Citations

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.

Abstract The Human Phenotype Ontology (HPO) is a widely used resource that comprehensively organizes and defines the phenotypic features of human disease, enabling computational inference and supporting genomic and phenotypic analyses through semantic similarity and machine learning algorithms. The HPO has widespread applications in clinical diagnostics and translational research, including genomic diagnostics, gene-disease discovery, and cohort analytics. In recent years, groups around the world have developed translations of the HPO from English to other languages, and the HPO browser has been internationalized, allowing users to view HPO term labels and in many cases synonyms and definitions in ten languages in addition to English. Since our last report, a total of 2239 new HPO terms and 49235 new HPO annotations were developed, many in collaboration with external groups in the fields of psychiatry, arthrogryposis, immunology and cardiology. The Medical Action Ontology (MAxO) is a new effort to model treatments and other measures taken for clinical management. Finally, the HPO consortium is contributing to efforts to integrate the HPO and the GA4GH Phenopacket Schema into electronic health records (EHRs) with the goal of more standardized and computable integration of rare disease data in EHRs.

Abstract Extracellular ATP (eATP) is a danger signal released by inflamed tissues, and can be sensed by immune cells via P2RX7. P2RX7 promotes lung pathology induced by influenza infection, by inducing exacerbated numbers of lung CD4+ T cells. In response to influenza, lung CD4+ T cells are comprised of a type 1 (Th1)-like population, and a subset resembling follicular helper (Tfh) CD4+ T cells; this subset is called tissue-resident helper (Trh). Trh cells amplify lung effector immune responses. Trh cells express high P2RX7 levels, and current research in our laboratory shows that P2RX7 is crucial for Trh cell establishment and subsequent lung damage. We have also found that the intensity of lung damage caused by influenza is positively correlated with P2RX7+ lung Trh cells. It is not clear, however, how concomitant exposure to influenza and type 2 immunity-inducing lung allergens (a common clinical occurrence in the United States) affect P2RX7+ lung Trh cells and their resultant tissue damage. We investigated this, using House Dust Mite (HDM) allergen exposure together with Influenza (PR8) infection. HDM/PR8 co-exposure induced worsening of lung inflammation, compared to single exposure to PR8. This inflammation had type 1 characteristics (i.e. parenchymal immune cell accumulation and absence of mucus). The increased lung damage generated by HDM/PR8 exacerbated the generation of influenza-specific P2RX7+ lung Trh cells. The accumulation of lung Trh cells (and subsequent tissue damage) caused by HDM/PR8 was abolished in T cell-specific P2RX7-knockout mice. Our results suggest that local inflammation, eATP release and sensing, and lung Trh cells together dictate the intensity of lung damage, regardless of the nature of the lung disease agent. R01AI170649

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

Abstract Eosinophils play a surprising role in downregulating lung graft-specific alloimmunity, even without immunosuppression. We demonstrate here, a mechanism used by eosinophils to downregulate alloimmune responses. To study the mechanism of eosinophil dependent downregulation of alloimmune responses, we used a model of diphtheria toxin (DT) dependent ablation of eosinophils in iPHIL, a mouse model expressing DT receptor on the eosinophil-peroxidase gene locus. Fully MHC-mismatched Balb/c (H2Kd) lungs were engrafted to iPHIL (H2Kb) recipients without immunosuppression. We modeled alloreactivity in vitro, with mixed leukocyte cultures, comprising Th1-polarized eosinophils as modulators of T cells from C57BL/6J or Nur77-GFP mice stimulated by either allogeneic dendritic cells or anti-CD3/CD28 agonistic antibodies. Ablation of eosinophils in non-immunosuppressed lung graft recipients leads to enhanced T cell activation and graft rejection. Similarly, in vitro, we observed a dose and contact dependent downregulation of T cell activation by eosinophils. While contact between eosinophils and T cells is mediated through the upregulation of PD-L1 on both wild-type and iNOS−/− eosinophils after TH-1 polarization, the inhibition of T cell activation is iNOS dependent and is directly linked to the iNOS dependent inhibition of the TCR signaling early gene, Nr4a1, monitored in Nur77-GFP mice. Thus, following contact with T cells, iNOS-expressing eosinophils downregulate lung graft alloimmunity through a direct effect on TCR engagement early genes, leading to the inhibition of T cell activation. This provides an explanation for the surprising observation of lung-graft specific alloimmune downregulation by eosinophils.

Abstract Chronic asthma is characterized by pulmonary remodeling and sustained lung dysfunction. The expression of IL-13 has been demonstrated as sufficient and necessary to induce these pathologies. Despite the common assumption that T cells are the primary source of IL-13 in the lung following allergen provocation, the mechanistic events leading to IL-13 expression are unclear, including the potential importance of other cells (i.e., non-T cells). Methods: Co-expression of IL-5 and eotaxin-2 induces pulmonary histopathologies and lung dysfunction that are eosinophil-dependent (i.e., they are absent in triple transgenic I5/hE2/PHIL) animals. IL-13 knockout and CD4 knockout mice were crossed with I5/hE2 mice to assess the effects of these deficiencies on the induced pathologies occurring in this double transgenic model. Conclusions: The Th2 pulmonary pathologies associated with I5/hE2 mice included recruitment of pulmonary effector T cells and increased brochoalveolar Th2 cytokine levels. Conversely, I5/hE2/CD4-/- had only a ~50% reduction in IL-13 levels as compared to I5/hE2 mice, suggesting that a significant portion of IL-13 is non-T cell derived in these mice. I5/hE2/IL-13-/- mice are improved in lung dysfunction and mucus production as compared to I5/hE2 mice. All mice had similar levels of eosinophil degranulation. These results demonstrate a role for non-T cell derived IL-13 that contributes to mucus production and lung dysfunction in a mouse model of chronic severe asthma.

Abstract Eosinophil infiltration into tumors has been associated with positive and negative growth human cancers and in mouse models of tumorigenesis. Our previous studies have shown that eosinophils infiltrate tumors and differentially accumulate in the necrotic and capsule regions of tumors. Using various eosinophil-deficient mouse models, we demonstrate that in the absence of eosinophils tumor growth is attenuated. Methods: Tumor growth kinetics were assessed using a B16F10 melanoma subcutaneous cell injection model. Eosinophil chemotaxis was assessed using an ex vivo transwell insert assay system. We compared tumor growth in wild type animals vs. various eosinophil-deficient mouse models that are transgenic line of mice (PHIL) and MBP-/-/EPO-/- double knockout mice that are deficient in eosinophil-specific proteins (major basic protein (MBP) and eosinophil peroxide (EPO)) resulting in a blockade of eosinophilpoiesis. Conclusions: The migration of eosinophils was inhibited through blocking the sphingosine-1-phosphate pathway, suggesting recruitment and accumulation is primarily an inflammatory response. Tumor growth was decreased by ~40-60% in PHIL and in MBP-/-/EPO-/- double knockout mice relative to tumors in wild type animals. In addition, EPO-/- mice, and not MBP-/-mice, replicate this ~40% reduction in tumor size implicating a significant role for EPO in tumor growth kinetics. These data suggest eosinophils respond to inflammatory mediators and mediate augment tumor growth.