Live-cell imaging reveals the relative contributions of antigen-presenting cell subsets to thymic central tolerance

J N Lancaster,Y Li,J Srinivasan,Z Hu,L I R Ehrlich,H M Thyagarajan

doi:10.1038/s41467-019-09727-4

J N Lancaster, Y Li + Show 4 more

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https://doi.org/10.1038/s41467-019-09727-4

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Journal: Nature Communications	Publication Date: May 17, 2019
Citations: 42	License type: open-access

Affiliation: The University of Texas at Austin

Abstract

Both medullary thymic epithelial cells (mTEC) and dendritic cells (DC) present tissue-restricted antigens (TRA) to thymocytes to induce central tolerance, but the relative contributions of these antigen-presenting cell (APC) subsets remain unresolved. Here we developed a two-photon microscopy approach to observe thymocytes interacting with intact APCs presenting TRAs. We find that mTECs and DCs cooperate extensively to induce tolerance, with their relative contributions regulated by the cellular form of the TRA and the class of major histocompatibility complex (MHC) on which antigen is presented. Even when TRA expression is restricted to mTECs, DCs still present self-antigens at least as frequently as mTECs. Notably, the DC subset cDC2 efficiently acquires secreted mTEC-derived TRAs for cross-presentation on MHC-I. By directly imaging interactions between thymocytes and APCs, while monitoring intracellular signaling, this study reveals that distinct DC subsets and AIRE+ mTECs contribute substantially to presentation of diverse self-antigens for establishing central tolerance.

Highlights

Both medullary thymic epithelial cells and dendritic cells (DC) present tissuerestricted antigens (TRA) to thymocytes to induce central tolerance, but the relative contributions of these antigen-presenting cell (APC) subsets remain unresolved
A distinct advantage of this approach is its ability to reveal the redundant capacity of both medullary thymic epithelial cells (mTEC) and DCs to present a given TRA to induce tolerance of a monoclonal thymocyte population. We find that both AIRE+ mTECs and DCs contribute substantially to presentation of a single TRA to CD4SP and CD8SP thymocytes, the relative contribution of each APC varies according to the subcellular localization of the TRA and presentation on major histocompatibility complex (MHC)-I versus MHC-II
We developed a 2PM approach to visualize the migration and activation of SP thymocytes as they encounter negatively selecting ligands presented by AIRE+ mTECs or DCs in the thymic medulla (Fig. 1a)

Summary

Introduction

Both medullary thymic epithelial cells (mTEC) and dendritic cells (DC) present tissuerestricted antigens (TRA) to thymocytes to induce central tolerance, but the relative contributions of these antigen-presenting cell (APC) subsets remain unresolved. Studies addressing the relative contributions of mTECs and DCs to central tolerance have used genetic models that either ablate mTECs or DCs, or inhibit their ability to present selfantigens[13,14,15,16,17,23, 27,28,29,30,31] These studies address the intrinsic capacity of mTECs or DCs to mediate selection in the absence of the other cell type, and can identify TCRs via repertoire sequencing that require either APC subset for selection, they cannot address the roles of mTECs and DCs when both are intact. Genetically altering one stromal cell subset can impair maturation of others, making it difficult to deduce the physiologic contribution of different APCs to central tolerance

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