T Cells at the Site of Autoimmune Inflammation Show Increased Potential for Trogocytosis

Bettina Haastert,Stephen M Anderton,Richard J Mellanby,Richard A O'Connor

doi:10.1371/journal.pone.0081404

Bettina Haastert, Stephen M Anderton + Show 2 more

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https://doi.org/10.1371/journal.pone.0081404

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Abstract

CD4+ T cells acquire membrane fragments from antigen-presenting-cells via a process termed trogocytosis. Identifying which CD4+ T cells undergo trogocytosis in co-culture with Ag-loaded APC can enrich for antigen-reactive T cells without knowledge of their fine specificity or cytokine-production profiles. We sought to assess the suitability of this method to identify disease relevant effector and regulatory T cells during autoimmune inflammation. Trogocytosis efficiently identified MBP-reactive T cells in vitro and ex-vivo following immunization. However, Foxp3+ regulatory T cells constitutively displayed a higher rate of trogocytosis than their Foxp3- counterparts which limits the potential of trogocytosis to identify antigen-reactive Treg cells. During inflammation a locally elevated rate of trogocytosis (seen in both effector and regulatory T cells isolated from the inflamed CNS) precludes the use of trogocytosis as a measure of antigenic reactivity among cells taken from inflammatory sites. Our results indicate trogocytosis detection can enrich for Ag-reactive conventional T cells in the periphery but is limited in its ability to identify Ag-reactive Treg or T effector cells at sites of inflammation. Increased trogocytosis potential at inflammatory sites also draws into the question the biological significance of this phenomenon during inflammation, in Treg mediated suppression and for the maintenance of tolerance in health and disease.

Highlights

The process of rapid, cell-to-cell, contact-dependent transfer of plasma membrane fragments between immune cells, termed trogocytosis from the Greek ‘‘to gnaw’’, has recently attracted considerable attention
Having shown enhanced trogocytosis in CD4+ Tg4 T cells upon contact with their cognate antigen, we explored the possibility of using trogocytosis as a method to detect antigen-reactive CD4+ T cells in a mixed population
We assessed the potential of trogocytosis to detect antigenresponsive FoxP3+ and FoxP32 CD4+ T cells derived from a site of autoimmune inflammation – the inflamed CNS during EAE

Summary

Introduction

The process of rapid, cell-to-cell, contact-dependent transfer of plasma membrane fragments between immune cells, termed trogocytosis from the Greek ‘‘to gnaw’’, has recently attracted considerable attention. To detect cells which have performed trogocytosis, antigen-pulsed APCs are labelled with biotin or lipophilic dyes and co-cultured with T cells, T cells which have acquired membrane fragments from the APC can thereafter be detected by their acquisition of the label [1,6] This technique has been used effectively to quantify virus specific [6,7], tumor specific [2,8]and auto-reactive T cells [5]. The advantages of this method over the use of ELISPOT and other cytokine-based approaches or MHC-tetramers are its independence of cytokine production and its usefulness in situations where the fine specificity of responding T cells is unknown.

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