Benralizumab for PDGFRA-Negative Hypereosinophilic Syndrome.

BACKGROUND: Hypereosinophilic syndrome is a group of diseases defined by marked eosinophilia in blood or tissue and eosinophil-related clinical manifestations. Benralizumab is a monoclonal antibody against interleukin-5 receptor α, which is expressed on human eosinophils. METHODS: In this randomized, double-blind, placebo-controlled, phase 2 trial, we administered a series of three monthly subcutaneous injections of either benralizumab (at a dose of 30 mg) or placebo in 20 symptomatic patients who had PDGFRA-negative hypereosinophilic syndrome and an absolute eosinophil count of at least 1000 cells per cubic millimeter; all the patients were receiving stable therapy (drugs or dietary changes) for this disease. This regimen was followed by an open-label phase, during which the patient's background therapy could be tapered as tolerated, and an extension phase. The primary end point of the randomized phase was a reduction of at least 50% in the absolute eosinophil count at week 12. RESULTS: During the randomized phase, the primary end point occurred in more patients in the benralizumab group than in the placebo group (9 of 10 patients [90%] vs. 3 of 10 patients [30%], P = 0.02). During the open-label phase, clinical and hematologic responses were observed in 17 of 19 patients (89%) and were sustained for 48 weeks in 14 of 19 patients (74%); in the latter group, in 9 of 14 patients (64%), background therapies could be tapered. Bone marrow and tissue eosinophilia were also suppressed with benralizumab therapy. The most common drug-related adverse events, headache and an elevated lactate dehydrogenase level, occurred in 32% of the patients after the first dose of benralizumab and resolved within 48 hours in all patients. Other adverse events occurred with similar frequency in the two groups. Of the many potential predictors of response that were examined, only clinical disease subtype appeared to be associated with the initial response or relapse. CONCLUSIONS: In this small phase 2 trial, patients with PDGFRA-negative hypereosinophilic syndrome who received benralizumab for 12 weeks had lower absolute eosinophil counts than those who received placebo. During the open-label phase, clinical and hematologic responses were sustained for 48 weeks in 74% of the patients. Adverse events did not limit treatment. (Funded by the National Institute of Allergy and Infectious Diseases; ClinicalTrials.gov numbers, NCT00001406 and NCT02130882.).

Glucocorticoid-induced eosinopenia results from CXCR4-dependent bone marrow migration.

Glucocorticoids are considered first-line therapy in a variety of eosinophilic disorders. They lead to a transient, profound decrease in circulating human eosinophils within hours of administration. The phenomenon of glucocorticoid-induced eosinopenia has been the basis for the use of glucocorticoids in eosinophilic disorders, and it has intrigued clinicians for 7 decades, yet its mechanism remains unexplained. To investigate, we first studied the response of circulating eosinophils to in vivo glucocorticoid administration in 3 species and found that the response in rhesus macaques, but not in mice, closely resembled that in humans. We then developed an isolation technique to purify rhesus macaque eosinophils from peripheral blood and performed live tracking of zirconium-89-oxine-labeled eosinophils by serial positron emission tomography/computed tomography imaging, before and after administration of glucocorticoids. Glucocorticoids induced rapid bone marrow homing of eosinophils. The kinetics of glucocorticoid-induced eosinopenia and bone marrow migration were consistent with those of the induction of the glucocorticoid-responsive chemokine receptor CXCR4, and selective blockade of CXCR4 reduced or eliminated the early glucocorticoid-induced reduction in blood eosinophils. Our results indicate that glucocorticoid-induced eosinopenia results from CXCR4-dependent migration of eosinophils to the bone marrow. These findings provide insight into the mechanism of action of glucocorticoids in eosinophilic disorders, with implications for the study of glucocorticoid resistance and the development of more targeted therapies. The human study was registered at ClinicalTrials.gov as #NCT02798523.

A Randomized, Placebo-controlled, Double-blind Pilot Study of Single-dose Humanized Anti-IL5 Antibody (Reslizumab) for the Reduction of Eosinophilia Following Diethylcarbamazine Treatment of Loa loa Infection.

BACKGROUND: Diethylcarbamazine citrate (DEC) treatment of loiasis is complicated by adverse reactions that are correlated with the number of circulating microfilariae (mf). The cause of these reactions is unknown, but they are accompanied by a dramatic interleukin-5 (IL-5)-dependent increase in eosinophilia and evidence of eosinophil activation. METHODS: To explore the role of IL-5 driven eosinophilia in post-DEC reactions, 8 adults with confirmed loiasis and <5000 mf/mL blood were enrolled in a randomized, double-blind, placebo-controlled trial of the humanized anti-IL-5 antibody, reslizumab, (1.0 mg/kg IV) administered 3 to 7 days prior to initiation of DEC treatment (9 mg/kg/day for 21 days). The primary endpoint was the reduction in absolute eosinophil count (AEC) during the first week of DEC treatment. RESULTS: Baseline characteristics were comparable between the two groups. Single dose reslizumab lowered the AEC by 77% prior to initiation of DEC therapy (vs. 12% in the placebo group, P < .05). More importantly, AEC remained below baseline in the first week of DEC treatment in all subjects who received reslizumab and in none of the placebo subjects. Mf clearance occurred within 2 days of initiation of DEC in all 7 mf-positive subjects. Mild to moderate adverse events were seen in all 8 subjects and were not significantly different between the groups. CONCLUSIONS: In summary, although reslizumab was able to blunt peripheral eosinophilia post-DEC treatment in subjects with loiasis and had no effect on microfilarial clearance, the reduction in AEC appeared to have been insufficient to prevent post-treatment AEs.

Sialic acid-binding immunoglobulin-like lectin (Siglec) 8 in patients with eosinophilic disorders: Receptor expression and targeting using chimeric antibodies.

BACKGROUND: Sialic acid-binding immunoglobulin-like lectin (Siglec) 8 is selectively expressed on eosinophils, mast cells, and basophils and, when engaged on eosinophils, can cause cell death. OBJECTIVE: We sought to characterize surface and soluble Siglec-8 (sSiglec-8) levels in normal donors (NDs) and eosinophilic donors (EOs) and assess the efficacy of anti-Siglec-8 antibodies in inducing eosinophil cell death in vitro. METHODS: Eosinophil expression of Siglec-8 was assessed by using flow cytometry and quantitative PCR. Serum sSiglec-8 levels were measured by means of ELISA. Induction of eosinophil death by IgG4 (chimeric 2E2 IgG4) and afucosylated IgG1 (chimeric 2E2 IgG1 [c2E2 IgG1]) anti-Siglec-8 antibodies was evaluated in vitro by using flow cytometry and in vivo in humanized mice. RESULTS: Siglec-8 was consistently expressed on eosinophils from NDs and EOs and did not correlate with absolute eosinophil count or disease activity. sSiglec-8 levels were measurable in sera from most donors unrelated to absolute eosinophil counts or Siglec-8 surface expression. c2E2 IgG1 and chimeric 2E2 IgG4 were equally effective at inducing cell death (Annexin-V positivity) of purified eosinophils from NDs and EOs after overnight IL-5 priming. In contrast, killing of purified eosinophils without IL-5 was only seen in EOs, and natural killer cell-mediated eosinophil killing was seen only with c2E2 IgG1. Finally, treatment of humanized mice with anti-Siglec antibody led to robust depletion of IL-5-induced eosinophilia in vivo. CONCLUSIONS: Siglec-8 is highly expressed on blood eosinophils from EOs and NDs and represents a potential therapeutic target for eosinophilic disorders. Enhanced killing of eosinophils in the presence of IL-5 might lead to increased efficacy in patients with IL-5-driven eosinophilia.

Siglec-7 on peripheral blood eosinophils: Surface expression and function.

BACKGROUND: Siglec-7 is an inhibitory receptor (IR) expressed on human blood eosinophils. Whereas activation of other IRs, including Siglec-8 and CD300a, has been shown to downregulate eosinophil function, little is known about the role of Siglec-7 on human eosinophils. OBJECTIVE: To examine Siglec-7 expression and function in eosinophils from normal (ND) and eosinophilic (EO) donors. METHODS: Eosinophil expression of Siglec-7 was quantified by flow cytometry and quantitative PCR. Soluble Siglec-7 (sSiglec-7) levels were measured by ELISA in serum. The effect of Siglec-7 on eosinophil viability and degranulation was assessed in vitro by AnnexinV-FITC/7-AAD staining and by measuring GM-CSF-induced mediator release in culture supernatants. Signal transduction was studied by Western blot. RESULTS: Siglec-7 was expressed ex vivo on blood eosinophils from all eosinophilic and normal individuals studied. Siglec-7 surface, but not SIGLEC-7mRNA expression, was correlated with absolute eosinophil count (AEC). Siglec-7 was upregulated on purified eosinophils after in vitro stimulation with GM-CSF or IL-5. Serum sSiglec-7 was detectable in 133/144 subjects tested and correlated with AEC. Siglec-7 cross-linking inhibited GM-CSF-induced release of eosinophil peroxidase, TNF-α, and IL-8 (n = 7-8) but did not promote eosinophil apoptosis (n = 5). Finally, Siglec-7 cross-linking on GM-CSF-activated eosinophils induced phosphorylation of SHP-1 and de-phosphorylation of ERK1/2 and p38. CONCLUSIONS: Siglec-7 is constitutively expressed on human eosinophils and downmodulates eosinophil activation. Targeting of Siglec-7 on eosinophils might enhance treatment efficacy in eosinophil-driven disorders. Conversely, therapeutic interventions that inhibit Siglec-7 could have unanticipated consequences and promote eosinophilic inflammation.

Posttreatment Reactions After Single-Dose Diethylcarbamazine or Ivermectin in Subjects With Loa loa Infection.

Background: Severe adverse reactions have been observed in individuals with Loa loa infection treated with either diethylcarbamazine (DEC), the drug of choice for loiasis, or ivermectin (IVM), which is used in mass drug administration programs for control of onchocerciasis and lymphatic filariasis in Africa. In this study, posttreatment clinical and immunologic reactions were compared following single-dose therapy with DEC or IVM to assess whether these reactions have the same underlying pathophysiology. Methods: Twelve patients with loiasis and microfilarial counts <2000 mf/mL were randomized to receive single-dose DEC (8 mg/kg) or IVM (200 µg/kg). Clinical and laboratory assessments were performed at 4, 8, 24, 48, and 72 hours and 5, 7, 9, and 14 days posttreatment. Results: Posttreatment adverse events were similar following DEC or IVM, but peaked earlier in subjects who received DEC, consistent with a trend toward more rapid and complete microfilarial clearance in the DEC group. After a transient rise (post-IVM) or fall (post-DEC) in the first 24 hours posttreatment, the eosinophil count rose significantly in both groups, peaking at day 5 in the DEC group and day 9 in the IVM group. Serum interleukin 5 levels and eosinophil activation, as assessed by surface expression of CD69 and serum levels of eosinophil granule proteins, were increased posttreatment in both groups. Conclusions: Despite differences in eosinophil and lymphocyte counts during the first 24 hours posttreatment, the overall pattern of hematologic and immunologic changes suggest that posttreatment reactions following DEC and IVM share a common pathophysiology. Clinical Trials Registration: NCT01593722.

The eosinophil surface receptor epidermal growth factor-like module containing mucin-like hormone receptor 1 (EMR1): a novel therapeutic target for eosinophilic disorders.

BACKGROUND: Although several novel agents are currently in clinical trials for eosinophilic disorders, none has demonstrated efficacy in reducing blood and tissue eosinophilia in all subjects. Additional approaches are clearly needed. OBJECTIVE: We sought to explore the potential of the human eosinophil surface receptor epidermal growth factor-like module containing mucin-like hormone receptor 1 (EMR1) as a therapeutic target for eosinophilic disorders. METHODS: EMR1 expression was assessed in blood and bone marrow specimens from eosinophilic and healthy subjects, cell lines, CD34(+) cells differentiated in vitro, and tissue biopsy specimens by using flow cytometry, quantitative PCR, and immunostaining. Eosinophil targeting by a novel, humanized, afucosylated anti-EMR1 IgG1 was evaluated in vitro by using a natural killer cell-mediated killing assay and in vivo in cynomolgus monkeys. RESULTS: Analysis of blood and bone marrow cells from healthy and eosinophilic donors and in vitro-differentiated CD34(+) cells confirmed restriction of human EMR1 surface and mRNA expression to mature eosinophils. Tissue eosinophils also expressed EMR1. Although EMR1 was highly expressed on eosinophils from all subjects, surface expression was negatively correlated with absolute eosinophil counts (r = -0.46, P < .001), and soluble plasma levels correlated positively with absolute eosinophil counts (r = 0.69, P < .001), suggesting modulation of EMR1 in vivo. Nevertheless, afucosylated anti-EMR1 mAb dramatically enhanced natural killer cell-mediated killing of eosinophils from healthy and eosinophilic donors and induced a rapid and sustained depletion of eosinophils in monkeys. CONCLUSION: EMR1 expression is restricted to mature blood and tissue eosinophils. Targeting of eosinophils with afucosylated anti-EMR1 antibody shows promise as a treatment for eosinophilic disorders.

Involvement of eosinophils in the anti-tumor response.

Eosinophils have long been associated with allergy and parasitic infections. Today, they are considered as multifunctional leukocytes, which participate both in innate and adaptive immune response though the expression of various receptors and mediators. Although the tumor-associated eosinophilia is observed for a long time in many hematological and solid malignancies, with a generally good prognosis value, there is a lack of knowledge on the different mechanisms involved in this phenomenon. Moreover, the recent discovery in human eosinophils of different receptors and mediators, shared with lymphocytes and involved in anti-tumor defense, suggests that eosinophils can play a role in anti-tumoral immunity. We review in the present paper the current knowledge on epidemiology, recruitment, and mechanisms involved in the response of eosinophils toward tumors.

Human eosinophils exert TNF-α and granzyme A-mediated tumoricidal activity toward colon carcinoma cells.

Peripheral blood and tissue eosinophilia is a prominent feature in allergic diseases and helminth infections. In cancer patients, tumor-associated tissue eosinophilia is frequently observed. Tumor-associated tissue eosinophilia can be associated with a favorable prognosis, notably in colorectal carcinoma. However, underlying mechanisms of eosinophil contribution to antitumor responses are poorly understood. We have in this study investigated the direct interactions of human eosinophils with Colo-205, a colorectal carcinoma cell line, and show that eosinophils induce apoptosis and directly kill tumor cells. Using blocking Abs, we found that CD11a/CD18 complex is involved in the tumoricidal activity. Coculture of eosinophils with Colo-205 led to the release of eosinophil cationic protein and eosinophil-derived neurotoxin as well as TNF-α secretion. Moreover, eosinophils expressed granzyme A, which was released upon interaction with Colo-205, whereas cytotoxicity was partially inhibited by FUT-175, an inhibitor of trypsin-like enzymatic activity. Our data present the first demonstration, to our knowledge, that granzyme A is a cytotoxic mediator of the eosinophil protein arsenal, exerting eosinophil tumoricidal activity toward Colo-205, and provide mechanistic evidence for innate responses of eosinophil against tumor cells.

Rapid GPR183-mediated recruitment of eosinophils to the lung after Mycobacterium tuberculosis infection.

Influx of eosinophils into the lungs is typically associated with type II responses during allergy and fungal and parasitic infections. However, we previously reported that eosinophils accumulate in lung lesions during type I inflammatory responses to Mycobacterium tuberculosis (Mtb) in humans, macaques, and mice, in which they support host resistance. Here we show eosinophils migrate into the lungs of macaques and mice as early as one week after Mtb exposure. In mice this influx is CCR3 independent and instead requires cell-intrinsic expression of the oxysterol receptor GPR183, which is highly expressed on human and macaque eosinophils. Murine eosinophils interact directly with bacilli-laden alveolar macrophages, which upregulate the oxysterol-synthesizing enzyme Ch25h, and eosinophil recruitment is impaired in Ch25h-deficient mice. Our findings show that eosinophils are among the earliest cells from circulation to sense and respond to Mtb infection of alveolar macrophages and reveal a role for GPR183 in the migration of eosinophils into lung tissue.

TLR2-dependent eosinophil interactions with mycobacteria: role of alpha-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 Purification from Peripheral Blood of Rhesus Monkeys.

Eosinophils are granulocytes involved mainly in allergic inflammation and parasitic responses and constitute 1-5% of the circulating leukocytes in human healthy subjects. New immunotherapies targeting eosinophils have been developed and evaluated recently, and the availability of animal models that could mimic human eosinophil responses is important to consider. Differences in eosinophil biology and pathogenesis between humans and murine models have limited their utility in some settings. Isolation of viable eosinophils from rhesus macaque blood suitable for ex vivo and in vitro experimentation could provide a valuable tool for the study of eosinophil-targeted therapies and for the exploration of eosinophilic associated responses. Here, a new technique for the isolation of human eosinophils from rhesus macaque blood by negative selection from whole blood is described.

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

BACKGROUND: Eosinophils 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. OBJECTIVE: The ability of eosinophils to promote AHR and lung inflammation independently of lymphocytes was investigated. METHODS: Adoptive 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. RESULTS: Adoptively 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. CONCLUSIONS: These 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.

[Eosinophil: a new effector of innate immunity?]. / L'éosinophile : nouvel acteur de la réponse immunitaire innée ?

The eosinophil leukocyte has long been considered as a second class cell. It appears now that its functions extend far beyond solely the release of cytotoxic mediators involved in a protective role in some parasitic infections or in pathological manifestations during allergic diseases. The recent demonstration that eosinophils express innate immune receptors (TLR, gdTCR) and mediators (a-defensins), in addition to the numerous receptors involved in adaptive immunity, confers to eosinophils the potential to directly recognize danger signals including pathogens. Thus, both such a functional plasticity together with its strategic tissue localization indicate that eosinophils likely play a previously unsuspected role in anti-infectious response.

[New insights into hypereosinophilic syndromes]. / A la redécouverte des syndromes hyperéosinophiliques.

Hypereosinophilic syndrome (HES) is characterized by chronic unexplained eosinophilia with organ involvement. The concept of HES as a single disease entity is being challenged by the recent identification of multiple underlying molecular mechanisms. HES can directly affect the eosinophil lineage (often linked to a fusion gene FIP1L1-PDGFRA, and corresponding in this case to chronic eosinophilic leukemia), or the lymphoid lineage, where eosinophilia is secondary to expansion of a T cell subset overproducing interleukin-5, a cytokine involved in eosinophilopoiesis. These recent discoveries have legitimized the use of tyrosine kinase inhibitors such as imatinib, which, by inhibiting PDGFRA, have transformed the prognosis of chronic eosinophilic leukemia, and also the use of monoclonal anti-IL-5 antibodies, which are promising treatment for steroid-dependent HES.

[Functions of eosinophil granulocytes: from anti-parasite immunity to anti-tumoral potential]. / Fonctions des polynucléaires eosinophiles: de l'immunité anti-parasitaire aux potentialités anti tumorales.

Eosinophils have long been considered simply as effectors of adaptive immune responses during parasitic infections and inflammatory processes. Their role in allergic manifestations and mucosal responses is mediated by membrane receptors that allow them to interact with IgE and IgA antibodies. The recent demonstration that human eosinophils express innate immune receptors suggests that they may also play a role in antitumoral immune surveillance. Experimental evidence shows that human eosinophils have tumoricidal potential, in synergy with other effector cells, notably by releasing cytotoxic molecules.

Innate immune function of eosinophils: from antiparasite to antitumor cells.

Eosinophils are multifunctional leukocytes classically described as being involved in helminth parasitic infections and allergic diseases. Previously restricted to an exclusive role in the release of cytotoxic mediators, they are now also considered to be immunoregulatory cells and potential effectors in innate immune responses. Eosinophils are mainly found in tissues, so specific procedures are needed for their isolation from venous blood and for functional assays. Murine models are very useful for the dissection of eosinophil physiology in vivo. But murine eosinophils significantly differ from human ones. A complete understanding of eosinophil biology therefore requires comparative study of eosinophils from different mammalian species. We summarize here the main experimental protocols used to study human, mouse, and rat eosinophil biology. We focus on technical improvements of existing methods that optimize purification and in vitro functional studies of eosinophils.

Transcript- and protein-level analyses of the response of human eosinophils to glucocorticoids.

Glucocorticoids are first-line agents for the treatment of many eosinophil-associated disorders; however, their effects on human eosinophils remain poorly understood. To gain an unbiased, genome-wide view of the early transcriptional effects of glucocorticoids on human eosinophils in vivo, RNA sequencing was performed on purified blood eosinophils obtained before and 30, 60, and 120 minutes after administration of a single dose of oral prednisone (1 mg/kg) to three unrelated healthy subjects with hypereosinophilia of unknown significance. The resulting dataset is of high quality and suitable for differential expression analysis. Flow cytometry and qPCR were then performed on three additional cohorts of human subjects, to validate the key findings at the transcript and protein levels. The resulting datasets provide a resource for understanding the response of circulating human eosinophils to glucocorticoid administration.

Biologic therapies targeting eosinophils: current status and future prospects.

The recent explosion in the number of biologic therapies in clinical development for the treatment of eosinophilic disorders is unprecedented. As these agents become available for clinical use, the selection of the most appropriate agent for a given patient will become increasingly complicated. The aims of this review were 2-fold: (1) to present the lessons learned from clinical trials using the first generation of eosinophil-targeted biologics (anti-IL-5 antibodies) and (2) to discuss the advantages and potential limitations of currently available and novel targeted therapies to treat eosinophilic disorders.

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

The 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 0.35 G/L (range, 0.01-28.3), with a clonal TCRγδ 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) (n = 18) 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.