1997
ISSN/ISBN: 0041-1337 PMID: 9197371 Document Number: 469714
Background. Spontaneous tolerance to the orthotopic liver allograft uniformly occurs in the DA (RT1-a) to PVG (RT1-c) rat combination despite a fully allogeneic barrier. Methods. To assess whether spontaneous acceptance might be the consequence of a T cell help deficit at the time of the first exposure of alloantigens to the host, we studied the effect of exogenous interleukin (IL)-2 injections at the time of liver transplantation and during long-term follow-up. Results. Although spontaneous acceptance of the liver allograft constantly ensued in the DA to PVG combination, a daily injection of recombinant IL-2 (3 times 10-5 U) uniformly provoked acute cellular rejection of the liver allograft and consequently the death of animals by postoperative day 5-6. Simultaneous to the graft loss, hepatic enzymes (alanine aminotransferase) increased more than 50-fold in IL-2-treated recipients, whereas similar IL-2 treatment did not produce any hepatic dysfunction in syngeneic animals. By immunohistology, the expression of the a chain of the IL-2 receptor, usually undetectable in untreated animals, was evident on CD4 and CD8 lymphocytes infiltrating the liver graft. In contrast, a similar IL-2 regimen and even higher IL-2 doses (1 times 10-6 U) did not abrogate the liver allograft survival during long-term follow-up. Conclusions. Our results demonstrate that spontaneous rat liver allograft acceptance may be abolished by exogenous IL-2 injections, which suggests that an "inherent T cell help deficit" might be implicated in the spontaneous acceptance mechanisms of DA to PVG liver allografts.