Eosinophils in the zebrafish: prospective isolation, characterization, and eosinophilia induction by helminth determinants

Abstract

Eosinophils are granulocytic leukocytes implicated in numerous aspects of immunity and disease. The precise functions of eosinophils, however, remain enigmatic. Alternative models to study eosinophil biology may thus yield novel insights into their function. Eosinophilic cells have been observed in zebrafish but have not been thoroughly characterized. We used a gata2:eGFP transgenic animal to enable prospective isolation and characterization of zebrafish eosinophils, and demonstrate that all gata2 hi cells in adult hematopoietic tissues are eosinophils. Although eosinophils are rare in most organs, they are readily isolated from whole kidney marrow and abundant within the peritoneal cavity. Molecular analyses demonstrate that zebrafish eosinophils express genes important for the activities of mammalian eosinophils. In addition, gata2 hi cells degranulate in response to helminth extract. Chronic exposure to helminthrelated allergens resulted in profound eosinophilia, demonstrating that eosinophil responses to allergens have been conserved over evolution. Importantly, infection of adult zebrafish with Pseudocapillaria tomentosa, a natural nematode pathogen of teleosts, caused marked increases in eosinophil number within the intestine. Together, these observations support a conserved role for eosinophils in the response to helminth antigens or infection and provide a new model to better understand how parasitic worms activate, co-opt, or evade the vertebrate immune response. (Blood. 2010;116(19): 3944-3954) IntroductionEosinophils constitute a distinct lineage of granulocytes that provide innate immune surveillance, assistance with T lymphocytemediated humoral immune responses, and tissue remodeling via release of granule components. 1 In particular, eosinophils have long been thought to act as the primary sentinels against helminth infection. 2 Recent studies in the mouse, however, have demonstrated that sustained helminth infections can require the presence of eosinophils. 3 In addition, further studies in the mouse where eosinophils were specifically ablated using genetic techniques have yielded conflicting phenotypes that differ based on the background strain. 4,5 It has therefore been difficult to determine the precise and specific roles of eosinophils in the immune response. Because most studies of eosinophil function have been performed using the mouse model, we sought an alternative model in which to query eosinophil function.In this report, we identify and characterize eosinophils in the zebrafish, a small cyprinid teleost that features an immune system similar to that of mammals. 6 Critical for their use in immunologic investigation is the fact that both the innate and adaptive immune systems appear to be highly conserved from zebrafish to mammals in terms of gene function, humoral factors, and effector cell lineages. 6 Recent studies have demonstrated that the zebrafish is a suitable host for a variety of infectious diseases, including Grampositive and Gram-negative bacteria, viruses, and parasites. [7][...

The Proprotein Convertase Subtilisin/Kexin FurinA Regulates Zebrafish Host Response against Mycobacterium marinum

“…As in mammals, the cells of the zebrafish immune system include lymphocytes, neutrophils, and macrophages (49), as well as dendritic cells (50), eosinophils (51,52), human mast cell-like cells (53), and natural killer cells (54). Our flow cytometric analyses of furinA td204e/ϩ mutant fish kidneys (the primary site of hematopoiesis in fish) showed normal numbers of lymphocytes, blood cell precursors, and erythrocytes, but low granulocyte counts, indicating that FurinA promotes granulopoiesis.…”

Gata2b is a restricted early regulator of hemogenic endothelium in the zebrafish embryo

“…Erythroid, lymphoid, myeloid and hematopoietic precursor cells within the adult whole kidney marrow (WKM) can be separated by flow cytometry based upon light scatter characteristics . In adult zebrafish, gata2a:GFP is expressed in the kidney marrow, where it primarily labels eosinophils (Balla et al, 2010;Traver et al, 2003). By contrast, gata2b:Gal4 does not drive fluorescence in the adult kidney marrow when combined with either UAS:GFP or UAS: lifeactGFP (Fig.…”

Crystal structures for short-chain pentraxin from zebrafish demonstrate a cyclic trimer with new recognition and effector faces

“…In addition, although CRP and SAP proteins have been characterised in some species of bony fish (Cartwright et al, 2004;Falco et al, 2012;Huong Giang et al, 2010;MacCarthy et al, 2008), the structure of a pentraxin from ectothermic vertebrates has not yet been determined. Recently, zebrafish (Danio rerio) was identified as a vertebrate model for studying evolutionary immunology (Flajnik and Kasahara, 2010), and previous studies have focused on the neutrophil response in zebrafish (Balla et al, 2010;Elks et al, 2011). In the present study, the crystal structures of zebrafish PTX (Dare-PTX) with and without calcium (Dare-PTXCa and Dare-PTX) were determined at 1.65 Å and 1.7 Å resolution, respectively.…”