Lymphocytic variant of hypereosinophilic syndrome: A report of seven cases from a single institution.

BACKGROUND: Lymphocytic variant of hypereosinophilic syndrome (L-HES) is a subtype of HES driven by cytokines produced by clonal T-cells. Due to the rarity of its occurrence and challenges in diagnosis, this subtype of HES is under recognized. METHODS AND RESULTS: We report seven patients with L-HES, diagnosed from a group of 136 patients who were referred to our institution for the work-up of hypereosinophilia. The clinical presentation, symptoms and signs were heterogeneous and uncharacteristic; indistinguishable from idiopathic HES. Flow cytometry immunophenotypic analysis revealed aberrant T-cells in all patients, with a Th2 immunophenotype, CD2 + CD3-CD4 + CD5 + CD7dim+/-CD8- in six of seven (86%) cases. CD10 was partially expressed in one of seven (14%) cases, and clonal TCR gene rearrangement was detected by PCR in five of seven (71%) patients. All patients were treated with corticosteroids and two of seven (29%) patients received anti-IL5 antibody therapy. With a median follow-up time of 7.5 years (2.3-14.1 years), one (11%) patient developed peripheral T-cell lymphoma 6.1 years after the initial diagnosis of L-HES and responded well to chemotherapy. All patients were alive at the last follow-up. CONCLUSION: In conclusion, a combination of flow cytometry immunophenotyping and molecular analysis allows the identification of aberrant T-cells, facilitating a diagnosis of L-HES in patients with eosinophilia. A correct diagnosis is essential for the proper management of these patients.

S100A8 and S100A9 Promote Apoptosis of Chronic Eosinophilic Leukemia Cells.

S100A8 and S100A9 function as essential factors in inflammation and also exert antitumor or tumorigenic activity depending on the type of cancer. Chronic eosinophilic leukemia (CEL) is a rare hematological malignancy having elevated levels of eosinophils and characterized by the presence of the FIP1L1-PDGFRA fusion gene. In this study, we examined the pro-apoptotic mechanisms of S100A8 and S100A9 in FIP1L1-PDGFRα+ eosinophilic cells and hypereosinophilic patient cells. S100A8 and S100A9 induce apoptosis of the FIP1L1-PDGFRα+ EoL-1 cells via TLR4. The surface TLR4 expression increased after exposure to S100A8 and S100A9 although total TLR4 expression decreased. S100A8 and S100A9 suppressed the FIP1L1-PDGFRα-mediated signaling pathway by downregulating FIP1L1-PDGFRα mRNA and protein expression and triggered cell apoptosis by regulating caspase 9/3 pathway and Bcl family proteins. S100A8 and S100A9 also induced apoptosis of imatinib-resistant EoL-1 cells (EoL-1-IR). S100A8 and S100A9 blocked tumor progression of xenografted EoL-1 and EoL-1-IR cells in NOD-SCID mice and evoked apoptosis of eosinophils derived from hypereosinophilic syndrome as well as chronic eosinophilic leukemia. These findings may contribute to a progressive understanding of S100A8 and S100A9 in the pathogenic and therapeutic mechanism of hematological malignancy.

Targeted Anti-IL-5 Therapies and Future Therapeutics for Hypereosinophilic Syndrome and Rare Eosinophilic Conditions.

Eosinophilic inflammation is a component of many atopic diseases such as asthma, and biologics targeting eosinophils have been shown to be effective in subsets of these patients. However, there also are conditions in which eosinophils are the key inflammatory cells responsible for driving tissue damage. In these eosinophilic diseases such as hyper-eosinophilic syndrome, eosinophilic esophagitis, and eosinophilic granulomatosis with polyangiitis (EGPA), the development of biologics inhibiting eosinophilic inflammation have offered targeted therapeutic strategies for patients that have not responded well to typical first line drugs, which often have significant adverse side effects with poor disease modification or recurrent relapse with significant morbidity. IL-5 has long been recognized as the key inflammatory cytokine involved in the priming and survival of eosinophils and their proliferation and maturation in eosinophilic disease. There are a number of trials and case series demonstrating the immunomodulatory benefits of anti-IL-5 therapies in these diseases with good clinical responses. Yet, due to the heterogeneity and rarity of these conditions, anti-IL-5 therapies have not resulted in disease remission for all patients. Clearly, further research into the use of anti-IL-5 therapies in various eosinophilic diseases is needed and ongoing investigation into other immune mechanisms underlying chronic eosinophilic diseases may provide alternative therapies for these challenging conditions.

LCP1 triggers mTORC2/AKT activity and is pharmacologically targeted by enzastaurin in hypereosinophilia.

Hypereosinophilia (HE) is caused by a variety of disorders, ranging from parasite infections to autoimmune diseases and cancer. Only a small proportion of HE cases are clonal malignancies, and one of these, the group of eosinophilia-associated tyrosine kinase fusion-driven neoplasms, is sensitive to tyrosine kinase inhibitors, while most subtypes lack specific treatment. Eosinophil functions are highly dependent on actin polymerization, promoting priming, shape change, and infiltration of inflamed tissues. Therefore, we investigated the role of the actin-binding protein lymphocyte cytosolic protein 1 (LCP1) in malignant and nonmalignant eosinophil differentiation. We use the protein kinase C-ß (PKCß) selective inhibitor enzastaurin (Enza) to dephosphorylate and inactivate LCP1 in FIP1L1-platelet-derived growth factor receptor α (PDGFRA)-positive Eol-1 cells, and this was associated with reduced proliferation, metabolic activity, and colony formation as well as enhanced apoptosis and impaired migration. While Enza did not alter FIP1L1-PDGFRA-induced signal transducer and activator of transcription 3 (STAT3), STAT5, and ERK1/2 phosphorylation, it inhibited STAT1Tyr701 and AKTSer473 (but not AKTThr308 ) phosphorylation, and short hairpin RNA knockdown experiments confirmed that this process was mediated by LCP1 and associated mammalian target of rapamycin complex 2 (mTORC2) activity loss. Homeobox protein HoxB8 immortalized murine bone marrow cells showed impaired eosinophilic differentiation upon Enza treatment or LCP1 knockdown. Furthermore, Enza treatment of primary HE samples reduced eosinophil differentiation and survival. In conclusion, our data show that HE involves active LCP1, which interacts with mTOR and triggers mTORC2 activity, and that the PKCß inhibitor Enza as well as targeting of LCP1 may provide a novel treatment approach to hypereosinophilic disorders.

JAK2 ex13InDel drives oncogenic transformation and is associated with chronic eosinophilic leukemia and polycythemia vera.

The V617F mutation in the JH2 domain of Janus kinase 2 (JAK2) is an oncogenic driver in several myeloproliferative neoplasms (MPNs), including essential thrombocythemia, myelofibrosis, and polycythemia vera (PV). Other mutations in JAK2 have been identified in MPNs, most notably exon 12 mutations in PV. Here, we describe a novel recurrent mutation characterized by a common 4-amino-acid deletion and variable 1-amino-acid insertion (Leu583-Ala586DelInsSer/Gln/Pro) within the JH2 domain of JAK2. All 4 affected patients had eosinophilia, and both patients with Leu583-Ala586DelInsSer fulfilled diagnostic criteria of both PV and chronic eosinophilic leukemia (CEL). Computational and functional studies revealed that Leu583-Ala586DelInsSer (herein referred to as JAK2ex13InDel) deregulates JAK2 through a mechanism similar to JAK2V617F, activates signal transducer and activator of transcription 5 and extracellular signal-regulated kinase, and transforms parental Ba/F3 cells to growth factor independence. In contrast to JAK2V617F, JAK2ex13InDel does not require an exogenous homodimeric type 1 cytokine receptor to transform Ba/F3 cells and is capable of activating ß common chain family cytokine receptor (interleukin-3 receptor [IL-3R], IL-5R, and granulocyte-macrophage colony stimulating factor receptor) signaling in the absence of ligand, with the maximum effect observed for IL-5R, consistent with the clinical phenotype of eosinophilia. Recognizing this new PV/CEL-overlap MPN has significant clinical implications, as both PV and CEL patients are at high risk for thrombosis, and concomitant cytoreduction of red cells, neutrophils, and eosinophils may be required for prevention of thromboembolic events. Targeted next-generation sequencing for genes recurrently mutated in myeloid malignancies in patients with unexplained eosinophilia may reveal additional cases of Leu583-Ala586DelInsSer/Gln/Pro, allowing for complete characterization of this unique MPN.

Activity of 2,6,9-trisubstituted purines as potent PDGFRα kinase inhibitors with antileukaemic activity.

Receptor tyrosine kinase PDGFRα is often constitutively activated in various tumours and is regarded as a drug target. Here, we present a collection of 2,6,9-trisubstituted purines with nanomolar potency against PDGFRα and strong and selective cytotoxicity in the human eosinophilic leukaemia cell line EOL-1 that expresses the FIP1L1-PDGFRA oncogene. In treated EOL-1 cells, the example compound 14q inhibited the autophosphorylation of PDGFRα and the phosphorylation of STAT3 and ERK1/2. Interestingly, we observed pronounced and even increased effects of 14q on PDGFRα and some of its downstream signalling pathways after drug washout. In accordance with suppressed PDGFRα signalling, treated cells were arrested in the G1 phase of the cell cycle and eventually underwent apoptosis. Our results show that substituted purines can be used as specific modulators of eosinophilic leukaemia.

Characterization of a mouse model of hypereosinophilia-associated heart disease.

Hypereosinophilic syndrome is characterized by sustained and marked eosinophilia leading to tissue damage and organ dysfunction. Morbidity and mortality occur primarily due to cardiac and thromboembolic complications. Understanding the cause and mechanism of disease would aid in the development of targeted therapies with greater efficacy and fewer side effects. We discovered a spontaneous mouse mutant in our colony with a hypereosinophilic phenotype. Mice develop peripheral blood eosinophilia; infiltration of lungs, spleen, and heart by eosinophils; and extensive myocardial damage and remodeling. This ultimately leads to heart failure and premature death. Histopathological assessment of the hearts revealed a robust inflammatory infiltrate composed primarily of eosinophils and B-lymphocytes, associated with myocardial damage and replacement fibrosis, consistent with eosinophilic myocarditis. In many cases, hearts showed dilatation and thinning of the right ventricular wall, suggestive of an inflammatory dilated cardiomyopathy. Most mice showed atrial thrombi, which often filled the chamber. Protein expression analysis revealed overexpression of chemokines and cytokines involved in innate and adaptive immunity including IL-4, eotaxin, and RANTES. Disease could be transferred to wild-type mice by adoptive transfer of splenocytes from affected mice, suggesting a role for the immune system. In summary, the pathologies observed in the mutant lines are reminiscent of those seen in patients with hypereosinophilia, where cardiac-related morbidities, like congestive heart failure and thrombi, are the most common causes of death. As such, our model provides an opportunity to test mechanistic hypotheses and develop targeted therapies.NEW & NOTEWORTHY This article describes a new model of heart disease in hypereosinophilia. The model developed as a spontaneous mouse mutant in the colony and is characterized by peripheral blood eosinophilia and infiltration of lungs, spleen, and heart by eosinophils. In the heart, there is extensive myocardial damage, remodeling, fibrosis, and thrombosis, leading to heart failure and death. The immune microenvironment is one of increased innate and adaptive immunity, including Th1 and Th2 cytokines/chemokines. Finally, adoptive transfer of splenocytes transfers disease to recipient mice. In summary, this model provides an opportunity to test mechanistic hypotheses and develop targeted therapies for this rare but devastating disease.

Discovery of 4-((N-(2-(dimethylamino)ethyl)acrylamido)methyl)-N-(4-methyl-3-((4-(pyridin-3-yl)pyrimidin-2-yl)amino)phenyl)benzamide (CHMFL-PDGFR-159) as a highly selective type II PDGFRα kinase inhibitor for PDGFRα driving chronic eosinophilic leukemia.

Through exploration of the non-highly conserved allosteric hydrophobic pocket generated by DFG-out shifting in the inactive conformation, we discovered a highly selective type II PDGFRα kinase inhibitor 15i (CHMFL-PDGFRα-159), which exhibited strong potency against purified PDGFRα (IC50: 132 nM) but not structurally similar PDGFRß, ABL, c-KIT and VEGFR2 kinases. In addition, it displayed a high selectivity profile (S score (10) = 0.02) at the concentration of 1 µM among 468 kinases/mutants in the KINOMEscan profiling. X-ray crystal structure of 15i in complex with PDGFRα revealed a distinct binding feature in the allosteric hydrophobic pocket which might help to expand the diversity of type II kinase inhibitors. Compound 15i potently inhibited the proliferation of PDGFRα driving Chronic Eosinophilic Leukemia (CEL) cell line EOL-1 through strong blockage of PDGFRα mediated signaling pathways, arresting cell cycle progression, and induction of apoptosis. Furthermore, compound 15i effectively suppressed the EOL-1 tumor progression in the xenograft model and increased the survival rate in the engraftment tumor model.

Leukemogenic kinase FIP1L1-PDGFRA and a small ubiquitin-like modifier E3 ligase, PIAS1, form a positive cross-talk through their enzymatic activities.

Fusion tyrosine kinases play a crucial role in the development of hematological malignancies. FIP1L1-PDGFRA is a leukemogenic fusion kinase that causes chronic eosinophilic leukemia. As a constitutively active kinase, FIP1L1-PDGFRA stimulates downstream signaling molecules, leading to cellular proliferation and the generation of an anti-apoptotic state. Contribution of the N-terminal FIP1L1 portion is necessary for FIP1L1-PDGFRA to exert its full transforming activity, but the underlying mechanisms have not been fully characterized. We identified PIAS1 as a FIP1L1-PDGFRA association molecule by yeast two-hybrid screening. Our analyses indicate that the FIP1L1 portion of FIP1L1-PDGFRA is required for efficient association with PIAS1. As a consequence of the association, FIP1L1-PDGFRA phosphorylates PIAS1. Moreover, the kinase activity of FIP1L1-PDGFRA stabilizes PIAS1. Therefore, PIAS1 is one of the downstream targets of FIP1L1-PDGFRA. Moreover, we found that PIAS1, as a SUMO E3 ligase, sumoylates and stabilizes FIP1L1-PDGFRA. In addition, suppression of PIAS1 activity by a knockdown experiment resulted in destabilization of FIP1L1-PDGFRA. Therefore, FIP1L1-PDGFRA and PIAS1 form a positive cross-talk through their enzymatic activities. Suppression of sumoylation by ginkgolic acid, a small molecule compound inhibiting a SUMO E1-activating enzyme, also destabilizes FIP1L1-PDGFRA, and while the tyrosine kinase inhibitor imatinib suppresses FIP1L1-PDGFRA-dependent cell growth, ginkgolic acid or siRNA of PIAS1 has a synergistic effect with imatinib. In conclusion, our results suggest that sumoylation by PIAS1 is a potential target in the treatment of FIP1L1-PDGFRA-positive chronic eosinophilic leukemia.

The Eosinophil in Health and Disease: from Bench to Bedside and Back.

Historically, eosinophils have been considered as end-stage cells involved in host protection against parasitic infection and in the mechanisms of hypersensitivity. However, later studies have shown that this multifunctional cell is also capable of producing immunoregulatory cytokines and soluble mediators and is involved in tissue homeostasis and modulation of innate and adaptive immune responses. In this review, we summarize the biology of eosinophils, including the function and molecular mechanisms of their granule proteins, cell surface markers, mediators, and pathways, and present comprehensive reviews of research updates on the genetics and epigenetics of eosinophils. We describe recent advances in the development of epigenetics of eosinophil-related diseases, especially in asthma. Likewise, recent studies have provided us with a more complete appreciation of how eosinophils contribute to the pathogenesis of various diseases, including hypereosinophilic syndrome (HES). Over the past decades, the definition and criteria of HES have been evolving with the progress of our understanding of the disease and some aspects of this disease still remain controversial. We also review recent updates on the genetic and molecular mechanisms of HES, which have spurred dramatic developments in the clinical strategies of diagnosis and treatment for this heterogeneous group of diseases. The conclusion from this review is that the biology of eosinophils provides significant insights as to their roles in health and disease and, furthermore, demonstrates that a better understanding of eosinophil will accelerate the development of new therapeutic strategies for patients.

Nasal lavage levels of granulocyte-macrophage colony-stimulating factor and chronic nasal hypereosinophilia.

BACKGROUND: The aim of the present study was to measure levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) in nasal lavage of patients affected by chronic eosinophilic sinonasal inflammation to clarify the relationship with eosinophilic tissue infiltration and clinical features. METHODS: Between November 2012 and June 2013, we selected 70 patients with chronic eosinophilic inflammation (average age 41.8 years) who were classified into the following groups: persistent allergic rhinitis (group 1), noninfectious non-allergic rhinitis with eosinophilia syndrome (group 2) and chronic rhinosinusitis with polyps (group 3). Finally, we enrolled 20 healthy subjects as controls (group 4). All patients underwent symptoms score questionnaire based on a visual analogue scale, nasal endoscopy and/or computed tomography (CT) scan, and allergy testing. Nasal cytology by scraping of the mucosa and GM-CSF assays in nasal lavage were performed in all subjects. RESULTS: Detectable levels of GM-CSF were found in 34 of 70 (48.57%) patients, with an average concentration of 2.67 ± 0.8 pg/mL, whereas in controls only 1 of 20 individuals showed detectable GM-CSF levels. Eosinophil infiltration was significantly higher in patients with detectable GM-CSF compared to those with undetectable levels (49.4% vs 39.2%, respectively; p < 0.05). Furthermore, significant weakly-moderate correlation was found between GM-CSF levels and percentage of eosinophil infiltration in tissue (p < 0.05). Correlation between symptom scores and GM-CSF levels was significant only in group 2, which showed higher average concentrations of GM-CSF compared to groups 1 and 3 (2.9 pg/mL vs 1.6 pg/mL and 1.8 pg/mL, respectively; p < 0.05). CONCLUSION: Our data confirm that GM-CSF is more frequently detectable in nasal lavages of patients affected by chronic sinonasal eosinophilic inflammation than in controls. Statistical analyses revealed a significant weakly-moderate correlation between GM-CSF levels in nasal lavage of all patients and percentage of eosinophil infiltration of nasal mucosa.

CD3-CD4+ lymphoid variant of hypereosinophilic syndrome: nodal and extranodal histopathological and immunophenotypic features of a peripheral indolent clonal T-cell lymphoproliferative disorder.

The CD3(-)CD4(+) lymphoid variant of hypereosinophilic syndrome is characterized by hypereosinophilia and clonal circulating CD3(-)CD4(+) T cells. Peripheral T-cell lymphoma has been described during this disease course, and we observed in our cohort of 23 patients 2 cases of angio-immunoblastic T-cell lymphoma. We focus here on histopathological (n=12 patients) and immunophenotypic (n=15) characteristics of CD3(-)CD4(+) lymphoid variant of hypereosinophilic syndrome. Atypical CD4(+) T cells lymphoid infiltrates were found in 10 of 12 CD3(-)CD4(+) L-HES patients, in lymph nodes (n=4 of 4 patients), in skin (n=9 of 9) and other extra-nodal tissues (gut, lacrymal gland, synovium). Lymph nodes displayed infiltrates limited to the interfollicular areas or even an effacement of nodal architecture, associated with proliferation of arborizing high endothelial venules and increased follicular dendritic cell meshwork. Analysis of 2 fresh skin samples confirmed the presence of CD3(-)CD4(+) T cells. Clonal T cells were detected in at least one tissue in 8 patients, including lymph nodes (n=4 of 4): the same clonal T cells were detected in blood and in at least one biopsy, with a maximum delay of 23 years between samples. In the majority of cases, circulating CD3(-)CD4(+) T cells were CD2(hi) (n=9 of 14), CD5(hi) (n=12 of 14), and CD7(-)(n=4 of 14) or CD7(low) (n=10 of 14). Angio-immunoblastic T-cell lymphoma can also present with CD3(-)CD4(+) T cells; despite other common histopathological and immunophenotypic features, CD10 expression and follicular helper T-cell markers were not detected in lymphoid variant of hypereosinophilic syndrome patients, except in both patients who developed angio-immunoblastic T-cell lymphoma, and only at T-cell lymphoma diagnosis. Taken together, persistence of tissular clonal T cells and histopathological features define CD3(-)CD4(+) lymphoid variant of hypereosinophilic syndrome as a peripheral indolent clonal T-cell lymphoproliferative disorder, which should not be confused with angio-immunoblastic T-cell lymphoma.

[EOSINOPHILIC DISORDERS OF GASTROINTESTINAL TRACT].

Pathological eosinophilic infiltration of the various parts of the gastrointestinal tract (GIT) is a marker of a wide range of diseases, combined into three groups: eosinophil-associated gastrointestinal diseases (primary gastrointestinal eosinophilia), gastrointestinal disorders within the hypereosinophilic syndrome, gastrointestinal eosinophilia, developing, for obvious reasons. The article provides an overview of foreing and domestic literature about ethiopathogenesis, diagnosis and treatment methods of these three groups of gastrointestinal eosinophilia.

Enhanced tissue factor expression by blood eosinophils from patients with hypereosinophilia: a possible link with thrombosis.

Thrombotic risk is increased in eosinophil-mediated disorders, and several hypotheses have been proposed to link eosinophilia and thrombosis. In particular, eosinophils have been described as source of tissue factor (TF), the main initiator of blood coagulation; however, this aspect is still controversial. This study was aimed to evaluate whether TF expression varies in eosinophils isolated from normal subjects and patients with different hypereosinophilic conditions. Eosinophils were immunologically purified from peripheral blood samples of 9 patients with different hypereosinophilic conditions and 9 normal subjects. Western blot analysis and real-time polymerase chain reaction (RT-PCR) were performed to test eosinophil TF expression. For comparison, TF expression was evaluated in monocytes from blood donors and in human endothelial (ECV304) and fibroblast (IMR90) cell lines. Western blot analysis revealed a major band of 47,000 corresponding to native TF in homogenates of purified eosinophils with a higher intensity in the 9 patients than in the 9 controls (p<0.0001). According to RT-PCR cycle threshold (Ct), TF gene expression was higher in eosinophils from patients than in those from controls, median (range) 35.10 (19.45-36.50) vs 37.17 (35.33-37.87) (p = 0.002), and was particularly abundant in one patient with idiopathic hypereosinophilic syndrome and ischemic heart attacks (Ct: 19.45). TF gene expression was moderate in monocytes, Ct: 31.32 (29.82-33.49) and abundant in endothelial cells, Ct: 28.70 (27.79-29.57) and fibroblasts, Ct: 22.77 (19.22-25.05). Our results indicate that human blood eosinophils contain variable amounts of TF. The higher TF expression in patients with hypereosinophilic disorders may contribute to increase the thrombotic risk.

Apoptosis- and differentiation-inducing activities of jacaric acid, a conjugated linolenic acid isomer, on human eosinophilic leukemia EoL-1 cells.

Conjugated linolenic acids (CLNAs) are a group of naturally occurring positional and geometrical isomers of the C18 polyunsaturated essential fatty acid, linolenic acid (LNA), with three conjugated double bonds (C18:3). Although previous research has demonstrated the growth-inhibitory effects of CLNA on a wide variety of cancer cell lines in vitro, their action mechanisms and therapeutic potential on human myeloid leukemia cells remain poorly understood. In the present study, we found that jacaric acid (8Z,10E,12Z-octadecatrienoic acid), a CLNA isomer which is present in jacaranda seed oil, inhibited the in vitro growth of human eosinophilic leukemia EoL-1 cells in a time- and concentration-dependent manner. Mechanistic studies showed that jacaric acid triggered cell cycle arrest of EoL-1 cells at the G0/G1 phase and induced apoptosis of the EoL-1 cells, as measured by the Cell Death Detection ELISAPLUS kit, Annexin V assay and JC-1 dye staining. Notably, the jacaric acid-treated EoL-1 cells also underwent differentiation as revealed by morphological and phenotypic analysis. Collectively, our results demonstrated the capability of jacaric acid to inhibit the growth of EoL-1 cells in vitro through triggering cell cycle arrest and by inducing apoptosis and differentiation of the leukemia cells. Therefore, jacaric acid might be developed as a potential candidate for the treatment of certain forms of myeloid leukemia with minimal toxicity and few side effects.

Murine models of eosinophilic leukemia: a model of FIP1L1-PDGFRα initiated chronic eosinophilic leukemia/systemic mastocytosis.

Chronic eosinophilic leukemia (CEL) was distinguished from hypereosinophilic syndrome (HES) in the 2001 World Health Organization (WHO) criteria. Subsequently, the FIP1L1-PDGFRα (F/P) fusion tyrosine kinase was identified in patients with HES and found to be the most common clonal defect in CEL and the second most frequent mutation in systemic mastocytosis (SM). Introduction of F/P into bone marrow hematopoietic stem cells and progenitors has been used to establish murine models of F/P-myeloproliferative neoplasm and F/P-CEL. IL-5 overexpression and introduction of F/P is required to develop murine CEL. This F/P-CEL model is thought to be an accurate model of the clinical disease. Here we describe the method of F/P-CEL/SM model development and assessment.

Eosinophilia in mast cell disease.

Eosinophils and mast cells coexist in clonal and nonclonal disorders. The interplay between these cells is complex and not fully understood. Discussed are both allergic/nonclonal disorders in which both cell types are increased in number are likely to play a role in pathogenesis and clonal disorders in which both cell types are affected and play key roles in pathogenesis. Finally, some treatment options, keeping both disorders in mind, are discussed. Future directions in thinking about these disorders are also briefly explored.