title: Zebrafish kidney phagocytes utilize macropinocytosis and Ca+-dependent endocytic mechanisms.
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.
  
  
  RESULTS
  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
  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.
authors.affiliation: Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi, United States of America.
authors.forename: Claudia
authors.initials: C
authors.lastname: Hohn
authors.forename: Sang-Ryul
authors.initials: SR
authors.lastname: Lee
authors.forename: Lesya M
authors.initials: LM
authors.lastname: Pinchuk
authors.forename: Lora
authors.initials: L
authors.lastname: Petrie-Hanson
mesh_terms: D000818:Animals; D000941:Antigens / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D020610:Edwardsiella ictaluri / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate; D007668:Kidney / Q000166:cytology*; D037181:Lectins, C-Type / Q000378:metabolism; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000378:metabolism; D010586:Phagocytes / Q000378:metabolism*; D010873:Pinocytosis; D011956:Receptors, Cell Surface / Q000378:metabolism; D015027:Zebrafish / Q000378:metabolism
chemical_list: D000941:Antigens; D037181:Lectins, C-Type; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D011956:Receptors, Cell Surface; D016650:Fluorescein-5-isothiocyanate; D002118:Calcium