Flow cytometric analysis of graft- and host-specific cell migration after allogeneic small bowel transplantation

Background: After small bowel transplantation (SBT), a two-way traffic of g raft and host lymphocytes is observed. We compared the composition and dist ribution of mobile cells under immunosuppression (FK 506 monotherapy and FK 506 therapy in combination with anti-ICAM-1 monoclonal antibody) with the untreated situation after transplantation and during rejection. Materials a nd Methods: Heterotopic SET was performed in the fully allogeneic BN (RT 1( n)) to LEW (RT1(1)) rat model. Monoclonal antibodies specific for leukocyte subsets and strain-specific MHC I antigens were used to analyze cell migra tion with flow cytometry. Results: After transplantation, predominantly gra ft CD4+ cells were detected in the peripheral blood, spleen, and mesenteric lymph nodes (MLN) of the host. The persistence of these cells was dependen t on whether animals were immunosuppressed or not. After replacement of gra ft lymphocytes in the graft MLN, the majority of host lymphocytes were also CD4+ cells. In the untreated group a greater number of these cells express ed the IL-2 receptor. Under immunosuppression the expression of IL-2 recept or and the proportion of natural killer cells significantly decreased at th e onset of rejection. Conclusions: In the drug-treated as well as in the untreated groups simulta neous exchange migration between graft and host leukocytes was observed. At the onset of rejection, distinct differences between drug-treated and untr eated groups were found in graft MLN. Yet no characteristic changes in cell subsets could be found, correlating with the onset of rejection.