Report of a Patient With Possible Process of Crystal Formation and Clinical Significance of a "Necrotic" Change

Langerhans cell histiocytosis is a rare neoplastic disorder characterized by the proliferation of Langerhans cells and often accompanied by eosinophil infiltration. Charcot-Leyden crystals, composed of galectin 10, are occasionally observed in Langerhans cell histiocytosis; however, histological images are rarely reported. We herein present a patient with Langerhans cell histiocytosis with Charcot-Leyden crystals and hexagonal crystals by describing the histologic and immunohistochemical features of a lymph node. A unique distribution of Charcot-Leyden crystals and hexagonal crystals was observed in this patient, shedding light on their possible formation process of the latter. We discuss the biological significance of eosinophilic abscesses in Langerhans cell histiocytosis and propose that these crystals may be linked to extracellular trap-cell death (ETosis). This example challenges the conventional characterization of "necrosis" in Langerhans cell histiocytosis and underscores the importance of recognizing ETosis as a potential mechanism involved in the pathogenesis of Langerhans cell histiocytosis. Further studies are underway to validate significance of these findings in a larger cohort of Langerhans cell histiocytosis patients.

Eosinophil extracellular traps in eosinophilic chronic rhinosinusitis induce Charcot-Leyden crystal formation and eosinophil recruitment

Eosinophil extracellular traps (EETs) are implicated in various eosinophil-associated diseases; however, their role in chronic rhinosinusitis (CRS) remains unclear. In the present study, 57 CRS patients were enrolled, and immunofluorescence was used to analyze EETs in eosinophilic (eCRS) and non-eosinophilic (Non-eCRS) tissues. MSD was used to examine IL-4, IL-5, and IL-13 concentrations in tissue homogenates. Charcot-Leyden crystals (CLCs) protein expression was detected in PMA, PMA+DNase I, and blank control eosinophils using ELISA. Eotaxin-3 mRNA and protein levels were measured in human nasal epithelial cells (HNECs) cultured with EETs, EETs+DNase I, DNase I, and unstimulated eosinophils using PCR and ELISA. EETs were significantly increased in eCRS tissues compared with Non-eCRS (P<0.001), and correlated with VAS and Lund-Mackay CT scores. IL-5 expression was related to EETs formation (r = 0.738, P<0.001). PMA-stimulated eosinophils exhibited higher CLCs protein levels (P<0.01). Co-culturing HNECs with EETs significantly increased eotaxin-3 mRNA and protein levels (P<0.0001, P<0.001) compared with other groups. The study suggests EETs formation is elevated in eCRS patients and is involved in CLCs formation and chemokine secretion, promoting eosinophilic inflammation.

Clonorchis sinensis infection in a non‑endemic area: A case report

Non-endemic Clonorchis sinensis infection is challenging to diagnose. The present study reports the case of a 40-year-old female patient with severe epigastric pain, initially suspected to be a liver lesion, who was admitted to The Affiliated Hospital of Zunyi Medical University (Zunyi, China). A combination of diagnostic procedures, including computed tomography and magnetic resonance imaging, revealed an abnormality in the left hepatic lobe. Postoperative evaluation and the epidemiologic history of the patient (consumption of raw fish slices) revealed characteristics of Clonorchis sinensis infection, including chronic bile duct inflammation and eosinophilic liver infiltration. The present case highlights the unexpected emergence of this disease outside of recognized endemic areas and advocates clinical vigilance. Even in non-endemic areas, individuals should be reminded not to eat raw fish and shrimp.

Ym1 protein crystals promote type 2 immunity

Spontaneous protein crystallization is a rare event, yet protein crystals are frequently found in eosinophil-rich inflammation. In humans, Charcot-Leyden crystals (CLCs) are made from galectin-10 (Gal10) protein, an abundant protein in eosinophils. Although mice do not encode Gal10 in their genome, they do form pseudo-CLCs, made from the chitinase-like proteins Ym1 and/or Ym2, encoded by Chil3 and Chil4 and made by myeloid and epithelial cells respectively. Here, we investigated the biological effects of pseudo-CLCs since their function is currently unknown. We produced recombinant Ym1 crystals which were shown to have identical crystal packing and structure by X-ray crystallography as in vivo native crystals derived from murine lung. When administered to the airways of mice, crystalline but not soluble Ym1 stimulated innate and adaptive immunity and acted as a type 2 immune adjuvant for eosinophilic inflammation via triggering of dendritic cells (DCs). Murine Ym1 protein crystals found at sites of eosinophilic inflammation reinforce type 2 immunity and could serve as a surrogate model for studying the biology of human CLCs.

Charcot-Leyden crystals: An ancient but never so current discovery

From the first description of Charcot-Leyden crystals (CLCs) to the present, many steps have been taken to understand the mechanisms underlying their formation. In particular, to date not only eosinophils but also mast cells are known to be responsible for the production of CLCs, which represent the crystallized form of Galectin-10. Due to their characteristics, CLCs typically induce a crystallopathy and are responsible for an exacerbation of inflammation. Nasal cytology (NC) has allowed to better understand the correlation between the severity of several rhinopaties and the presence of CLCs in NC samples, which is strictly correlated with an eosinophiles and mast cells infiltration. As a matter of fact, rhinopaties with a mixed eosinophilic-mast cell inflammatory infiltrate, characterized by the presence of abundant CLCs, show a worse prognosis and a higher risk of relapse. This could have important therapeutic implications, since the treatments available today could be exploited to target both eosinophils and mast cells, to reduce the damage induced by CLCs.

Complete Bone Marrow Necrosis with Charcot-Leyden Crystals Caused by Myeloid Neoplasm with Mutated NPM1 and TET2

Bone marrow necrosis (BMN) has various underlying diseases. In hematological malignancies, both lymphoid and myeloid neoplasms have been shown to cause BMN. Charcot-Leyden crystals (CLCs) are bipyramidal crystals that have been found in patients with immune system diseases, tumors, skin diseases, asthma, infections, and intestinal diseases. Because the combination of CLCs and acute myeloid leukemia (AML) is rare, the relationship between BMN, CLCs, and AML remains largely unexplored. We herein report a suspected case of AML that was difficult to diagnose morphologically because of complete BMN with CLCs but achieved complete hematologic remission with treatment similar to that for AML.

Investigational approaches for unmet need in severe asthma

INTRODUCTION

Molecular antibodies (mAb) targeting inflammatory mediators are effective in T2-high asthma. The recent approval of Tezepelumab presents a novel mAb therapeutic option to those with T2-low asthma.

AREAS COVERED

We discuss a number of clinical problems pertinent to severe asthma which are less responsive to current therapies, such as persistent airflow obstruction and airway hyperresponsiveness. We discuss selected investigational approaches, including a number of candidate therapies under investigation in two adaptive platform trials currently in progress, with particular reference to this unmet need, as well as their potential in phenotypes such as neutrophilic asthma and obese asthma, which may or may not overlap with a T2-high phenotype.

EXPERT OPINION

The application of discrete targeting approaches to T2-low molecular phenotypes, including those phenotypes in which inflammation may not arise within the airway, has yielded variable results to date. Endotypes associated with T2-low asthma are likely to be diverse but await validation. Investigational therapeutic approaches must, likewise, be diverse if the goal of remission is to become attainable for all those living with asthma.

Rethinking neutrophils and eosinophils in chronic rhinosinusitis

Chronic rhinosinusitis (CRS) often is characterized by an eosinophilic inflammatory pattern, nowadays referred to as type 2 inflammation, although the mucosal inflammation is dominated by neutrophils in about a third of the patients. Neutrophils are typically predominant in 50% of patients with CRS without nasal polyps, but also are found to play a role in patients with severe type 2 CRS with nasal polyp disease. This review aims at summarizing the current understanding of the eosinophilic and neutrophilic inflammation in CRS pathophysiology, and provides a discussion of their reciprocal interactions and the clinical impact of the mixed presentation in patients with severe type 2 CRS with nasal polyps. A solid understanding of these interactions is of utmost importance when treating uncontrolled severe CRS with nasal polyps with biologicals that are preferentially directed toward type 2 inflammation. We here focus on recent findings on both eosinophilic and neutrophilic granulocytes, their subgroups and the activation status, and their interactions in CRS.

A substantial neutrophilic inflammation as regular part of severe type 2 chronic rhinosinusitis with nasal polyps

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) is generally associated with severe type 2 immune reactions in the white population. However, recent findings suggest an additional role for neutrophils in severe type 2 inflammation.

OBJECTIVE

This study aimed to characterize the neutrophilic inflammation in CRSwNP and its relation to eosinophilic inflammation in severe type 2 immune reactions.

METHODS

The presence and activation of neutrophils and eosinophils was analyzed in CRS without NP and CRSwNP by measuring cell and activation markers via immunohistochemistry, immunofluorescence, Luminex assay, ELISA, UniCAP, fluorescence-activated cell sorting, and PCR. Differential neutrophil migration was assessed via Boyden-chamber assay and neutrophil survival was analyzed via flow cytometry.

RESULTS

Both CRS without NP and CRSwNP displayed variable degrees of eosinophilic and neutrophilic inflammation, with a profound neutrophilic infiltration and activation in type 2 CRSwNP, associated with eosinophil extracellular traps cell death and Charcot-Leyden crystals, but independent of IL-17. Neutrophil extracellular traps cell death in CRSwNP was associated with bacterial colonization, however, neutrophils were less prone to undergo neutrophil extracellular traps cell death in the tissue of patients with severe type 2 CRSwNP. Neutrophils did not show increased migration nor survival in the CRSwNP environment in vitro.

CONCLUSIONS

This study demonstrated a severe neutrophilic inflammation associated with severe eosinophilic type 2 inflammatory CRSwNP, the role of which needs further study.

The Charcot-Leyden crystal protein revisited-A lysopalmitoylphospholipase and more

The Charcot-Leyden crystal protein (CLC-P), a constituent of human and not mouse eosinophils, is one of the most abundant proteins within human eosinophils. It has a propensity to form crystalline structures, Charcot-Leyden crystals, which are hallmarks in their distinctive extracellular crystalline forms as markers of eosinophilic inflammation. The functions of CLC-P within eosinophils have been uncertain. Although the action of CLC-P as a lysophospholipase has been questioned, assays of chromatographically purified CLC-P and crystal-derived CLC-P as well as studies of transfected recombinant CLC-P have consistently documented that CLC-P endogenously expresses lysophospholipase activity, releasing free palmitate from substrate lysopalmitoylphosphatidylcholine. Rather than acting solely as a hydrolytic enzyme to release palmitate from a lysolipid substrate, some other lysophospholipases function more dominantly as acyl-protein thioesterases (APTs), enzymes that catalyze the removal of thioester-linked, long chain fatty acids, such as palmitate, from cysteine residues of proteins. As such APTs participate in palmitoylation, a post-translational modification that can affect membrane localization, vesicular transport, and secretion. CLC-P has attributes of an APT. Thus, whereas CLC-P expresses inherent lysophospholipase activity, like some other lysophospholipase enzymes, it likely also functions in regulating the dynamic palmitoylation cycle, including, given its dominant subplasmalemmal location, at the human eosinophil's plasma membrane.

Hematochezia before the First Feeding in a Newborn with Food Protein-Induced Enterocolitis Syndrome

The prevalence and incidence of food protein-induced enterocolitis syndrome (FPIES) are clearly not known; its onset before first feeding at birth especially has been rarely reported. A female newborn was referred to our institution due to blood-stained diarrhea before her first feeding at birth. Examination of the stool with Wright-Giemsa staining on day 6 revealed numerous fecal eosinophils, including Charcot-Leyden crystals. Lymphocyte stimulation test (LST) against cow's milk protein also showed positive values on day 12. The hematochezia resolved immediately after starting intravenous nutrition. She was fed with breast milk and extensively hydrolyzed formula and discharged from hospital on day 49. FPIES was diagnosed based on these symptoms and data. Our case was thought to have acquired allergic enterocolitis after sensitization in her fetal period, which caused severe FPIES triggered by the first intake of cow's milk soon after birth. The patient with FPIES presents atypical clinical findings, which is likely to cause misdiagnosis and delay of appropriate treatment. Heightened awareness and increased attention may be necessary to diagnose FPIES, even soon after birth. Evaluating fecal eosinophils and LST, which may be difficult to perform in every clinical hospital, is thought to be useful for the detection of FPIES without oral food challenge.