**Abstract**

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 were replaced by those of another male patient.

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