Propagation of activated T lymphocytes from endomyocardial biopsy samples of cardiac allografts: influence of the addition of recombinant interleukin-4 to the culture environment

Phenotyping of ex vivo propagated graft-infiltrating cells—A tool to monitor rejection in the early post-operative period

Objective and fast methods to diagnose rejection after organ transplantation are needed. In the present study, the ex vivo propagation technique was evaluated for its ability to detect rejection at two different time-points after experimental heart transplantation. Syngeneic and allogeneic heterotopic heart transplantations were performed using inbred rat strains. After 6 or 15 days, cardiac graft biopsies were put in culture and infiltrating cells isolated by the ex vivo propagation technique. The isolated cells were counted and phenotyped by flow cytometry. In parallel, graft sections were analysed with regard to morphology and the presence of infiltrating cells as determined by immunohistochemical stainings. On day 15 after transplantation, the number of cells possible to isolate through ex vivo propagation reflected the morphological changes of the graft, i.e. considerably more cells were obtained from allogeneic transplants undergoing rejection (1052 +/- 205) than from allogeneic grafts under cyclosporine protection (513 +/- 135; p < 0.05) or from syngeneic grafts (378 +/- 87; p < 0.01). Six days after transplantation the allogeneic grafts were strongly rejected with massive cellular infiltration, still there was no difference between allogeneic and syngeneic grafts as to the number of ex vivo propagated cells. However, the proportion of IL-2-receptor expressing T lymphocytes was increased (15.4 +/- 1.8% vs. 9.5 +/- 1.4%; p < 0.05) and the CD4/CD8 ratio reduced (1.0 +/- 0.1 vs. 2.8 +/- 0.2; p < 0.001) in the allogeneic group as compared with the syngeneic. We conclude that the ex vivo propagation technique can be used to distinguish rejection from non-rejection both early and later after transplantation, provided that not just cell counting but also phenotyping of the graft-infiltrating cells is performed.