title: The cytochemical and ultrastructural characteristics of phagocytes in the Pacific oyster Crassostrea gigas.
abstract: Phagocytes have been proved to play vital roles in the innate immune response. However, the cellular characteristics of phagocytes in invertebrates, especially in molluscs, remain largely unknown. In the present study, fluorescence activated cell sorting (FACS) was employed to sort the phagocytes from the non-phagocytic haemocytes of the Pacific oyster Crassostrea gigas. The cytochemical staining analysis revealed that phagocytes were positive staining for α-naphthyl acetate esterase and myeloperoxidase, while negative staining for toluidine blue and periodic acid-Schiff. The non-phagocytic haemocytes exhibited positive staining for periodic acid-Schiff, weak positive staining for toluidine blue, but negative staining for α-naphthyl acetate esterase and myeloperoxidase. In addition, phagocytes exhibited ultrastructural cellular features similar to those of macrophages, with large cell diameter, rough cell membrane and extended pseudopodia revealed by the scanning electron microscopy, while the non-phagocytic haemocytes exhibited small cell diameter, smooth cell surface and round spherical shape. Transmission electron microscopy further demonstrated that phagocytes were abundant of cytoplasmic bodies and mitochondria, while non-phagocytic haemocytes were characterized as the comparatively large cell nucleus with contorted and condensed heterochromatin adherent to the nuclear envelope. Moreover, compared with non-phagocytic haemocytes, phagocytes exhibited significantly higher levels of intracellular cytokines, including tumor necrosis factor, interferon-like protein and interleukin-17, and significantly higher abundance of lysosome and reactive oxygen species, which were of great importance to the activation of immune response and pathogen clearance. Taken together, these findings revealed the different cytochemical and ultrastructural features between phagocytes and non-phagocytic haemocytes in C. gigas, which would provide an important clue to investigate the mechanism of phagocytosis underlying the innate immune response.
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Zhihao
authors.initials: Z
authors.lastname: Jia
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Lusheng
authors.initials: L
authors.lastname: Xin
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China.
authors.forename: Ran
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Weilin
authors.initials: W
authors.lastname: Wang
authors.affiliation: Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian, 116023, China.
authors.forename: Lingling
authors.initials: L
authors.lastname: Wang
authors.affiliation: Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian Ocean University, Dalian, 116023, China. Electronic address: lshsong@dlou.edu.cn.
authors.forename: Linsheng
authors.initials: L
authors.lastname: Song
mesh_terms: D000818:Animals; D002469:Cell Separation; D049896:Crassostrea / Q000166:cytology* / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D016207:Cytokines / Q000235:genetics* / Q000378:metabolism; D005434:Flow Cytometry; D007372:Interferons / Q000235:genetics / Q000378:metabolism; D020381:Interleukin-17 / Q000235:genetics / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D010586:Phagocytes / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D017382:Reactive Oxygen Species / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
chemical_list: D016207:Cytokines; D020381:Interleukin-17; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D007372:Interferons
keywords: Crassostrea gigas; Cytochemical staining; Cytokine; Lysosome; Phagocyte; Reactive oxygen species; Ultrastructural analysis