FAS-controlled T cells undergo normal thymic selection and can differentiate from a broad range of early-differentiated peripheral CD4+ or CD8+ T cells
KOENIG C. 1,2, KURY P. 1, MACCARI M. 1,3, BERGER S. 1,2, FRONKOVA E. 4, SKOTNICOVA A. 4, ULLRICH E. 5, KROLL J. 6, LORENZ M. 7, SCHWARZ K. 7,8, SPECKMANN C. 1,3, STUCHLY J. 4, KALINA T. 4, EHL S. 1,3, RENSING-EHL A. 1
1 Institute for Immunodeficiency, Center for Chronic Immunodeficiency (CCI), Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, Freiburg, Germany; 2 University of Freiburg, Faculty of Biology, Schaenzlestrasse 1, D–79104, Germany, Freiburg, Germany; 3 Division of Pediatric Hematology and Oncology, Department of Pediatrics and Adolescent Medicine, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Mathildenstr. 1, 79106, Germany, Freiburg, Germany; 4 CLIP-Childhood Leukemia Investigation Prague, Department of Pediatric Hematology and Oncology, 2nd Medical School, Charles University and University Hospital Motol, Czech Republic, Prague, Czechia; 5 Children's Hospital, Experimental Immunology, Goethe-University Frankfurt, 60590, Germany, Frankfurt Am Main, Germany; 6 Department of Cardiovascular Surgery, University Heart Center Freiburg-Bad Krozingen, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, Freiburg, Germany; 7 Institute for Transfusion Medicine, University of Ulm, Germany, Ulm, Germany; 8 Institute for Clinical Transfusion Medicine and Immunogenetics Ulm, German Red Cross Blood Service Baden-Wuerttemberg–Hessen, Germany, Ulm, Germany
Background & Objectives
Differentiation and lifespan of T cells have to be precisely balanced to maintain homeostasis and self-tolerance. We recently described a FAS-controlled (FC) subset of TCRαβ+ T cells that is characterized by a unique molecular signature unambiguously separating it from other known conventional T cell subsets. FC T cells represent a small proportion of CD4+, CD8+ and double negative T cells (DNT) in healthy individuals but massively expand in FAS-deficient patients with autoimmune lymphoproliferative syndrome (ALPS). Origin, differentiation and function of this highly proliferative T cell subset are currently not understood. Our goal was to delineate ontogeny and TCR repertoire characteristics of FC T cells. We hypothesized that FC T cell fate induction and differentiation do not occur in the thymus but in normally selected mature peripheral T cells.
We combined mass cytometry analyses and bioinformatics tools to model FC T cell ontogeny from thymocytes to peripheral T cells. In addition, we performed TCR Vβ deep sequencing and TREC quantification of sorted T cell subsets to assess imprints of thymic selection, TCR repertoire and possible differentiation trajectories.
Developmental pathways modelled for FC T cells followed the same intrathymic trajectories as observed for conventional T cell subsets. FC T cells branched off from resting naïve or early memory T cells. TREC level analyses further supported lineage segregation from conventional T cells at stages prior to terminal differentiation. Importantly, FC T cells showed signs of normal thymic selection and high TCR Vβ repertoire diversity with substantial sequence overlap to conventional CD4+ and CD8+ T cells.
Our data suggest normal thymic development and peripheral induction of FC T cell differentiation primarily at a naïve stage including a large range of specificities. Our findings are currently being validated using scRNASeq analyses and murine model systems.