Quantification of Intraepithelial Lymphocytes in Normal Pediatric Small Intestinal Allograft and Native Ilea

Immune cell profiling in intestinal transplantation

Since the first published case study of human intestinal transplantation in 1967, there have been significant studies of intestinal transplant immunology in both animal models and humans. An improved understanding of the profiles of different immune cell subsets is critical for understanding their contributions to graft outcomes. While different studies have focused on the contribution of one or a few subsets to intestinal transplant, no study has integrated these data for a comprehensive overview of immune dynamics after intestinal transplant. Here, we provide a systematic review of the literature on different immune subsets and discuss their roles in intestinal transplant outcomes on multiple levels, focusing on chimerism and graft immune reconstitution, clonal alloreactivity, and cell phenotype. In Sections 1, 2 and 3, we lay out a shared framework for understanding intestinal transplant, focusing on the mechanisms of rejection or tolerance in the context of mucosal immunology and illustrate the unique role of the bidirectional graft-versus-host (GvH) and host-versus-graft (HvG) alloresponse. In Sections 4, 5 and 6, we further expand upon these concepts as we discuss the contribution of different cell subsets to intestinal transplant. An improved understanding of intestinal transplantation immunology will bring us closer to maximizing the potential of this important treatment.

Innate Lymphoid Cells Groups 1 and 3 in the Epithelial Compartment of Functional Human Intestinal Allografts

We examined intraepithelial lymphocytes (IELs) in 213 ileal biopsies from 16 bowel grafts and compared them with 32 biopsies from native intestines. During the first year posttransplantation, grafts exhibited low levels of IELs (percentage of CD103(+) cells) principally due to reduced CD3(+) CD8(+) cells, while CD103(+) CD3(-) cell numbers became significantly higher. Changes in IEL subsets did not correlate with histology results, isolated intestine, or multivisceral transplants, but CD3(-) IELs were significantly higher in patients receiving corticosteroids. Compared with controls, more CD3(-) IELs of the grafts expressed CD56, NKp44, interleukin (IL)-23 receptor, retinoid-related orphan receptor gamma t (RORγt), and CCR6. No difference was observed in granzyme B, and CD3(-) CD127(+) cells were more abundant in native intestines. Ex vivo, and after in vitro activation, CD3(-) IELs in grafts produced significantly more interferon (IFN)-γ and IL-22, and a double IFNγ(+) IL-22(+) population was observed. Epithelial cell-depleted grafts IELs were cytotoxic, whereas this was not observed in controls. In conclusion, different from native intestines, a CD3(-) IEL subset predominates in grafts, showing features of natural killer cells and intraepithelial ILC1 (CD56(+) , NKp44(+) , CCR6(+) , CD127(-) , cytotoxicity, and IFNγ secretion), ILC3 (CD56(+) , NKp44(+) , IL-23R(+) , CCR6(+) , RORγt(+) , and IL-22 secretion), and intermediate ILC1-ILC3 phenotypes (IFNγ(+) IL-22(+) ). Viability of intestinal grafts may depend on the balance among proinflammatory and homeostatic roles of ILC subsets.

Collagenous colitis in children and adolescents: study of 7 cases and literature review

The aim of this study is to examine the clinical and pathologic characteristics of collagenous colitis (CC) in children and adolescents. Seven patients (five females and two males, median age: 13 years, ranging from 4 to 16) were included. Four (of 7, 57%) patients presented with non-bloody watery diarrhea, one with alternating constipation and diarrhea with rectal prolapse, one with constipation, and one with normal bowel movement. Abdominal pain and weight loss were manifested in 80 and 40% patients, respectively. Two patients had celiac disease in remission. None of the patients took non-steroidal antiinflammatory agents. All patients had normal colonoscopy, but had typical histologic features of CC in colon biopsies. Four patients had clinical follow-up (24-75 months duration, median 54 months): three patients had no gastrointestinal symptoms upon follow-up, but one patient had continued symptoms of alternating diarrhea and constipation. Two patients had follow-up biopsies: one showed persistence of CC, and one had complete histologic resolution. We conclude that while CC is rare in children and adolescents, the clinical presentation is similar to adults, with a female preponderance, presentation with diarrhea and abdominal pain, and an association with celiac disease and other autoimmune disorders. However, compared with adults, children and adolescents are more likely to have weight loss and an atypical presentation including alternating constipation and diarrhea, constipation alone or normal bowel movements. Treatment is less standardized in children and adolescents with CC.

Physiology of the small intestine after resection and transplant

PURPOSE OF REVIEW

Recent studies have evaluated intestinal physiology following bowel resection; understanding changes in small bowel physiology after intestinal transplantation has received less attention. In this review, we will examine recent studies focused on changes in intestinal physiology following resection and intestinal transplantation.

RECENT FINDINGS

Absorption, immunity, and motility are fundamental components of small bowel physiology. Absorption after resection or transplantation is mediated by adaptation and enterocyte function. After resection, adaptation results in increased villus height and crypt depth. Hepatocyte growth factor and epidermal growth factors cause enterocyte hypertrophy and hyperplasia, allowing greater peptide uptake. Little is known about intestinal adaptation after transplant, but enteral autonomy is attainable. Immunity in small bowel after transplantation relies on a balance of innate and adaptive immune responses in the presence of the luminal microbiota. Intraepithelial lymphocytes are decreased following small bowel resection. After small bowel transplant, the number and the ratio of intraepithelial lymphocytes to enterocytes, as well as changes in the microbiota, can be used to identify rejection. After intestinal transplant, immune-mediated dysmotility is common. Perioperative infliximab in addition to tacrolimus may decrease the inflammation that contributes to dysmotility.

SUMMARY

As intestinal transplantation becomes more successful, understanding how absorption, immunity, and motility changes will allow for optimization of bowel function.