A Functional γδTCR/CD3 Complex Distinct from γδT Cells Is Expressed by Human Eosinophils

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 gamma delta T Cell Receptor (TCR) but not ab TCR. Surface expression of gamma delta TCR/CD3 is heterogeneous between eosinophil donors and inducible by mycobacterial ligands. Surface immunoprecipitation revealed expression of the full gamma delta TCR/CD3 complex. Real-time PCR amplification for CD3, gamma and delta TCR constant regions transcripts showed a significantly lower expression in eosinophils than in gamma delta T 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-gamma and TNF-alpha) was observed following activation by gamma delta TCR-specific agonists or by mycobacteria. These effects were inhibited by anti-gamma delta TCR blocking antibodies and antagonists. Moreover, gamma delta TCR/CD3 was involved in eosinophil cytotoxicity against tumor cells. Conclusions/Significance: Our results provide evidence that human eosinophils express a functional gamma delta TCR/CD3 with similar, but not identical, characteristics to gamma delta TCR from gamma delta T 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.