THE PREVENTION OF GRAFT-VERSUS-HOST DISEASE BY THE SERUM OF LIVER RETRANSPLANTED RATS

The effect of serum from orthotopic liver retransplanted rats (re-OLT serum) on graft-versus-host disease (GVHD) was studied in rats. In the re-transplantation model of rat liver, orthotopic liver transplantati on (OLT) was carried out in the DA (RT1(a)) into PVG (RT1(c)) combinat ion; two days later the DA liver was removed and a new PVG liver impla nted into the same recipient (re-OLT). In the in vivo GVHD model, male PVG rats were sublethally irradiated and injected intravenously with 3 x 10(8) DA or BN (RT1(n)) spleen cells through the penial vein. With in 1 h of the inoculation, rats of the experimental group were injecte d with 1 mi of re-OLT serum taken at postoperative day (POD) 7. Rats i n the control group received 1 mi of normal PVG serum or syngeneic re- OLT serum (PVG-PVG, PVG-PVG). All PVG rats in the control groups died of GVHD within 21 days after the inoculation of DA or BN spleen lympho cytes. However, when the animals were treated with re-OLT serum, 100% (6/6) of the rats survived more than 60 days, following inoculation wi th DA lymphocytes but not with BN lymphocytes. The POD 7 re-OLT serum showed a strong inhibition against DA anti-PVG mixed lymphocyte reacti on (MLR), although re-OLT serum did not contain soluble DA class I ant igens, anti-DA class I or II antibody. The potential GVHD inhibitory f actors in re-OLT serum may be two unique immunosuppressive proteins, w hich have been detected by SDS PAGE and reported previously. We conclu de that re-OLT serum has immunosuppressive factors, which, at least in part, prevented the induction of GVHD in rats.