Dual function of eosinophils in pathogenesis and protective immunity against parasites

Abstract

The functional duality of eosinophils, involved in a protective response or in pathogenesis is illustrated in various parasitic infections. In schistosomiasis, eosinophils have been shown to mediate schistosomula killing, in the presence of antibodies. The association of eosinophil-dependent cytotoxic antibody isotypes with resistance of reinfection (IgE and IgA antibodies), whereas in vitro blocking antibody isotypes (IgG4, IgM) were detected in susceptible subjects, suggested a participation of eosinophils in antibody-dependent protective response. However eosinophils could participate to granuloma formation and consequently to the pathological reactions during schistosomiasis. Activation of eosinophils by antibodies, leading to release of granule proteins have been studied in patients with filariasis. Eosinophil peroxidase, EPO was released after IgE-dependent activation whereas Eosinophil Cationic Protein, ECP, was released after IgG- and IgA-dependent activation of eosinophils, results suggesting a process of differential release of mediators. Interactions between eosinophils and interleukins, and specially IL-5 are discussed. Whereas a receptor for IL-5 has been characterized on human eosinophils, recent studies have shown that eosinophils expressed the messenger RNA encoding IL-5. These results associated to data showing the synthesis of other cytokines indicate that eosinophils are not only the source of cytotoxic mediators involved in the effector phase of immunity but also of growth and regulatory factors, participating to immunoregulation.

Interleukin-5 (IL-5) Augments the Progression of Liver Fibrosis by Regulating IL-13 Activity

“…Although the role of IL-5 in granuloma formation was investigated previously, the contribution of IL-5 and eosinophils to the progression of hepatic fibrosis in chronically infected mice was not examined (1,3,12,28,31). The specific role of granuloma-associated eosinophils was also unexplored in those studies.…”

High expression of co-stimulatory and adhesion molecules are observed on eosinophils during human Schistosoma mansoni infection

“…5) focusing on the expression of CD62L by eosinophils from INT patients using tertile, showed that the unusual relationship between the expression of L-selectin and most cell activation related markers was maintained in individuals in the first tertile, whereas those patients in the second CD62L tertile shared the CD62L expression profile with that of non-infected individuals. the chronic infection, the eosinophils may play important role in the innate immune response of chronic infected patients as they represent a relevant protective antischistosomula mechanism (Capron & Capron 1992, Capron 1992. Moreover, the numbers of eosinophils increase following re-infections its relevance during S. mansoni infection should be considered.…”

Extensive Eosinophil Degranulation and Peroxidase-Mediated Oxidation of Airway Proteins Do Not Occur in a Mouse Ovalbumin-Challenge Model of Pulmonary Inflammation

“…RNA samples were treated with RNase-free DNase I (RQ1; Promega, Madison, WI) for 30 min at 37°C, followed by phenol/chloroform extraction and ethanol precipitation before reverse transcription reactions. Total RNA (1 g) was reverse transcribed with SuperScript II reverse transcriptase (Life Technologies, Rockville, MD) in the presence of anchored oligo(dT) primers (dT 16 VN where V ϭ A, C, or G and N ϭ A, C, G, or T) according to the manufacturer's instructions. PCRs were performed using cDNA derived from one-tenth of the reverse transcriptase reactions (i.e., cDNA derived from 100 ng total RNA) in 50-l reactions with 1 M of EPO-specific primers and 5 U Taq polymerase (Boehringer Mannheim, Indianapolis, IN).…”

“…This selective recruitment suggested that pulmonary pathologies arise, in part, as a consequence of eosinophil effector functions. Indeed, studies have implicated eosinophils as immunoregulative cells modulating the inflammatory response (15,16) as well as proinflammatory cells whose activities lead to epithelial desquamation, airway smooth muscle perturbation, and tissue remodeling (17).…”