Innate lymphoid cells (ILCs) have emerged recently as an important component of the immune system and the cell type that regulates mucosal immune responses and tissue homeostasis. Group 2 ILCs (ILC2s), a subset of ILCs, reside in various tissues and are characterized by their capacity to produce type 2 cytokines and tissue growth factors. These ILC2s play an important role in allergic immune responses by linking signals in the atmospheric environment to the immune system. Fungi are one of the major allergens associated with human asthma, and animal and in vitro models using the fungal allergens have provided significant information toward our understanding of the mechanisms of allergic disease. In mouse models of fungus-induced allergic airway inflammation, IL-33, IL-25, and TSLP are released by airway epithelial cells. Lung ILC2s that respond to these cytokines quickly produce a large quantity of type 2 cytokines, resulting in airway eosinophilia, mucus production, and airway hyperreactivity even in the absence of adaptive immune cells. Evidence also suggests that ILC2s interact with conventional immune cells, such as CD4⁺ T cells, and facilitate development of adaptive immune response and persistent airway inflammation. ILC2s are also present in respiratory mucosa in humans. Further investigations into the biology of ILC2s and their roles in the pathophysiology of allergic diseases will provide major conceptual advances in the field and may provide useful information toward development of new therapeutic strategies for patients.

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Group 2 innate lymphoid cells (ILC2s) are recently identified cell populations that produce type 2 cytokines such as IL-5 and IL-13 in response to epithelial cell-derived cytokines. Although ILC2s were initially reported to play a key role in the anti-helminth innate immunity, we now have greater interest in their role in asthma and other allergic diseases. In various asthma mouse models, ILC2s provoke eosinophilic inflammation accompanied by airway hyperresponsiveness independent of acquired immunity. Moreover, recent mouse studies show that ILC2s also promote acquired immunity and Th2 polarization, and various cytokines and lipid mediators influence the functions of ILC2s. Although ILC2s have also been identified in humans, studies on the role of human ILC2s in asthma are very limited. Thus far, human studies have shown that there is a slight difference in responsiveness and production of cytokines between mouse and human ILC2s, and it has been suggested that ILC2s are involved in allergic-type asthma and the exacerbation of asthma. In this review, we focus on mouse and human ILC2s, and discuss their role in asthma.

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Recent advances in our understanding of proallergic cytokines and group 2 innate lymphoid cells (ILC2s) indicate their critical roles in type 2 immunity-mediated disorders. Proallergic cytokines, interleukin (IL)- 25, IL-33, and thymic stromal lymphopoietin, are released from epithelial cells in inflamed tissues and drive type 2 inflammation by acting on innate and acquired immune systems. ILC2s are an innate immune population that responds to proallergic cytokines by producing type 2 cytokines. In line with allergic disorders in the lung, skin, and intestine, emerging evidence suggests the involvement of proallergic cytokines and ILC2s in allergic nasal diseases such as chronic rhinosinusitis with polyps (CRSwNP), allergic fungal rhinosinusitis, and allergic rhinitis (AR). In CRSwNP patients, both proallergic cytokine levels and ILC2s frequency are increased in the nasal mucosa. Increased proallergic cytokine levels correlate with poorer disease outcomes in CRSwNP. Levels of nasal proallergic cytokines are also elevated in AR patients. In addition, animal studies demonstrate that cytokines are essential for the development of AR. It is becoming clear that the proallergic cytokine/ILC2s axis participates in allergic diseases by multiple mechanisms dependent upon the inflammatory context. Thus, a thorough understanding of these cytokines and ILC2s including their tissue- and disease-specific roles is essential for targeting the pathways to achieve therapeutic applications.

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Background: The transcription factors NFATc1 and PU.1 play important roles in osteoclast development. NFATc1 and PU.1 transactivate osteoclast-specific gene expression and a deficiency in NFATc1 or PU.1 genes causes osteopetrosis due to an insufficient development of osteoclasts. However, the existence of cross-regulation between NFATc1 and PU.1 is largely unknown. In the present study, the role of PU.1 in NFATc1 expression was investigated. Methods: Osteoclasts were generated from mouse bone marrow cells. PU.1 knockdown was performed with siRNA introduction. The mRNA levels in siRNA-introduced cells were determined by quantitative RT-PCR. The involvement of PU.1 in the NFATc1 promoter was analyzed by using a chromatin immu- noprecipitation (ChIP) assay and a reporter assay. Retrovirus vector was used for enforced expression of PU.1. Results: Introduction of PU.1 siRNA into bone marrow-derived osteoclasts resulted in a decrease in NFATc1 mRNA level. A ChIP assay showed that PU.1 bound to the NFATc1 promoter in osteoclasts. NFATc1 promoter activity was reduced in PU.1 knockdown cells as assessed by a reporter assay. PU.1 siRNA introduction also downregulated the expression of osteoclast-specific genes and tartrate resistant acid phosphatase (TRAP) activity. Enforced expression of PU.1 using a retrovirus vector increased NFATc1 expression and TRAP activity. When NFATc1 expression was knocked down by using siRNA, the induction of osteoclast-specific genes and TRAP-positive cells was suppressed without affecting the expression level of PU.1. Conclusions: These results indicate that PU.1 is involved in osteoclast development by transactivating NFATc1 expression via direct binding to the NFATc1 promoter.

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Background: Ves v 5 and Pol d 5, which constitute antigen 5, are recognized as the major, most potent allergens of family Vespidae. Several studies have reported the diagnostic sensitivity of the novel re- combinant (r)Ves v 5 and rPol d 5 allergens in routine clinical laboratory settings by analyzing a group of Vespula and Polistes venom-allergic patients. In this study, we analyzed the sensitivity to venom specific (s)IgE by spiking with rVes v 5 and rPol d 5 in Japanese patients suspected of Hymenoptera venom allergy. Methods: Subjects were 41 patients who had experienced systemic reactions to hornet and/or paper wasp stings. Levels of serum sIgE against hornet and paper wasp venom by spiking with rVes v 5 and rPold d 5, respectively, as improvement testing, compared with hornet and paper wasp venom, as conventional testing, were measured by ImmunoCAP. Results: Of the 41 patients, 33 (80.5%) were positive (≥0.35 UA/ml) for hornet and/or paper wasp venom in conventional sIgE testing. sIgE levels correlated significantly (P < 0.01) between hornet (R = 0.92) or paper wasp venom (R = 0.78) in improvement testing and conventional testing. To determine specificity, 20 volunteers who had never experienced a Hymenoptera sting were all negative for sIgE against these venoms in both improvement and conventional testing. Improved sensitivity was seen in 8 patients negative for sIgE against both venoms in conventional testing, while improvement testing revealed sIgE against hornet or paper wasp venom in 5 (total 38 (92.7%)) patients. Conclusions: The measurement of sIgE following spiking of rVes v 5 and rPol d 5 by conventional testing in Japanese subjects with sIgE against hornet and paper wasp venom, respectively, improved the sensitivity for detecting Hymenoptera venom allergy. Improvement testing for measuring sIgE levels against hornet and paper wasp venom has potential for serologically elucidating Hymenoptera allergy in Japan.

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Background: Although there is an increasing number of eosinophilic gastrointestinal disorders (EGID) cases including eosinophilic esophagitis (EoE) and eosinophilic gastroenteritis (EGE), being reported globally, no systematic reviews have been conducted to elucidate the racial differences in these disorders. We aimed to show the racial differences, especially among Caucasians and Asians, in the risk of EoE and EGE. Methods: We conducted a systematic review using PubMed in September 2012. All case reports and case series on EGID that involved human subjects and described race or ethnicity, as well as pathological findings, were included. For the comparison of reported cases between Caucasians and Asians, a chi- squared test was used. Results: Among the 687 studies found in PubMed, 121 studies fulfilled the eligibility criteria. In total, 2621 patients were reviewed. Among Caucasian EGID patients, 94% had EoE; while among Asian EGID patients, 72% had EGE (p < 0.001). Among EoE, Asians were significantly less likely to have dysphagia and heartburn, but more likely to have vomit and abdominal pain, compared to Caucasians (p < 0.001). Further, among EGE, Asians were significantly more likely to have eosinophil-infiltrated colon than Caucasians (OR: 3.22, 95% confidence interval [CI]: 1.60-7.04), but were less likely to have eosinophil-infiltrated stomach (OR: 0.29, 95% CI: 0.17-0.49). Conclusions: We found that EoE occurs more frequently in Caucasian EGID patients than Asian EGID patients, while the reverse is true for EGE. Also, racial disparities in symptoms and eosinophil-infiltrated tissues were observed. Our findings suggest further genetic and environmental studies to elucidate the etiology of EGID.

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Background: The prevalence rate of eosinophilic esophagitis (EoE) between Japan and Western countries is quite different. Although multiple factors, including the genetic background, lifestyle and dietary habits, may account for the difference, the pathogenic mechanism of EoE has not been fully clarified in Japanese. To elucidate whether EoE's pathogenic mechanisms differ between those populations, we performed transcriptome analysis of esophageal biopsy specimens from Japanese EoE patients and compared the identified gene signatures with published microarray data for EoE patients in the US. Methods: We prospectively enrolled adult Japanese EoE patients (n = 4) according to the 2011 consensus guidelines for diagnosis of EoE. Age-matched healthy volunteer subjects (n = 4) were also enrolled as controls. We assessed the gene expression profiles of esophageal biopsies using microarray technology and then compared the identified gene signatures with earlier data generated in the US. Results: Of 42,545 transcripts represented on the microarray, 385 were differentially expressed between the EoE and control samples (≥2 fold change and adjusted p-value of < 0.05). Our microarray data showed strong overlapping with the data from US patients with EoE. An EoE-specific-transcript signature is typically composed of IL-13-inducible and eosinophil-related genes, including eotaxin-3/C-C chemokine ligand 26 (CCL26). Conclusions: This transcriptome study suggests that the pathogenetic mechanisms of EoE in Japan and Western countries are similar. Our findings may contribute to a better understanding of the pathogenesis of EoE and to more accurate diagnosis of this disease in Japanese individuals.

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Background: We previously identified MGL_1304 secreted by Malassezia globosa as a sweat antigen for patients with atopic dermatitis (AD) and cholinergic urticaria (ChU). However, purifying native MGL_1304 from human sweat or culture supernatant of M. globosa (sup-MGL_1304) is costly and time- consuming. Moreover, recombinant MGL_1304 expressed by using Escherichia coli (TF-rMGL_1304) needs a large chaperon protein and lacks the original glycosylation of yeasts. Thus, we generated a recombinant MGL_1304 by Pichia pastoris (P-rMGL_1304) and investigated its characteristic features. Methods: Recombinant MGL_1304 proteins expressed by E. coli and P. pastoris were generated. Properties of these recombinants and native antigens were compared by western blot analysis, histamine release tests (HRT) of patients with AD and ChU, and β-hexosaminidase release tests with RBL-48 cells. P- rMGL_1304-specific IgE in sera of patients with AD were measured by sandwich ELISA. Results: Western blot analysis revealed that IgE of patients with AD bound to all MGL_1304 recombi- nants and native antigens. The histamine releasing ability of P-rMGL_1304 was 100 times higher than that of TF-rMGL_1304, and was comparable to that of sup-MGL_1304. Degranulation rates of RBL-48 cells, sensitized with sera of patients with AD in response to the stimulation of P-rMGL_1304, were comparable to those of sup-MGL_1304, whereas those of TF-rMGL_1304 were relatively weak. The levels of P-rMGL_1304-specific IgE in sera of patients with AD were correlated with their disease severities. Conclusions: P-rMGL_1304 has an antigenicity comparable to the native antigen, and is more useful than TF-rMGL_1304, especially in HRT and degranulation assay of RBL-48 cells.

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Background: Low dose reactive cow's milk (CM) allergic children are at high risk of persistent CM allergy and a positive oral food challenge (OFC). The present study aimed to evaluate if the results of a very low dose (VL) OFC with these children contributes to better management of CM allergy. Methods: We retrospectively reviewed subjects with CM allergy who underwent a VL OFC with 3 mL heated CM and had a previous allergic reaction to < 25 mL heated CM in the 2 years before the OFC. Subjects who passed the OFC were defined as VL tolerant, and subjects who failed were defined as VL reactive. VL tolerant subjects increased the dose to 25 mL heated CM either during an OFC in our hospital or gradually at home. Results: Of the 83 subjects (median age, 4.3 years; range, 1.0-12.9 years) who were included, 41 (49.4%) were VL tolerant, and 42 (51.6%) were VL reactive. Thirty-nine VL reactive subjects had skin and/or respiratory symptoms during the OFC. Most reactions could be treated with an antihistamine and/or a nebulized β2 agonist. The VL tolerant subjects consumed 3 mL heated CM or 10 g butter. Within the year following the OFC, 18 VL tolerant subjects (45.0%), but none of the VL reactive subjects, were able to consume 25 mL heated CM (p < 0.001). Conclusions: A VL OFC allows the management of some low dose reactive CM allergic children to change from complete avoidance to partial intake of CM.

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