Jacobsen, Elizabeth A

Inflammatory bowel disease (IBD) is driven by a breakdown in immune regulation and epithelial barrier function, yet the contribution of eosinophils to this process has remained poorly defined and controversial. While eosinophils infiltrate the intestinal mucosa during both flares and remission, their role in shaping disease outcomes is unclear. Our RNA-seq analyses of colonic eosinophils isolated from dextran sulfate sodium (DSS)-treated mice revealed a significant upregulation of cyclooxygenase (COX)-2 (gene name, Ptgs2 ). Eosinophil-specific deletion of COX-2 (Ptgs2 fl/fl eoCre +/− ) reduced IL-22 production and exacerbated DSS- and trinitrobenzene sulfonic acid (TNBS)-induced colitis, characterized by greater weight loss, higher disease activity, colon shortening, and epithelial injury. Administration of recombinant IL-22 reversed these phenotypes. Mechanistically, eosinophil-derived COX-2 enhanced IL-22 production by type 3 Innate lymphoid cells (ILC3s) through prostaglandin E2 (PGE 2 ) signaling. Consistently, Ptgs2 fl/fl eoCre +/− mice exhibited reduced colonic PGE 2 levels, while PGE 2 analog treatment restored IL-22 production and mucosal protection. Our findings identify eosinophil-derived COX-2 and PGE 2 as a critical regulator of IL-22 production during colitis, uncovering a eosinophil–ILC3 cross talk that safeguards the intestinal barrier and represents a promising therapeutic target in IBD.

Technological innovations have improved many barriers in lung transplantation, but high rates of acute and chronic rejection still limit lung allograft survival. This may be explained by the unique environment of the lung. As a mucosal barrier organ, the lung is constantly exposed to the external environment, leading to unique immunological features that are not seen in other transplantable solid organ allografts such as hearts, kidneys, and livers. Thus, the higher rates of rejection and poor long-term survival of lung transplant recipients may stem from the global immunosuppression strategies that are indiscriminately used for all solid organ grafts. Data from our laboratory, and others, have demonstrated that the unique immunoregulatory pathways of the lung may require different strategies for long-term graft survival. For example, depletion of CD8 + T cells typically contributes to the acceptance of transplanted organs. However, these cells facilitate lung allograft acceptance through interferon gamma mediated nitric oxide production. Interestingly CD8 + T cells modify and polarize eosinophils to produce nitric oxide as a means of tolerance induction. Such eosinophils also function to maintain long-term lung allograft acceptance by interfering with humoral alloimmunity. For most other organs eosinophils are suspected to contribute to graft rejection. In this review, we aim to describe the cytokine pathways involved in lung allograft rejection or tolerance, contrast such pathways to those evident in other solid organs, and discuss the need for further studies that can be used to design rational methods for altering the cytokine environment to improve lung allograft survival.

Abstract Food allergy can be life threatening and often develops early in life, especially in infants and children with atopic dermatitis. Food allergy is induced in neonatal mice with skin barrier mutations (Flaky Tail, FT+/− mice with filaggrin and mattrin gene mutations) by epicutaneous sensitization with co-exposures to the food allergen peanut extract (PNE), the environmental allergen Alternaria alternata (Alt), and detergent (4% SDS); oral PNE-challenge induces anaphylaxis. Sensitization in these neonates also induces eosinophil infiltration into the skin and elevates skin expression of eotaxins (CCL11 and CCL24). However, roles for eosinophils in food allergy are not known. In this study, the iPhil+/− FT+/− pups, which have an inducible eosinophil-deficiency upon injection of diphtheria toxin (DTX), were sensitized and then received PNE by gavage to assess anaphylaxis. DTX depletion of eosinophils, during sensitization and oral PNE-challenge, blocked the recruitment and activation of mast cells, blocked the Alt+PNE-induced increase in plasma IL-33 and OSM, attenuated serum PNE-specific IgE/IgG1/IgG2b, and blocked oral-PNE-induced anaphylaxis. Anti-IL-5 depletion of eosinophils during sensitization/challenge also blocked anaphylaxis. When eosinophils were depleted during allergen-skin-sensitization and restored before oral PNE-challenge, anaphylaxis was blocked. In contrast, when eosinophils were present during allergen-skin-sensitization but then depleted during oral PNE-challenge, anaphylaxis was not blocked. Together, these data indicate that although eosinophils are not necessary during oral food allergen-induced anaphylaxis, eosinophils have a critical role during the development of food allergy early in life by regulating the sensitization-induced increase in mast cell numbers and food allergen-specific IgE.

Respiratory failure occurs more frequently after thoracic surgery than abdominal surgery. Although the etiology for this complication is frequently attributed to underlying lung disease present in patients undergoing thoracic surgery, this notion is often unfounded because many patients with normal preoperative pulmonary function often require prolonged oxygen supplementation even after minimal resection of lung tissue. Using a murine model of pulmonary resection and peripheral blood samples from patients undergoing resection of the lung or abdominal organs, we demonstrated that lung surgery initiates a proinflammatory loop that results in damage to the remaining lung tissue, noncardiogenic pulmonary edema, hypoxia, and even death. Specifically, we demonstrated that resection of murine lung tissue increased concentrations of the homeostatic cytokine interleukin-7, which led to local and systemic activation of type 2 innate lymphoid cells. This process activated lung-resident eosinophils and facilitated stress-induced eosinophil maturation in the bone marrow in a granulocyte-macrophage colony-stimulating factor–dependent manner, resulting in systemic eosinophilia in both mice and humans. Up-regulation of inducible nitric oxide synthase in lung-resident eosinophils led to tissue nitrosylation, pulmonary edema, hypoxia, and, at times, death. Disrupting this activation cascade at any stage ameliorated deleterious outcomes and improved survival after lung resection in the mouse model. Our data suggest that repurposing US Food and Drug Administration–approved eosinophil-targeting strategies may potentially offer a therapeutic intervention to improve outcomes for patients who require lung resection for benign or malignant etiology.

Objective Previous studies indicate that eosinophils are recruited into the allograft following orthotopic liver transplantation and protect from ischaemia reperfusion (IR) injury. In the current studies, we aim to explore whether their protective function could outlast during liver repair. Design Eosinophil-deficient mice and adoptive transfer of bone marrow-derived eosinophils (bmEos) were employed to investigate the effects of eosinophils on tissue repair and regeneration after hepatic IR injury. Aside from exogenous cytokine or neutralising antibody treatments, mechanistic studies made use of a panel of mouse models of eosinophil-specific IL-4/IL-13-deletion, cell-specific IL-4rα-deletion in liver macrophages and hepatocytes and macrophage-specific deletion of heparin-binding epidermal growth factor-like growth factor (hb-egf). Result We observed that eosinophils persisted over a week following hepatic IR injury. Their peak accumulation coincided with that of hepatocyte proliferation. Functional studies showed that eosinophil deficiency was associated with a dramatic delay in liver repair, which was normalised by the adoptive transfer of bmEos. Mechanistic studies demonstrated that eosinophil-derived IL-4, but not IL-13, was critically involved in the reparative function of these cells. The data further revealed a selective role of macrophage-dependent IL-4 signalling in liver regeneration. Eosinophil-derived IL-4 stimulated macrophages to produce HB-EGF. Moreover, macrophage-specific hb-egf deletion impaired hepatocyte regeneration after IR injury. Conclusion Together, these studies uncovered an indispensable role of eosinophils in liver repair after acute injury and identified a novel crosstalk between eosinophils and macrophages through the IL-4/HB-EGF axis.

BACKGROUND Obesity is a multifactorial disease with adverse health implications including insulin resistance (IR). In patients with obesity, the presence of high circulating levels of leptin, deemed hyperleptinemia, is associated with IR. Recent data in mice with diet-induced obesity (DIO) show that a partial reduction in leptin levels improves IR. Additional animal studies demonstrate that IL-4 decreases leptin levels. In rodents, resident adipose tissue eosinophils (AT-EOS) are the main source of IL-4 and are instrumental in maintaining metabolic homeostasis. A marked reduction in AT-EOS content is observed in animal models of DIO. These observations have not been explored in humans. METHODS We analyzed AT from individuals with obesity and age-matched lean counterparts for AT-EOS content, IL-4, circulating leptin levels, and measures of IR. RESULTS Our results show that individuals with obesity ( n = 15) had a significant reduction in AT-EOS content ( P < 0.01), decreased AT–IL-4 gene expression ( P = 0.02), and decreased IL-4 plasma levels ( P < 0.05) in addition to expected IR ( P < 0.001) and hyperleptinemia ( P < 0.01) compared with lean subjects ( n = 15). AT-EOS content inversely correlated with BMI ( P = 0.002) and IR ( P = 0.005). Ex vivo AT explants and in vitro cell culture of primary human mature adipocytes exposed to either IL-4 or EOS conditioned media produced less leptin ( P < 0.05). CONCLUSION Our results suggest that IL-4 acts as a link between EOS, AT, and leptin production. Future studies exploring this interaction may identify an avenue for the treatment of obesity and its complications through amelioration of hyperleptinemia. TRIAL REGISTRATION Clinicaltrials.gov NCT02378077 & NCT04234295.

While the function of many leukocytes in transplant biology has been well defined, the role of eosinophils is controversial and remains poorly explored. Conflicting data exist regarding eosinophils’ role in alloimmunity. Due to their prevalence in the lung, and their defined role in other pulmonary pathologies such as asthma, we set out to explore the role of eosinophils in the long-term maintenance of the lung allograft. We noted that depletion of eosinophils results in the generation of donor-specific antibodies. Eosinophil depletion increased memory B cell, plasma cell, and antibody-secreting cell differentiation and resulted in de novo generation of follicular germinal centers. Germinal center formation depended on the expansion of CD4 + Foxp3 – Bcl6 + CXCR5 + PD-1 + T follicular helper (Tfh) cells, which increase in number after eosinophil depletion. Mechanistically, we demonstrate that eosinophils prevent Tfh cell generation by acting as the dominant source of IFN-γ in an established lung allograft, thus facilitating Th1 rather than Tfh polarization of naive CD4 + T cells. Our data thus describe what we believe is a unique and previously unknown role for eosinophils in maintaining allograft tolerance and suggest that indiscriminate administration of eosinophil-lytic corticosteroids for treatment of acute cellular rejection may inadvertently promote humoral alloimmunity.

Staphylococcus aureus skin colonization and eosinophil infiltration are associated with many inflammatory skin disorders, including atopic dermatitis, bullous pemphigoid, Netherton’s syndrome, and prurigo nodularis. However, whether there is a relationship between S. aureus and eosinophils and how this interaction influences skin inflammation is largely undefined. We show in a preclinical mouse model that S. aureus epicutaneous exposure induced eosinophil-recruiting chemokines and eosinophil infiltration into the skin. Remarkably, we found that eosinophils had a comparable contribution to the skin inflammation as T cells, in a manner dependent on eosinophil-derived IL-17A and IL-17F production. Importantly, IL-36R signaling induced CCL7-mediated eosinophil recruitment to the inflamed skin. Last, S. aureus proteases induced IL-36α expression in keratinocytes, which promoted infiltration of IL-17-producing eosinophils. Collectively, we uncovered a mechanism for S. aureus proteases to trigger eosinophil-mediated skin inflammation, which has implications in the pathogenesis of inflammatory skin diseases.

Objective To evaluate eosinophil peroxidase (EPX) as a biomarker for tissue levels of eosinophilia, cytokines, and chemokines within chronic rhinosinusitis (CRS). Methods Twenty‐eight subjects undergoing sinonasal surgery were prospectively enrolled. Ethmoid tissue was analyzed with an in‐house EPX immunoassay and a 48‐plex cytokine‐chemokine array. Clinical severity was assessed using SNOT‐22 and Lund‐Mackay scores. Subjects were grouped as follows: controls, polyp status (CRS with [CRSwNP] and without nasal polyps [CRSsNP]), tissue eosinophilia (eosinophilic CRS [eCRS], non‐eosinophilic CRS [neCRS]), or combinations thereof (eCRSwNP, eCRSsNP, neCRSsNP). eCRS was defined as >10 eosinophils per high power field (HPF). Subjects without CRS or asthma were enrolled as controls. Results EPX was elevated in CRSwNP compared to control ( p = 0.007), in eCRS compared to neCRS ( p = 0.002), and in eCRSwNP along with eCRSsNP compared to neCRSsNP ( p = 0.023, p = 0.015, respectively). eCRS displayed elevated IL‐5 compared to neCRS ( p = 0.005). No significant differences in EPX or IL‐5 were observed between eCRSwNP and eCRSsNP. IL‐5 was elevated in eCRSwNP ( p = 0.019) compared neCRSsNP. Area under the receiver operator characteristic curve was 0.938 (95% CI, 0.835–1.00) for EPX and tissue eosinophilia, with an optimal cut‐point of 470 ng/mL being 100% specific and 81.25% sensitive for tissue eosinophilia. Linear regression revealed a strong correlation between EPX and IL‐5 (R 2 = 0.64, p < 0.001). Comparing EPX and IL‐5, only EPX displayed significant correlation with SNOT‐22 ( p = 0.04) and Lund‐Mackay score ( p = 0.004). Conclusion EPX is associated with tissue eosinophilia in CRS patients regardless of polyp status. EPX correlates with IL‐5 and could be potentially considered a biomarker for anti‐IL‐5 therapies. Level of Evidence 3 Laryngoscope , 134:69–78, 2024

Background and Aims: A better understanding of the underlying mechanism of acetaminophen (APAP)‐induced liver injury (AILI) remains an important endeavor to develop therapeutic approaches. Eosinophils have been detected in liver biopsies of patients with APAP overdose. We recently demonstrated a profound protective role of eosinophils against AILI; however, the molecular mechanism had not been elucidated. Approach and Results: In agreement with our previous data from experiments using genetic deletion of eosinophils, we found that depletion of eosinophils in wild‐type (WT) mice by an anti‐IL‐15 antibody resulted in exacerbated AILI. Moreover, adoptive transfer of eosinophils significantly reduced liver injury and mortality rate in WT mice. Mechanistic studies using eosinophil‐specific IL‐4/IL‐13 knockout mice demonstrated that these cytokines, through inhibiting interferon‐γ, mediated the hepatoprotective function of eosinophils. Reverse phase protein array analyses and in vitro experiments using various inhibitors demonstrated that IL‐33 stimulation of eosinophils activated p38 mitogen‐activated protein kinase (MAPK), and in turn, cyclooxygenases (COX), which triggered NF‐κB–mediated IL‐4/IL‐13 production. In vivo adoptive transfer experiments showed that in contrast to naive eosinophils, those pretreated with COX inhibitors failed to attenuate AILI. Conclusions: The current study revealed that eosinophil‐derived IL‐4/IL‐13 accounted for the hepatoprotective effect of eosinophils during AILI. The data demonstrated that the p38 MAPK/COX/NF‐κB signaling cascade played a critical role in inducing IL‐4/IL‐13 production by eosinophils in response to IL‐33.