Eosinophils: Nemeses of Pulmonary Pathogens?
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Purpose of Review
Eosinophils are short-lived granulocytes that contain a variety of proteins and lipids traditionally associated with host defense against parasites. The primary goal of this review is to examine more recent evidence that challenged this rather outdated role of eosinophils in the context of pulmonary infections with helminths, viruses, and bacteria.
While eosinophil mechanisms that counter parasites, viruses, and bacteria are similar, the kinetics and impact may differ by pathogen type. Major antiparasitic responses include direct killing and immunoregulation, as well as some mechanisms by which parasite survival/growth is supported. Antiviral defenses may be as unembellished as granule protein-induced direct killing or more urbane as serving as a conduit for better adaptive immune responses to the invading virus. Although sacrificial, eosinophil DNA emitted in response to bacteria helps trap bacteria to limit dissemination. Herein, we discuss the current research redefining eosinophils as multifunctional cells that are active participants in host defense against lung pathogens.
Eosinophils recognize and differentially respond to invading pathogens, allowing them to deploy innate defense mechanisms to contain and clear the infection, or modulate the immune response. Modern technology and animal models have unraveled hitherto unknown capabilities of this surreptitious cell that indubitably has more functions awaiting discovery.
KeywordsHelminth Virus Bacteria
AES wishes to thank all those eosinophil aficionados (Drs. Helene Rosenberg, Praveen Akuthota, Rossana Melo, Hirohito Kita, Elizabeth Jacobsen, and especially the late Dr. James Lee) that have guided her viewpoint through conversation on all “things” eosinophil! We thank John Snyder for the artistic rendering of the eosinophil.
This work was supported in part by the National Institutes of Allergy and Infectious Diseases of the National Institutes of Health under award number R01AI125481 to AES.
Compliance with Ethical Standards
The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Conflict of Interest
The authors declare no conflicts of interest relevant to this manuscript.
Human and Animal Rights and Informed Consent
This article does not contain any studies with human or animal subjects performed by any of the authors.
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