Science Bite (3 minute oral presentation with PPT in live session and poster) - Students, ECRs and EMCRs only 15th Lorne Infection and Immunity 2025

Insights into the molecular recognition mechanism of a headless lipid by natural killer T cells (#308)

Praveena Thirunavukkarasu 1 , Tan-Yun Cheng 2 , Srinath Govindarajan 3 4 , Catarina F. Almeida 5 , Daniel G. Pellicci 5 , Wellington C. Arkins 2 , Ildiko Van Rhijn 2 , Koen Venken 3 4 , Dirk Elewaut 3 4 , Dale I. Godfrey 5 , D. Branch Moody 2 , Jamie Rossjohn 1 6
  1. Infection and Immunity program & Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
  2. Division of Rheumatology, Inflammation and Immunity, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
  3. Unit for Molecular Immunology and Inflammation,, VIB-Center for Inflammation Research,, Ghent, Belgium
  4. Department of Internal Medicine and Pediatrics,, Ghent University, , Ghent, Belgium
  5. Microbiology and Immunology, Peter Doherty institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia
  6. Institute of Infection and Immunity, Cardiff University, Heath Park, Cardiff, UK

In the absence of foreign lipids, Natural Killer T (NKT) cells display self-reactivity in conditions like autoimmunity, tumour immunity and graft-versus-host disease. Identifying the nature of self-lipids is a central aspect of understanding NKT cell self-reactivity. Using a high throughput lipidomics approach, we identified self-lipids bound to the antigen-presenting molecule CD1d from mammalian cells, which lacked the polar sugar head group that is normally involved in NKT T cell receptor (TCR) recognition. Our X-ray crystallography studies of NKT TCR binding to CD1d-presenting headless lipid antigen revealed the TCR adopted a parallel docking topology positioning itself atop the F’-pocket of CD1d. Surprisingly, the majority of intermolecular interactions in the complex were formed between CD1d and TCR itself with minimal interactions in contacting the lipid. The absence of the sugar headgroup abolished key interactions it normally displays with NKT TCR but, nevertheless, the overall conserved docking pattern was maintained. We also conducted a plate-bound assay using CD1d and headless self-lipids, which showed activation of the NKT cell hybridoma. Consistent with the activation results, CD1d tetramers treated with headless self-lipids stained the NKT cells. Surface Plasmon Resonance experiments showed that the NKT TCR bound the CD1d-headless lipid complex with micromolar affinities, which fall within the physiological range for activating ligands. Collectively, this study provides the first detailed insights into how a CD1d presenting a headless antigen is structurally recognised by the NKT TCR. Our data provides a proof of concept that small naturally occurring headless lipids could function as CD1d ligands in activating NKT cells.

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(* denotes equal first author)

Cheng TY*, Praveena T*, Govindarajan S*, Almeida CF*, Pellicci DG, Arkins WC, Van Rhijn I, Venken K, Elewaut D, Godfrey DI, Rossjohn J, Moody DB. Lipidomic scanning of self-lipids identifies headless antigens for natural killer T cells PNAS. 2024 Aug 20;121(34):e2321686121