Immunological Aspects of Organ Transplantation

**89**

**Chapter 5**

**Abstract**

apoptosis, tolerance

**1. Introduction**

*Tatsuaki Tsuruyama*

Pathology of Intestinal

and a Case of Tolerance

were replaced by those of another male patient.

**1.1 Current status of small bowel transplantation**

management after transplantation [6, 7].

Transplantation: Rejection

Small bowel transplants are less common than other organ transplants. Histological criteria for rejection of the transplanted small intestine were proposed at the 8th International Symposium on Small Intestinal Transplantation 2003-2004. The Banff Conference on Transplant Disease Pathology, an international conference on the rejection of small bowel transplants, was held in 2019, and unifying diagnostic criteria were discussed (https://banfffoundation.org/pittsburgh-2019/). These histological criteria are expected to be standardized in the near future. This review outlines new findings such as apoptosis and apoptotic-body phagocytic findings in the lamina propria and behavior of natural killer T (NKT) cells, in addition to previously known crypt Fas-related apoptosis in acute cellular rejection. Furthermore, we review the case of a recipient who has shown no rejection for 5 years after transplantation. In the transplanted small intestine of this patient, the lymphocytes

**Keywords:** intestinal transplantation, histology, rejection, natural killer T cells,

Small bowel transplantation (SBT) is one of the standard treatments for patients

Acute cellular rejection (ACR) is a major cause of impaired colonization by the transplanted small intestine, and it frequently accompanies chronic and irreversible changes such as ulcers and lamina propria fibrosis. ACR has remained a risk factor that impedes functional recovery of the intestinal graft [1, 8, 9]. On the other hand, pathologists frequently encounter various pathologies of the intestinal allograft [10–12]. For example, mechanical failure of the graft due to operation during

who are unable to consume a regular diet and have complications from the irreversible requirement of parenteral nutrition [1]. Hirschsprung's disease [2, 3] and Crohn's disease [4] patients are two examples. Recent effective immunosuppressive drugs, well-controlled postoperative care, and advances in diagnostic techniques have significantly improved the outcome of SBT [5]. Immunosuppressants such as mycophenolate mofetil, tacrolimus, and steroids, are routinely used for long-term
