Galectin-10 is a member of the lectin family and one of the most abundant cytoplasmic proteins in human eosinophils. Except for some myeloid leukemia cells, basophils, and minor T cell populations, galectin-10 is exclusively present in eosinophils in the human body. Galectin-10 forms Charcot–Leyden crystals, which are observed in various eosinophilic diseases. Accumulating studies have indicated that galectin-10 acts as a new biomarker for disease activity, diagnosis, and treatment effectiveness in asthma, eosinophilic esophagitis, rhinitis, sinusitis, atopic dermatitis, and eosinophilic granulomatosis with polyangiitis. The extracellular release of galectin-10 is not mediated through conventional secretory processes (piecemeal degranulation or exocytosis), but rather by extracellular trap cell death (ETosis), which is an active cell death program. Eosinophils undergoing ETosis rapidly disintegrate their plasma membranes to release the majority of galectin-10. Therefore, elevated galectin-10 levels in serum and tissue suggest a high degree of eosinophil ETosis. To date, several studies have shown that galectin-10/Charcot–Leyden crystals are more than just markers for eosinophilic inflammation, but play functional roles in immunity. In this review, we focus on the close relationship between eosinophils and galectin-10, highlighting this protein as a potential new biomarker in eosinophilic diseases.

Objective: Chronic rhinosinusitis with nasal polyps exhibits marked eosinophilic infiltration and its mucosal eosinophilia is associated with more severe symptoms. The Japanese epidemiological survey of refractory eosinophilic chronic rhinosinusitis found that patients with nasal polyps required multiple surgeries when there were higher infiltrating eosinophils in the mucosa. In order to identify plasma biomarkers for local eosinophil infiltration in rhinosinusitis for surgery, we examined the levels of molecules in the plasma of patients and compared the number of infiltrating eosinophils in the nasal mucosa. Materials and Methods: Mucosal tissues from 97 patients with chronic rhinosinusitis (CRS) were obtained from the nasal polyps during surgery. Tissues were immediately fixed and sections were stained with hematoxylin-eosin. The number of eosinophils in the mucosa was counted at HPF (x 400). Blood samples were obtained and the plasma was stored at −80°C. We measured the plasma cytokine and chemokine levels using multiple assay systems according to the manufacturers' protocols. The tissues were divided into high- and low-eosinophil mucosal infiltration group for recurrence after endoscopic sinus surgery (ESS). We also observed chemokine secretion from nasal fibroblasts. Results: The plasma level of eotaxin-3/ CC chemokine ligand 26 (CCL26) was significantly higher in the high-eosinophil mucosal infiltration group (p < 0.005). The number of infiltrating eosinophils in the mucosa was significantly higher in the group with the higher eotaxin-3 level (p < 0.001), but there was no significant difference in the blood eosinophil numbers among two groups. A significant positive correlation was found between the mucosal eosinophil count and the plasma levels of eotaxin-3 (p < 0.005). The levels of interleukin 33 (IL-33) (p < 0.001) and thymic stromal-derived lymphopoietin (TSLP) (p < 0.005) were significantly higher in the high-level eotaxin-3 group. IL-13 strongly induced the secretion of eotaxin-3 from human nasal fibroblasts (p < 0.05). Conclusion: This is the first report suggesting eotaxin-3 as a plasma biomarker for mucosal eosinophil infiltration. Furthermore, the level of eotaxin-3 was found to be closely related to IL-33 and TSLP levels which indicate respiratory diseases.

Adequate treatment is critical for maintaining a good level of quality of life (QOL) during the pollen season in patients suffering from seasonal allergic rhinitis (SAR). Olopatadine, a histamine H₁-receptor antagonist, has been approved in the United States and Europe for the treatment of AR and allergic conjunctivitis as a nasal spray and an ophthalmic solution, respectively. We conducted a randomized, double-blind, placebo-controlled study to determine whether orally administered olopatadine for prophylactic purposes might also be effective for the control of nasal allergy symptoms, especially nasal congestion, in patients with SAR due to Japanese cedar pollen (SAR-JP). A total of 110 patients with SAR caused by JP were randomized to the treatment. The subjects recorded their nasal and ocular allergic symptom scores in a diary, and their QOL was assessed by the Japanese version of the Rhinoconjunctivity Quality of Life Questionnaire. Treatment with oral olopatadine significantly suppressed sneezing (p < 0.001), rhinorrhea (p < 0.001), and nasal congestion (p < 0.05). The total QOL score during the peak JP season was superior in the olopatadine group than in the placebo group (p < 0.05). However, orally administered olopatadine did not exert any significant effect against eye itching and watering of the eyes, unlike olopatadine nasal spray. Treatment with olopatadine tablets yielded superior QOL scores in the domains of usual daily activities and outdoor activities when compared with placebo. No serious adverse effects of the treatment were reported during the study period. These results suggest that oral olopatadine treatment may be a useful alternative treatment strategy for AR.

The "Summary of Japanese clinical practice guidelines for Bell's palsy (idiopathic facial palsy) - 2023 update edited by the Japan Society of Facial Nerve Research" aims to review the latest evidence regarding the treatment of Bell's palsy and to provide appropriate recommendations. Regarding the treatment of Bell's palsy, a guideline panel identified key clinical questions using an analytic PICO framework. The panel produced recommendations following the standards for trustworthy guidelines and the GRADE approach. The panel considered the balance of benefits, harm, and preferences when making recommendations. The panel identified nine key clinical questions: systemic (high/standard dose) corticosteroids, intratympanic corticosteroids, systemic antivirals, decompression surgery, acupuncture, physical therapy, botulinum toxin, and reanimation surgery. These guidelines strongly recommend systemic standard-dose corticosteroids for the clinical management of Bell's palsy. Other treatments are weakly recommended due to insufficient evidence. The absolute risk reduction of each treatment differed according to the disease severity. Therefore, physicians and patients should decide on treatment based on the disease severity.

While group-2 innate lymphoid cells (ILC2s) are highly proliferative in allergic inflammation, the removal of overactivated ILC2s in allergic diseases has not been investigated. We previously showed that chronic airway allergy induces “exhausted-like” dysfunctional ILC2s expressing T cell immunoreceptor with Ig and ITIM domains (TIGIT). However, the physiological relevance of these cells in chronic allergy remains elusive. To precisely identify and monitor TIGIT+ ILC2s, we generated TIGIT lineage tracer mice. Chronic allergy stably induced TIGIT+ ILC2s, which were highly activated, apoptotic, and were quickly removed from sites of chronic allergy. Transcripts from coding genes were globally suppressed in the cells, possibly due to reduced chromatin accessibility. Cell death in TIGIT+ ILC2s was enhanced by interactions with CD155 expressed on macrophages, whereas genetic ablation of Tigit or blockade by anti-TIGIT antagonistic antibodies promoted ILC2 survival, thereby deteriorating chronic allergic inflammation. Our work demonstrates that TIGIT shifts the fate of ILC2s toward activation-induced cell death, which could present a new therapeutic target for chronic allergies.