Intestinal graft versus native liver cytokine expression in a rat model of intestinal transplantation: Effect of donor-specific cell augmentation

Introduction Immunomodulation by portal vein delivery of donor antigen reduces intestinal graft rejection. We investigated the impact of portal venous donor-specific cell augmentation (blood versus bone marrow) on cytokine expression in intestinal grafts versus native livers. Methods Ten groups of intestinal transplants (brown Norway male to Lewis female rats) varied by (1) the type of donor-specific cell augmentation and (2) the use and dose of tacrolimus-based immunosuppression. Tissue samples for histologic analysis and cytokine mRNA analysis were obtained at designated time points. Results Without immunosuppression, no type of cell augmentation reduced the rate of rejection. With immunosuppression, outcome was significantly better after portal donor-specific blood transfusion (versus bone marrow infusion). Irrespective of the type of cell augmentation, severe rejection caused strong intragraft expression of IL-1α, IL-1β, IFN-γ, and TNF-α; liver expression mainly involved TNF-α. Of note, nonimmunosuppressed, cell-augmented rats showed hardly any differences in cytokine expression in their grafts versus significant increases in their native livers. With immunosuppression, bone marrow infusion (versus blood transfusion) increased intragraft cytokine expression of IL-1α, IL-1β, IFN-γ, as well as TNF-α, and liver expression of IL-1β. Conclusions (1) Rejection and donor-specific cell augmentation independently caused differences in intragraft versus native liver cytokine expression after intestinal transplants. (2) Portal donor-specific blood transfusion (versus bone marrow infusion) lowered the incidence of rejection and diminished intragraft cytokine up-regulation. (3) In our study, TNF-α appeared to be the cytokine most strongly associated with rejection.