Effect of leflunomide and cyclosporine on graft survival and changes in lymphocyte phenotypes in a rat heart allotransplantation model.

Cyclosporine-A (CSA) and leflunomide (LF) can delay or prevent organ graft rejection. We investigated the combination of LF, CSA and splenectomy on graft survival and changes in lymphocyte phenotypes (LP) in a rat allotransplantation model. In the study 19 Lewis rats were splenectomized prior to heterotopic heart transplantation. SPRD rats served as donors. The recipients were divided into three groups: A--five animals received CSA and LF for two weeks, B--five received intermittent CSA and LF for the whole investigation period and C--nine received no drug therapy. LP was quantified relatively by flow cytometric analysis. We found that graft survival was longer in group A (median 155 days, range 52-348) and B (341, range 338-342), compared to group C (8, range 7-13). The histological examination, however, revealed signs of rejection in all allografts. In group A all except one animal and in group C the morphological changes were characterized by severe acute rejection. In contrast, one animal in group A and all the animals in group B revealed signs of moderate acute rejection and in most animals signs of chronic rejection were also found. The reduction of Pan-T and CD4+ cells in group B compared to the control group was associated with no clinical rejection, while the increase of CD8+ cells in group C and partly in group A (except for animal 3) was associated with clinical rejection. No difference in LP was detected between groups A and B in the study period. We concluded that a combination of CSA, LF and splenectomy was efficient in preventing clinical rejection, however, there were signs of rejection morphologically even in animals without clinical rejection. The changes in LP over time could not predict the clinical outcome. However, increase in CD8+ cells was highly associated to clinical rejection among nonimmunosuppresed animals.