Li et al. generated CD2 or CD48 (murine CD2 ligand) KO mice and tagged-CD2 knockin mice. CD2 KO or Ab blockade, or CD48 KO blunted in vitro TCR-stimulated T cell responses in the presence or absence of CD48+ APCs, while CD2-dependent T cell-mediated cytolysis in vitro partially required CD48+ APCs. GVHD was reduced by the absence of CD48, but more so CD2, on grafted T cells. FRET imaging and cell mixing showed CD2–CD48 cis interactions on individual T cells. T cell activation mediated via CD2 depended on CD2 cytoplasmic domain proline-rich motifs, which bound lck in vitro. Human CD2–CD58 (LFA-3, human CD2 ligand) cis interactions also promoted human TCR signaling.
Contributed by Paula Hochman
ABSTRACT: CD2 is largely described to promote T cell activation when engaged by its ligands, CD48 in mice and CD58 in humans, that are present on antigen-presenting cells (APCs). However, both CD48 and CD58 are also expressed on T cells. By generating new knockout mouse strains lacking CD2 or CD48 in the C57BL/6 background, we determined that whereas CD2 was necessary on T cells for T cell activation, its ligand CD48 was not required on APCs. Rather, CD48 was also needed on T cells. One exception was during cytotoxicity, which required CD48 on T cells and APCs. Fluorescence resonance energy transfer (FRET) studies in nonimmune cells provided evidence that cis interactions between CD2 and CD48 existed within individual cells. CD2-CD48 interactions on T cells enabled more robust T cell receptor (TCR) signals, including protein tyrosine phosphorylation. Using T cells from a CD2 knock-in mouse in which a tag was inserted at the carboxyl terminus of CD2, mass spectrometry analyses revealed that the role of CD2 in T cell activation correlated with its ability to interact with components of the TCR complex and the protein tyrosine kinase Lck. CD2-CD58 provided a similar function in human T cells. Thus, our data imply that T cell-intrinsic cis interactions of CD2 with its ligands are required for TCR signaling and T cell activation. Interactions with ligands on APCs contribute during cytotoxicity.
Author Info: (1) Laboratory of Molecular Oncology, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada. Molecular Biology Program, University of Montréal, Mont
Author Info: (1) Laboratory of Molecular Oncology, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada. Molecular Biology Program, University of Montréal, Montréal, Québec H3T 1J4, Canada. (2) Laboratory of Molecular Oncology, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada. (3) Laboratory of Molecular Oncology, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada. (4) Laboratory of Molecular Oncology, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada. (5) Laboratory of Molecular Oncology, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada. Department of Medicine, McGill University, Montréal, Québec H3G 1Y6, Canada. (6) Laboratory of Molecular Oncology, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada. (7) Laboratory of Molecular Oncology, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada. (8) Laboratory of Molecular Oncology, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada. Department of Medicine, McGill University, Montréal, Québec H3G 1Y6, Canada. (9) Centre d'Immunologie de Marseille-Luminy, Aix Marseille Université, INSERM, CNRS, 13288 Marseille, France. (10) Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS UPS, Toulouse, France. (11) Centre d'Immunologie de Marseille-Luminy, Aix Marseille Université, INSERM, CNRS, 13288 Marseille, France. Centre d'Immunophnomique, Aix Marseille Université, INSERM, CNRS, 13288 Marseille, France. (12) Centre d'Immunologie de Marseille-Luminy, Aix Marseille Université, INSERM, CNRS, 13288 Marseille, France. (13) Laboratory of Molecular Oncology, Institut de recherches cliniques de Montréal (IRCM), Montréal, Québec H2W 1R7, Canada. Molecular Biology Program, University of Montréal, Montréal, Québec H3T 1J4, Canada. Department of Medicine, McGill University, Montréal, Québec H3G 1Y6, Canada.
