Investigations of the immunoprotective role of the liver after allogeneic orthotopic combined liver-small-bowel transplantation in the rat

Combined small bowel and reduced auxiliary liver transplantation: Case report

AIM: To present a case of combined small bowel and reduced auxiliary liver transplantation.

METHODS: A 55-year-old patient with short bowel syndrome and TPN-related liver dysfunction received small bowel transplantation combined with a reduced auxiliary liver graft. A liver was added to restore the patient's liver function and to protect the intestinal allograft from rejection. His own liver was not removed.

RESULTS: Without donor pretreatment and by conventional immunosuppresive therapy following transplantation, the patient experienced had only one episode of mild intestinal rejection, which was easily reversed by treatment with Methylprednisolone. No liver rejection occurred. Unfortunately, the patient died of heart and lung failure 30 d after transplantation, despite successful graft replacement. Histopathologic examination of specimens after death demonstrated normal structure in both intestinal and liver grafts.

CONCLUSION: The auxiliary liver graft might play a role in preventing intestinal allograft rejection. However, the observation period in this case is short. Further study is needed to determine the risks, effect on the protecting the small-bowel from rejection, and feasibility of general application of this procedure.

Different kinetics of donor cell populations after isolated liver and combined liver/small bowel transplantation

Spontaneous tolerance induction after liver transplantation also supports additional transplants, e.g. a small bowel graft, from the same donor (tolerogenic effect). Chimerism serves as a possible explanation of this phenomenon. Isolated liver (LTx) and combined liver/small bowel transplantation (LSBTx) are compared. LSBTx and LTx were performed in the BN --> LEW rat strain combination without immunosuppression. Parenchymal damage during rejection was monitored by sequential standard histology. Donor/recipient populations were identified and further differentiated for immunohistochemical single and double staining. A small number of donor specific leukocytes can be detected on all days in host organs (microchimerism). A significantly larger donor leukocyte population survives long-term in the sinusoids of liver (graft chimerism). Sinusoidal donor leukocytes survive rejection and recover in number after tolerance induction. Rejection of liver allografts and infiltration by host leukocytes are more pronounced after LSBTx than after LTx. Accordingly, during rejection a steeper decline of sinusoidal donor leukocytes is observed after LSBTx and recovery after tolerance induction is not as marked. Microchimerism apparently plays no significant role in either transplantation model. The number of sinusoidal donor leukocytes, however, mirrors closely host immune responses.

Apoptosis of T lymphocytes in liver and/or small bowel allografts during tolerance induction

BACKGROUND

Apoptosis of parenchymal cells has been described during allograft rejection. Immunologically privileged tissue in the mouse has been found to prevent rejection by initiating apoptosis of infiltrating lymphocytes. The aim of this study was to investigate whether apoptosis may play a role in T-cell regulation during rejection and subsequent tolerance induction after liver transplantation (LTx) and combined liver/small bowel transplantation (LSBTx).

METHODS

LTx and LSBTx (Brown Norway-->Lewis) were performed without immunosuppression. Cell migration, activation, and apoptosis were investigated by means of sequential histology, immunohistochemistry, and the terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling assay. Donor (Brown Norway) and third-party (Dark Agouti) cardiac allografts were transplanted into LSBTx recipients to determine specific tolerance.

RESULTS

Transient acute cellular rejection occurred after LTx and LSBTx and was followed by specific tolerance. The kinetics of apoptosis were similar in liver allografts after LTx and LSBTx, but differed from the processes in small bowel allografts after LSBTx. Apoptosis of parenchymal cells in the grafted livers correlated directly with interleukin-2 receptor expression of the infiltrating T cells. During the late phase of rejection, a peak of apoptosis in the lymphocyte infiltrate was demonstrated, characterized as predominantly apoptotic CD8+ T lymphocytes.

CONCLUSIONS

These results demonstrate that specific tolerance is achieved in both LTx and LSBTx after a transient rejection crisis. Apoptosis is involved in graft rejection and tolerance induction. Activation of T lymphocytes correlates with parenchymal cell apoptosis in the allograft. T-cell inactivation seems to result in apoptosis of cytotoxic T cells and tolerance, which appears to be unique to the liver allograft.