Butyrophilin-2A1 Directly Binds Germline-Encoded Regions of the Vγ9Vδ2 TCR and Is Essential for Phosphoantigen Sensing

Mohindar M Karunakaran1, Carrie R Willcox2, Mahboob Salim2, Daniel Paletta1, Alina S Fichtner1, Angela Noll3, Lisa Starick1, Anna Nöhren1, Charlotte R Begley2, Katie A Berwick2, Raphaël A G Chaleil4, Vincent Pitard5, Julie Déchanet-Merville5, Paul A Bates4, Brigitte Kimmel6, Timothy J Knowles7, Volker Kunzmann6, Lutz Walter3, Mark Jeeves8, Fiyaz Mohammed2, Benjamin E Willcox9, Thomas Herrmann10

  1. Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany.
  2. Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK; Cancer Immunology and Immunotherapy Centre, University of Birmingham, Birmingham, UK.
  3. Primate Genetics Laboratory, German Primate Center, Leibniz Institute for Primate Research, Göttingen, Germany.
  4. Biomolecular Modelling Laboratory, The Francis Crick Institute, London, UK.
  5. ImmunoConcEpT Laboratory, Equipe labellisée, LIGUE 2017, UMR 5164, Bordeaux University, CNRS, 33076 Bordeaux, France; Flow Cytometry Facility, TransBioMed Core, Bordeaux University, CNRS UMS 3427, INSERM US05, 33076 Bordeaux, France.
  6. Medical Clinic and Policlinic II, University of Würzburg, Würzburg, Germany.
  7. School of Biosciences, University of Birmingham, Birmingham, UK.
  8. Henry Wellcome Building for NMR, Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, UK.
  9. Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, UK; Cancer Immunology and Immunotherapy Centre, University of Birmingham, Birmingham, UK. Electronic address: b.willcox@bham.ac.uk.
  10. Institute for Virology and Immunobiology, University of Würzburg, Würzburg, Germany. Electronic address: herrmann-t@vim.uni-wuerzburg.de.

Abstract

Vγ9Vδ2 T cells respond in a TCR-dependent fashion to both microbial and host-derived pyrophosphate compounds (phosphoantigens, or P-Ag). Butyrophilin-3A1 (BTN3A1), a protein structurally related to the B7 family of costimulatory molecules, is necessary but insufficient for this process. We performed radiation hybrid screens to uncover direct TCR ligands and cofactors that potentiate BTN3A1's P-Ag sensing function. These experiments identified butyrophilin-2A1 (BTN2A1) as essential to Vγ9Vδ2 T cell recognition. BTN2A1 synergised with BTN3A1 in sensitizing P-Ag-exposed cells for Vγ9Vδ2 TCR-mediated responses. Surface plasmon resonance experiments established Vγ9Vδ2 TCRs used germline-encoded Vγ9 regions to directly bind the BTN2A1 CFG-IgV domain surface. Notably, somatically recombined CDR3 loops implicated in P-Ag recognition were uninvolved. Immunoprecipitations demonstrated close cell-surface BTN2A1-BTN3A1 association independent of P-Ag stimulation. Thus, BTN2A1 is a BTN3A1-linked co-factor critical to Vγ9Vδ2 TCR recognition. Furthermore, these results suggest a composite-ligand model of P-Ag sensing wherein the Vγ9Vδ2 TCR directly interacts with both BTN2A1 and an additional ligand recognized in a CDR3-dependent manner.

Presented by Mohindar M. Karunakaran and Carrie R. Willcox

Immunology & MicrobiologyNicholas Liao2020- 03 (Mar)