Characterization of T cell immunophenotypes in intestinal transplantation: A pilot study

Highlights

• The CD4 T cell immunophenotype is enriched with more central memory cells in blood samples collected late vs early after ITx.

• There are increased T cell activation markers in rejection compared to infectious enteritis and normal samples.

• Immunophenotyping is valuable in elucidating immune mechanisms of allograft dysfunction and identifying biomarkers in ITx.

Abstract

Immunophenotyping of peripheral blood mononuclear cells has been shown to be a useful, non-invasive method of predicting acute cellular rejection (ACR) following intestinal transplantation (ITx). Our objectives were to characterize differences in the T cell immunophenotype of ITx recipients in peripheral blood samples (1) collected late versus early after ITx and (1) associated with episodes of ACR and infectious enteritis. An IRB-approved, cross-sectional study of ITx recipients was performed. Peripheral blood samples were collected during normal visits and episodes of allograft dysfunction. A total of 38 patients were included in the analysis: 31 ITx recipients (87% liver-inclusive allografts) and 7 intestinal failure control patients. Of the ITx patients, 26 patients were pediatric patients (<21 years). A total of 70 samples were analyzed from ITx recipients, including 51 during normal visits and 19 during episodes of allograft dysfunction (median of 2 samples per patient; range of 1–6 samples per patient). In the late (n = 32) versus early post-ITx (n = 19) normal samples, there was a significantly higher percentage of central memory CD4 T cells (p = .001). In the ACR (n = 5) versus infectious enteritis (n = 14) samples, there was a higher percentage of CD8 T cells expressing HLA-DR (p = .002), CD57 (p < .001), and KLRG1 (p < .001) and a higher percentage of CD4 T cells expressing CD57 (p = .03). Additional studies are needed with larger cohorts to validate these changes in the T cell immunophenotype. Further elucidating T cell immunophenotypes in ITx will lead to a better understanding of immune mechanisms of allograft dysfunction, identification of potential biomarkers in ITx, and optimized selection of immunosuppressive therapies.

Introduction

Intestinal transplantation (ITx) is a lifesaving procedure for patients with irreversible intestinal failure who have complications of parenteral nutrition, an inability to adapt to the quality-of-life limitations posed by intestinal failure, and/or a high risk of death if the native intestine is not removed [1]. Modest improvements have been made in early graft survival rates over the past decade, but rates of allograft loss beyond one year have not improved [2]. A significant barrier to successful ITx is acute cellular rejection (ACR). ACR continues to affect almost 40% of ITx recipients in the first year after transplantation [3] with potentially devastating consequences. ACR also remains an important cause of late allograft loss [4].

In the setting of intestinal allograft dysfunction, a major challenge is the differentiation of ACR from infectious enteritis. Infectious enteritis is a common cause of allograft dysfunction, occurring in up to three quarters of pediatric ITx recipients [5]. Although the gold standard for diagnosis of ACR is endoscopy with biopsy to identify key histopathologic findings [6], there are inherent disadvantages to endoscopy. Histopathology obtained from endoscopy is subject to sampling and interpretation error [7], with newer grading scores being proposed [8]. In addition, endoscopy is associated with higher risks of complications in pediatric ITx recipients [9] as well as a significant burden of cost [10]. Thus, there remains a clear need for a non-invasive means to discriminate between ACR and infectious enteritis.

Although multiple prior attempts to develop non-invasive biomarkers of immune monitoring in ITx have been suboptimal [[11], [12], [13], [14]], immunophenotyping of T cells has been shown to be a useful, non-invasive method of predicting ACR in pediatric ITx [15,16]. Peripheral blood mononuclear cells (PBMCs), including T cells, offer a unique window through which the recipient's immune response to transplanted tissue can be monitored non-invasively. These cells are present in the peripheral blood after allo-endothelial-cell contact in the allograft due to recirculation. Immunophenotyping of specific T cell subsets have also been associated with ACR in pediatric liver transplantation [17,18] and adult renal transplantation [19].

We performed a cross-sectional, single center, pilot study to monitor peripheral blood T cell immunophenotypes at various time intervals following ITx and across clinical states (ACR, infectious enteritis, and normal baseline stability).