Fanny Legrand

TLR2-dependent eosinophil interactions with mycobacteria: Role of α-defensins

Peripheral blood and tissue eosinophilia are a prominent feature in allergic diseases and during helminth infections. Eosinophil recruitment also frequently occurs upon mycobacterial infections, particularly in lung granuloma. However, the mechanism by which eosinophils interact with mycobacteria remains largely unknown. Because eosinophils recently have been shown to be involved in innate immune responses, we investigated the direct interactions of eosinophils with Mycobacterium bovis BCG as a study model. We show that live BCG attracts human eosinophils and induces reactive oxygen species (ROS) synthesis, granule protein release, and tumor necrosis factor (TNF)-alpha secretion. Using anti-TLR2 neutralizing antibodies before exposure of eosinophils to BCG, we showed a critical role of TLR2 signaling in ROS and eosinophil peroxidase release. BCG-induced eosinophil activation is mediated through the p38 mitogen-activated protein (MAP) kinase and nuclear factor (NF)-kappaB pathways. In addition, a mycobacterial wall component, lipomannan, induced a TLR2-dependent eosinophil activation. In addition, we showed that eosinophils express and produce alpha-defensins upon stimulation with BCG and lipomannan and that alpha-defensins could inhibit mycobacterial growth in synergy with eosinophil cationic protein. These results suggest a role for human eosinophils as direct effectors in TLR2-mediated innate immunity against mycobacteria and confer to these cells potent cytotoxic functions through defensin and eosinophil cationic protein production.

Eosinophil-derived IFN-γ induces airway hyperresponsiveness and lung inflammation in the absence of lymphocytes

BACKGROUNDnEosinophils are key players in T(H)2-driven pathologies, such as allergic lung inflammation. After IL-5- and eotaxin-mediated tissue recruitment, they release several cytotoxic and inflammatory mediators. However, their exact contribution to asthma remains controversial. Indeed, in human subjects anti-IL-5 treatment inhibits eosinophilia but not antigen-induced airway hyperresponsiveness (AHR). Likewise, lung fibrosis is abrogated in 2 strains of eosinophil-deficient mice, whereas AHR is inhibited in only one of them. Finally, eosinophils have been shown to attract T(H)2 lymphocytes at the inflammatory site.nnnOBJECTIVEnThe ability of eosinophils to promote AHR and lung inflammation independently of lymphocytes was investigated.nnnMETHODSnAdoptive transfers of resting or activated eosinophils from IL-5 transgenic mice were performed into naive BALB/c mice, mice with severe combined immunodeficiency, and IFN-gamma-deficient BALB/c recipients.nnnRESULTSnAdoptively transferred eosinophils induced lung inflammation, fibrosis, collagen deposition, and AHR not only in BALB/c mice but also in recipient mice with severe combined immunodeficiency. Surprisingly, IFN-gamma expression was increased in lungs from eosinophil-transferred animals. Furthermore, IFN-gamma neutralization in recipients partially inhibited eosinophil-induced AHR. Moreover, IFN-gamma-deficient eosinophils or eosinophils treated with a blocking anti-IFN-gamma receptor antibody failed to induce AHR in IFN-gamma-deficient recipients. Finally, in vitro and at low concentrations, IFN-gamma increased eosinophil peroxidase release, potentiated chemotaxis, and prolonged survival, suggesting the existence of an autocrine mechanism.nnnCONCLUSIONSnThese results support the important and previously unsuspected contribution of eosinophils to lung inflammation independently of lymphocytes through production of IFN-gamma, the prototypical T(H)1 cytokine.

The Spectrum of FIP1L1-PDGFRA-Associated Chronic Eosinophilic Leukemia: New Insights Based on a Survey of 44 Cases

AbstractImatinib is the treatment of choice for FIP1L1/PDGFRA (F/P)-associated chronic eosinophilic leukemia (F/P+ CEL), but its optimal dosing, duration, and possibility of discontinuation are still a matter of debate. A retrospective multicenter study was conducted with 44 F/P+ CEL patients identified in the French Eosinophil Network and treated with imatinib. The most frequently involved systems were skin (57%), spleen (52%), and lung (45%), and eosinophilic heart disease was observed in 15 patients (34%). Complete hematologic response (CHR) was obtained in all patients, and complete molecular response (CMR) in 95% of patients (average initial imatinib dose, 165 mg/d). For 29 patients the imatinib dose was tapered with a maintenance dose of 58 mg/d (±34 mg/d), allowing sustained CHR and CMR. None of the patients developed resistance during a median follow-up of 52.3 months (range, 1.4–97.4 mo). Imatinib was stopped in 11 patients; 6 of the patients subsequently relapsed, but 5 remained in persistent CHR or CMR (range, 9–88 mo). These results confirm that an initial low-dose regimen of imatinib (100 mg/d) followed by a lower maintenance dose can be efficient for obtaining long-term CHR and CMR. Our data also suggest that imatinib can be stopped in some patients without molecular relapse.

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

The lymphoid variant of hypereosinophilic syndrome: study of 21 patients with CD3-CD4+ aberrant T-cell phenotype.

AbstractThe CD3-CD4+ aberrant T-cell phenotype is the most described in the lymphoid variant of hypereosinophilic syndrome (L-HES), a rare form of HES. Only a few cases have been reported, and data for these patients are scarce. To describe characteristics and outcome of CD3-CD4+ L-HES patients, we conducted a national multicentric retrospective study in the French Eosinophil Network. All patients who met the recent criteria of hypereosinophilia (HE) or HES and who had a persistent CD3-CD4+ T-cell subset on blood T-cell phenotyping were included. Clinical and laboratory data were retrospectively collected by chart review. CD3-CD4+ L-HES was diagnosed in 21 patients (13 females, median age 42 years [range, 5–75 yr]). Half (48%) had a history of atopic manifestations. Clinical manifestations were dermatologic (81%), superficial adenopathy (62%), rheumatologic (29%), gastrointestinal (24%), pulmonary (19%), neurologic (10%), and cardiovascular (5%). The median absolute CD3-CD4+ T-cell count was 0.35u2009G/L (range, 0.01–28.3), with a clonal TCR&ggr;&dgr; rearrangement in 76% of patients. The mean follow-up duration after HES diagnosis was 6.9 ± 5.1 years. All patients treated with oral corticosteroids (CS) (nu2009=u200918) obtained remission, but 16 required CS-sparing treatments. One patient had a T-cell lymphoma 8 years after diagnosis, and 3 deaths occurred during follow-up.In conclusion, clinical manifestations related to CD3-CD4+ T cell-associated L-HES are not limited to skin, and can involve all tissue or organs affected in other types of HE. Contrary to FIP1L1-PDGFRA chronic eosinophilic leukemia patients, CS are always effective in these patients, but CS-sparing treatments are frequently needed. The occurrence of T-cell lymphoma, although rare in our cohort, remains a major concern during follow-up.

CR3-dependent negative regulation of human eosinophils by Mycobacterium bovis BCG lipoarabinomannan.

Eosinophils have recently been shown to participate in innate immune responses against mycobacteria. We have investigated whether Mycobacterium bovis BCG regulate the human eosinophil immune response. A negative correlation between mycobacteria internalization and eosinophil activation was observed. In addition, mannose-capped lipoarabinomannan from M. bovis BCG (ManLAM) failed to induce a significant release of eosinophil peroxidase and TNF-α. Noteworthy, ManLAM exhibited a potent inhibitory effect on eosinophil peroxidase release by TLR2-activated eosinophils involving the complement receptor-3 molecule and the phosphatidylinositol-3 kinase pathway. ManLAM, generally present in pathogenic mycobacteria, plays an important role in modulating eosinophil-dependent immune response.