Interleukin-12 Inhibits Eosinophil Degranulation and Migration but Does Not Promote Eosinophil Apoptosis

Inhaled Kathon may induce eosinophilia-mediated disease in the lung

In 2011, a link between humidifier disinfectants and patients with idiopathic pulmonary fibrosis was identified in Korea, and Kathon was suggested as one of the causative agents. In this study, Kathon induced apoptotic cell death along with membrane damage at 24 h post-exposure. Additionally, on day 14 after a single instillation with Kathon, the total number of pulmonary cells and the levels of TNF-α, IL-5, IL-13, MIP-1α, and MCP-1α clearly increased in the lung of mice. The proportion of natural killer cells and eosinophils were significantly elevated in the spleen and the bloodstream, respectively, and the level of immunoglobulin (Ig) A, but not IgG, IgM, and IgE, dose-dependently increased. Therefore, we suggest that inhaled Kathon may induce eosinophilia-mediated disease in the lung by disrupting homeostasis of pulmonary surfactants. Considering that eosinophilia is closely related to cancer and fibrosis, further studies are needed to understand the relationship between them.

The Innate Immune Cross Talk between NK Cells and Eosinophils Is Regulated by the Interaction of Natural Cytotoxicity Receptors with Eosinophil Surface Ligands

Previous studies suggested that the cross talk between NK cells and other cell types is crucial for the regulation of both innate and adaptive immune responses. In the present study, we analyzed the phenotypic and functional outcome of the interaction between resting or cytokine-activated NK cells and eosinophils derived from non-atopic donors. Our results provide the first evidence that a natural cytotoxicity receptor (NCR)/NCR ligand-dependent cross talk between NK cells and eosinophils may be important to upregulate the activation state and the effector function of cytokine-primed NK cells. This interaction also promotes the NK-mediated editing process of dendritic cells that influence the process of Th1 polarization. In turn, this cross talk also resulted in eosinophil activation and acquisition of the characteristic features of antigen-presenting cells. At higher NK/eosinophil ratios, cytokine-primed NK cells were found to kill eosinophils via NKp46 and NKp30, thus suggesting a potential immunoregulatory role for NK cells in dampening inflammatory responses involving eosinophils.

Eosinophils in human oral squamous carcinoma; role of prostaglandin D2

Eosinophils are often predominant inflammatory leukocytes infiltrating oral squamous carcinoma (OSC) sites. Prostaglandins are secreted by oral carcinomas and may be involved in eosinophil infiltration. The objective of this study was to determine the factors contributing to eosinophil migration and potential anti-neoplastic effects on OSC. Eosinophil degranulation was evaluated by measuring release of eosinophil peroxidase (EPO). Eosinophil chemotaxis towards OSC cells was assessed using artificial basement membrane. Eosinophil infiltration was prominent within the tissue surrounding the OSC tumor mass. We observed growth inhibition of the OSC cell line, SCC-9, during co-culture with human eosinophils, in vitro, which correlated with EPO activity that possesses growth inhibitory activity. The PGD₂ synthase inhibitor, HQL-79, abrogated migration towards SCC-9. Our data suggest that OSC-derived PGD₂ may play an important role via CRTH2 (the PGD₂ receptor on eosinophils) in eosinophil recruitment and subsequent anti-tumor activity through the action of eosinophil cationic proteins.

Eosinophil-mediated tissue inflammatory responses in helminth infection

Eosinophilic leukocytes function in host protection against parasitic worms. In turn, helminthic parasites harbor specific molecules to evade or paralyze eosinophil-associated host immune responses; these molecules facilitate the migration and survival of parasitic helminths in vivo. This competition between eosinophil and worm leads to stable equilibria between them. An understanding of such dynamic host-eosinophil interactions will help us to uncover mechanisms of cross talk between host and parasite in helminth infection. In this review, we examine recent findings regarding the innate immune responses of eosinophils to helminthic parasites, and discuss the implications of these findings in terms of eosinophil-mediated tissue inflammation in helminth infection.

Inhibition of eosinophil migration by lactoferrin

Eosinophilic granulocytes are innate effector cells that are important in immune responses against helminth parasitic infections and contribute towards the pathology associated with allergic inflammatory conditions, including allergic rhinitis and asthma. Their recruitment to inflammatory sites occurs in response to chemotactic and activation signals, such as eotaxin and interleukin-5, and is a tightly controlled process. However, the mechanisms that counterbalance these positive chemoattractive processes, thereby preventing excessive eosinophil infiltration, have received little attention. Here, we show that, lactoferrin (LTF), a pleiotropic 80-kDa glycoprotein with iron-binding properties, acts as a powerful inhibitor of eosinophil migration. Irrespective of its source (milk or neutrophil derived), LTF inhibits eotaxin-stimulated eosinophil migration with no effects on eosinophil viability. Transferrin, a closely related cationic glycoprotein, failed to produce an analogous effect. Furthermore, the iron-saturation status of LTF did not influence the observed inhibitory effect on migration, proving that LTF exerts its effect on eosinophil chemotaxis independent of its iron-chelating activity. These results highlight LTF as one of the few molecules reported to negatively regulate eosinophil migration. Thus, through its ability to inhibit eosinophil migration, LTF has potential as an effective therapeutic in the control of eosinophil infiltration in atopic inflammatory conditions.