Abstract

BACKGROUND: The innate immune response constitutes the first line of defense against invading pathogens and consists of a variety of immune defense mechanisms including active endocytosis by macrophages and granulocytes. Endocytosis can be used as a reliable measure of selective and non-selective mechanisms of antigen uptake in the early phase of an immune response. Numerous assays have been developed to measure this response in a variety of mammalian and fish species. The small size of the zebrafish has prevented the large-scale collection of monocytes/macrophages and granulocytes for these endocytic assays. METHODOLOGY/PRINCIPAL FINDINGS: Pooled zebrafish kidney hematopoietic tissues were used as a source of phagocytic cells for flow-cytometry based endocytic assays. FITC-Dextran, Lucifer Yellow and FITC-Edwardsiella ictaluri were used to evaluate selective and non-selective mechanisms of uptake in zebrafish phagocytes. CONCLUSIONS/SIGNIFICANCE: Zebrafish kidney phagocytes characterized as monocytes/macrophages, neutrophils and lymphocytes utilize macropinocytosis and Ca(2+)-dependant endocytosis mechanisms of antigen uptake. These cells do not appear to utilize a mannose receptor. Heat-killed Edwardsiella ictaluri induces cytoskeletal interactions for internalization in zebrafish kidney monocytes/macrophages and granulocytes. The proposed method is easy to implement and should prove especially useful in immunological, toxicological and epidemiological research.

Publisher

Public Library of Science

DOI

10.1371/journal.pone.0004314

Publication Date

2-2-2009

College

College of Veterinary Medicine

Department

Department of Basic Sciences

Keywords

Animals, Antigens, Antigens: metabolism, Calcium, Calcium: metabolism, Cell Surface, Cell Surface: metabolism, C-Type, C-Type: metabolism, Edwardsiella ictaluri, Edwardsiella ictaluri: metabolism, Endocytosis, Endocytosis: physiology, Flow Cytometry, Fluorescein-5-isothiocyanate, Kidney, Kidney: cytology, Lectins, Mannose-Binding Lectins, Mannose-Binding Lectins: metabolism, Phagocytes, Phagocytes: metabolism, Pinocytosis, Receptors, Zebrafish, Zebrafish: metabolism

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