Immune Memory After Intestinal Transplantation – what can we learn from T cell immunophenotypes over time?

Abstract

Introduction: Examination of peripheral blood mononuclear cells (PBMCs) via immunophenotyping has been shown to be a useful, non-invasive method of diagnosing acute cellular rejection (ACR) following intestinal transplantation (ITx).[1] Aims: To characterize (1) differences in the peripheral blood T cell immunophenotype during episodes of ACR and viral enteritis and (2) changes in naïve and central/effector memory T cells over time. Methods: An IRB-approved, longitudinal study of ITx recipients was performed. Blood was collected during serial routine visits at least 6 months apart and episodes of graft dysfunction (high fecal outputs, nausea/vomiting, and/or gastrointestinal bleeding). Samples from routine visits were classified as early post-ITx (<5 yrs) and late post-ITx (>5 yrs). PBMC immunophenotyping was performed with multi-color monoclonal antibody panels. Cell fluorescence was acquired on an LSR Fortessa. Analysis was performed with Flowjo V10. Statistical analyses included t-tests using Stata. Results: 11 pediatric ITx recipients who received 14 grafts were included. 57% were liver-intestinal grafts. 28 samples were analyzed (range of 1–5 samples per patient): 20 were collected on routine visits and 8 during episodes of graft dysfunction. There were no significant differences in markers of exhaustion (PD1+, KLRG1+, CD57+), Th17 effector cells, or T regulatory cells in normal (n=11) vs graft dysfunction (n=8). There were multiple statistically significant differences in T cell subsets in the early (n=7) vs late (n=13) groups (Table 1). Naïve T cells were higher in the early post-ITx group and T central memory cells were higher in the late post-ITx group. Conclusion: Over time, there is a shift in the T cell immunophenotype from naïve to central memory cells. Additional studies are needed with larger cohorts to identify T cell differences associated with episodes of graft dysfunction. Further elucidating T cell immunophenotypes over time will lead to a better understanding of immune memory and its clinical implications in ITx.FigureReference: 1. Ashokkumar C et al. Allospecific CD154+ T cells identify rejection-prone recipients after pediatric small-bowel transplantation. Surgery. 2009; 146:166–73.