Expression of the secondary granule proteins major basic protein 1 (MBP-1) and eosinophil peroxidase (EPX) is required for eosinophilopoiesis in mice

Division of Pulmonary Medicine, Department of Biochemistry and Molecular Biology, Mayo Clinic Arizona, Scottsdale, AZ, United States
Blood (Impact Factor: 9.78). 06/2013; 122(5). DOI: 10.1182/blood-2013-01-473405
Source: PubMed

ABSTRACT Eosinophil activities are often linked with allergic diseases such as asthma and the pathologies accompanying helminth infection. These activities have been hypothesized to be mediated, in part, by the release of cationic proteins stored in the secondary granules of these granulocytes. The majority of the protein stored in these secondary granules (by mass) is major basic protein-1 (MBP-1) and eosinophil peroxidase (EPX). Unpredictably, a knockout approach targeting the genes encoding these proteins demonstrated that, unlike mice containing only a single deficiency of either MBP-1 or EPX, the absence of both granule proteins resulted in the near complete loss of peripheral blood eosinophils with no apparent impact on any other hematopoietic lineage. Moreover, the absence of MBP-1 and EPX promoted a concomitant loss of eosinophil lineage committed progenitors (EoP) in the marrow, identifying a specific blockade in eosinophilopoiesis as the causative event. Significantly, this blockade of eosinophilopoiesis is also observed in ex vivo cultures of marrow progenitors and is not rescued in vivo by adoptive bone marrow engraftment, suggesting a cell autonomous defect in marrow progenitors. These observations implicate a role for granule protein gene expression as a regulator of eosinophilopoiesis and provide another strain of mice congenitally-deficient of eosinophils.

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