Inhibition of donor-derived T cells trafficking into target organs by FTY720 during acute graft-versus-host disease in small bowel transplantation

Abstract

In small bowel transplantation (SBTx), graft-versus-host disease (GVHD) is mediated by donor-derived T cells recognizing host major histocompatibility complex (MHC) alloantigens, and represents an important immunological event influencing life in experimental and clinical situations. We evaluated the possibility that a new sphingosine 1-phosphate receptor agonist, FTY720, could diminish GVHD in a rat SBTx model through traffic alteration of donor-derived T cells in target organs. Heterotopic SBTx was performed using a parent (WF)-into-F(1) (WF x ACI) rat combination. Recipient survival, body weight, histopathology, donor-derived T cell subpopulation and cytokine production were compared with untreated controls. FTY720 inhibited lethality and histopathological changes in target organs when administered at 0.5 mg/kg, possibly due to sequestration of donor-derived T cells in the intestinal graft. FTY720 caused a significant reduction in donor T cell numbers in target organs by promoting these cells to home into donor, but not recipient, secondary lymphoid tissues. FTY720 significantly decreased production of interferon (IFN)-gamma in target organs. These findings indicate that FTY720 effectively reduced recirculation of activated donor-derived T cells and recruitment to target organs in GVHD, and was also associated with down-regulated IFN-gamma production. These properties may offer the potential to treat ongoing GVHD in SBTx.

Fig. 1

Postoperative weight change following small bowel transplantation in rats. Semiallogeneic parent-to-F₁ model of GVHD by FTY720 (0·5 mg/kg)-treated recipients show progressive weight gain; another group (0·1 mg/kg) gained weight until the onset of lethal GVHD, but resulted in weight loss and death. Data are expressed as mean ± SD. Syngeneic (open circle, n = 6), no treatment (open diamond, n = 8), FTY 0·1 mg/kg (close square, n = 6), FTY 0·5 mg/kg (close triangle, n = 8).

Fig. 2

FTY720 treatment of graft-versus-host disease (GVHD) rats results in inhibited intestinal, hepatic and skin histopathology. On day 14, small bowel, hepatic and skin samples from small bowel transplantation recipients were obtained and analysed microscopically. Untreated GVHD rats showed severe intestinal histopathology, including mucosal erosion, villous blunting and cellular infiltration in the lamina propria (arrow) and prominent lymphocyte infiltration in the periportal area of the liver (arrow). Skin histopathology showed prominent cellular infiltration and atrophy of skin appendages (arrow). FTY720 treatment inhibited histopathological changes in the small bowel, liver and skin (original magnification; × 100, small bowel and liver; × 40, skin).

Fig. 3

Effect of FTY720 treatment on the lymphocyte numbers of donor derived T cells. Lymphocytes of peripheral blood (a), target organs of the host (b) and graft (c) were prepared from naive Wistar–Furth rats, acute graft-versus-host disease and FTY720-treated rats as described in Materials and methods. Donor-derived T cells were determined by multiplying the total number of cells by the fraction of RT1A^ab-negative and T cell receptor (TCR)αβ-, TCRγδ- CD4- and CD8-positive cells. Five rats were analysed from each group. Data are expressed as mean ± s.d. *P < 0·05; **P < 0·01. αβT, TCR αβ T cell; γδT, TCR γδ T cell.

Fig. 4

Cytokine profile by target tissue lymphocytes after daily administration of FTY720 0·5 mg/kg for 14 days. In the treatment group (a) interferon-γ production in target tissues was diminished significantly. However, no significant differences were noted in production of interleukin-4 (b) by the liver, Peyer’s patches, mesenteric lymph node and lamina propria lymphocytes. Data are expressed as mean ± s.d. Four rats were analysed from each group. *P < 0·05; **P < 0·01.