Bactericidal Activity of Human Eosinophilic Granulocytes againstEscherichia coli

Abstract

Eosinophils participate in allergic inflammation and may have roles in the body's defense against helminthic infestation. Even under noninflammatory conditions, eosinophils are present in the mucosa of the large intestine, where large numbers of gram-negative bacteria reside. Therefore, roles for eosinophils in host defenses against bacterial invasion are possible. In a system for bacterial viable counts, the bactericidal activity of eosinophils and the contribution of different cellular antibacterial systems against Escherichia coli were investigated. Eosinophils showed a rapid and efficient killing of E. coli under aerobic conditions, whereas under anaerobic conditions bacterial killing decreased dramatically. In addition, diphenylene iodonium chloride (DPI), an inhibitor of the NADPH oxidase and thereby of superoxide production, also significantly inhibited bacterial killing. The inhibitor of nitric oxide (NO) production L-N 5 -(1-iminoethyl)-ornithine dihydrochloride did not affect the killing efficiency, suggesting that NO or derivatives thereof are of minor importance under the experimental conditions used. To investigate the involvement of superoxide and eosinophil peroxidase (EPO) in bacterial killing, EPO was blocked by azide. The rate of E. coli killing decreased significantly in the presence of azide, whereas addition of DPI did not further decrease the killing, suggesting that superoxide acts in conjunction with EPO. Bactericidal activity was seen in eosinophil extracts containing granule proteins, indicating that oxygen-independent killing may be of importance as well. The findings suggest that eosinophils can participate in host defense against gram-negative bacterial invasion and that oxygen-dependent killing, i.e., superoxide acting in conjunction with EPO, may be the most important bactericidal effector function of these cells.

Persistence of Mucosal Mast Cells and Eosinophils inShigella-Infected Children

“…This suggests the involvement of other chemokines, such as GM-CSF, in the regulation of eosinophil trafficking to and accumulation in the gastrointestinal tract during recovery from shigellosis (25). The slow protracted release of granule contents by eosinophils and their persistence in the rectum for a prolonged period in children may have a critical role in bactericidal activity (23), induction of antigenspecific T-cell responses (8,33), and wound repair and tissue remodeling by synthesizing transforming growth factor ␤ 1-3 . Mast cells are known to enhance eosinophil survival by releasing TNF-␣ and GM-CSF (11).…”

Experimental Infection of Enterotoxemic Escherichia coli Associated with Porcine Edema Disease and its Pathologic Characteristics in the Intestine

“…Eosinophil infiltration is as well-known a response as is the allergic inflammation in food allergy and asthma, which may contribute to tissue damage and connective tissue remodeling [1,16]. Eosinophils have several properties that contribute to bactericidal activity in tissue, such as cytotoxic protein production and reactive oxygen species production [18]. Accordingly, experimental infection of STEC in weaned piglets triggers local allergic reactions in the small intestine as suggested by the earlier report [17].…”

L’éosinophile : nouvel acteur de la réponse immunitaire innée ?

“…Néanmoins, plusieurs études ont montré que les éosinophiles phagocytent diverses espèces bactériennes comme S. aureus [28], Escherichia coli, et Mycobacterium [29]. Les éosinophiles ont des propriétés bactéricides puisqu'ils participent à la défense de l'hôte contre E. coli, bactérie Gram-, par un mécanisme dépendant de l'oxygène et faisant probablement intervenir l'EPO [30]. Les éosinophiles sont également au coeur d'un équilibre entre la tolé-rance microbienne et l'exacerbation inflammatoire visant à éliminer l'agent microbien et menant à la destruction tissulaire.…”