Gaud et al. inactivated (by Y to F mutations) the three CD3ζ chain ITAMs and generated mice that conditionally express the mutant CD3ζ chain (6F-CD3ζ) in mature post-selection T cells. T cells expressing TCRs containing 6F-CD3ζ (and ITAM-containing-CD3γ, δ and ε) exhibited reduced signaling and cytokine responses induced by high affinity ligands, enhanced TCR sensitivity to low affinity ligands – but not overt self-reactivity - and fewer distinct responses to ligands of varying affinity due to 6F-CD3ζ resistance to proximal negative feedback. 6F-CD3ζ-expressing T cells displayed enhanced cytolysis and control of solid tumors expressing low-affinity ligands.
Contributed by Paula Hochman
ABSTRACT: The T cell antigen receptor (TCR) contains ten immunoreceptor tyrosine-based activation motif (ITAM) signaling sequences distributed within six CD3 subunits; however, the reason for such structural complexity and multiplicity is unclear. Here we evaluated the effect of inactivating the three CD3ζ chain ITAMs on TCR signaling and T cell effector responses using a conditional 'switch' mouse model. Unexpectedly, we found that T cells expressing TCRs containing inactivated (non-signaling) CD3ζ ITAMs (6F-CD3ζ) exhibited reduced ability to discriminate between low- and high-affinity ligands, resulting in enhanced signaling and cytokine responses to low-affinity ligands because of a previously undetected inhibitory function of CD3ζ ITAMs. Also, 6F-CD3ζ TCRs were refractory to antagonism, as predicted by a new in silico adaptive kinetic proofreading model that revises the role of ITAM multiplicity in TCR signaling. Finally, T cells expressing 6F-CD3ζ displayed enhanced cytolytic activity against solid tumors expressing low-affinity ligands, identifying a new counterintuitive approach to TCR-mediated cancer immunotherapy.
Author Info: (1) Hematopoiesis and Lymphocyte Biology Section, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, Bethesda, MD, USA. (2) Immunodynamics Section, L
Author Info: (1) Hematopoiesis and Lymphocyte Biology Section, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, Bethesda, MD, USA. (2) Immunodynamics Section, Laboratory of Integrative Cancer Immunology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA. Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Kennedy Institute of Rheumatology, University of Oxford, Oxford, UK. (3) Dpartement de Biochimie et Mdecine Molculaire, Universit de Montral, Montral, Quebec, Canada. Department of Physics, McGill University, Montral QC, Canada. (4) Genitourinary Malignancies Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA. Department of Safety Assessment, Genentech, Inc., San Francisco, CA, USA. (5) Hematopoiesis and Lymphocyte Biology Section, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, Bethesda, MD, USA. (6) Hematopoiesis and Lymphocyte Biology Section, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, Bethesda, MD, USA. (7) Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA. (8) Viral Immunology & Intravital Imaging Section, National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA. (9) Hematopoiesis and Lymphocyte Biology Section, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, Bethesda, MD, USA. (10) National Institutes of Health Library, Office of Research Services, National Institutes of Health, Bethesda, MD, USA. (11) Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA. (12) Genitourinary Malignancies Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA. Duncan and Nancy MacMillan Cancer Immunology and Metabolism Center of Excellence, Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA. (13) Viral Immunology & Intravital Imaging Section, National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA. (14) Dpartement de Biochimie et Mdecine Molculaire, Universit de Montral, Montral, Quebec, Canada. Mila Qubec, Montral, Quebec, Canada. (15) Immunodynamics Section, Laboratory of Integrative Cancer Immunology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA. (16) Hematopoiesis and Lymphocyte Biology Section, Eunice Kennedy Shriver, National Institute of Child Health and Human Development, Bethesda, MD, USA. lovep@mail.nih.gov.
