A Functional cdTCR/CD3 Complex Distinct from cdT Cells Is Expressed by Human Eosinophils Fanny Legrand1,2,3., Virginie Driss1,2,3., Gae¨ tane Woerly1,2,3, Sylvie Loiseau1,2,3, Emmanuel Hermann1,2,3, Jean-Jacques Fournie´ 4, Laurent He´ liot2,3,5, Virginie Mattot2,3,5, Fabrice Soncin2,3,5, Marie-Lise Gougeon 6 , David Dombrowicz1,2,3", Monique Capron1,2,3"* 1 Inserm U547, Lille, France, 2 Universite´ Lille - Nord de France, Lille, France, 3 Institut Pasteur de Lille, Lille, France, 4 Inserm, U 563, Toulouse, France, 5 CNRS UMR8161, Institut de Biologie de Lille, Lille, France, 6 Institut Pasteur, Paris, France Abstract Background: Eosinophils are effector cells during parasitic infections and allergic responses. However, their contribution to innate immunity has been only recently unravelled. Methodology/Principal Findings: Here we show that human eosinophils express CD3 and cd T Cell Receptor (TCR) but not ab TCR. Surface expression of cdTCR/CD3 is heterogeneous between eosinophil donors and inducible by mycobacterial ligands. Surface immunoprecipitation revealed expression of the full cdTCR/CD3 complex. Real-time PCR amplification for CD3, c and d TCR constant regions transcripts showed a significantly lower expression in eosinophils than in cdT cells. Limited TCR rearrangements occur in eosinophils as shown by spectratyping analysis of CDR3 length profiles and in situ hybridization. Release by eosinophils of Reactive Oxygen Species, granule proteins, Eosinophil Peroxidase and Eosinophil- Derived Neurotoxin and cytokines (IFN-c and TNF-a) was observed following activation by cdTCR-specific agonists or by mycobacteria. These effects were inhibited by anti-cdTCR blocking antibodies and antagonists. Moreover, cdTCR/CD3 was involved in eosinophil cytotoxicity against tumor cells. Conclusions/Significance: Our results provide evidence that human eosinophils express a functional cdTCR/CD3 with similar, but not identical, characteristics to cdTCR from cdT cells. We propose that this receptor contributes to eosinophil innate responses against mycobacteria and tumors and may represent an additional link between lymphoid and myeloid lineages. Citation: Legrand F, Driss V, Woerly G, Loiseau S, Hermann E, et al. (2009) A Functional cdTCR/CD3 Complex Distinct from cdT Cells Is Expressed by Human Eosinophils. PLoS ONE 4(6): e5926. doi:10.1371/journal.pone.0005926 Editor: Derya Unutmaz, New York University School of Medicine, United States of America Received April 1, 2009; Accepted May 13, 2009; Published June 17, 2009 Copyright: 2009 Legrand et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Work was funded by Inserm (French National Institutes for Health and Medical Reserach), Pasteur Institute Lille (a not for profit Research Institute), University Lille - Nord de France and ANR (French National Research Agency). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: monique.capron@pasteur-lille.fr . These authors contribued equally to this work. " These authors also contribued equally to this work. Introduction Eosinophils are polymorphonuclear granulocytes mainly found in increased numbers during helminth parasitic infections and allergic reactions [1,2]. They are classically considered as mediator-releasing cells during effector phase of adaptive immu- nity, under the influence of T cell dependent cytokines or chemokines and antibodies [2], whereas eosinophil-derived chemokines have been recently shown to locally attract Th2 lymphocytes at lung inflammatory sites [3,4]. Nevertheless, their precise function as beneficial or deleterious to the host still remains ambiguous, since highly toxic proteins present in eosinophil granules exert potent cytotoxic effects against non self targets such as parasites [5,6] but also against stressed or necrotic host cells [7] and in asthma [8]. Eosinophils are foremost present in mucosal tissues in contact with the environment such as in gastro-intestinal tract and skin [2] and are characterized by their wide morphological and functional heterogeneity [9]. In addition to these effector functions, eosinophils produce several Th1, Th2 and regulatory cytokines, such as IL-10 [10,11], which, in contrast to T cells, are stored within granules and promptly released upon activation [12]. Eosinophils also express MHCII and CD86 [10,13,14] and act as antigen-presenting cells [15]. Furthermore, eosinophils share with T cells expression of various receptors such as CD25 [16,17], CD4 [18], CD28 [10,14] and several members of the CD2 family, including 2B4 [19]. This wide array of molecules endows eosinophils with the ability to induce and regulate adaptive immunity. However, the early appearance of eosinophils in agnathans, predating the appearance of the classical adaptive immune system [20] and the expression by eosinophils of several receptors involved in innate immunity, such as formyl peptide receptor [21], protease-activated receptors [22,23] and TLR [24] further point toward a role for eosinophils in innate immunity. Eosinophils contribute to TLR-mediated immunity against viruses and mycobacteria [25,26]. Indeed, we recently showed that TLR-2- PLoS ONE | www.plosone.org 1 June 2009 | Volume 4 | Issue 6 | e5926