title: Ultrastructural localization of highly variable 185/333 immune response proteins in the coelomocytes of the sea urchin, Heliocidaris erythrogramma.
abstract: The 185/333 proteins of sea urchins represent a family of highly variable immune response molecules with unknown functions. In this study, we show that 185/333 proteins are expressed by three cell types: amoebocytes, colourless spherule cells and gut-associated amoebocytes. A sub-population of amoebocytes express 185/333 proteins on the membranes of vesicles emanating from the trans-Golgi and which later fuse with the plasma membranes of the cells. The previously uncharacterized gut-associated amoebocytes also show a high level of 185/333 protein expression on their internal vesicles and plasma membranes. Colourless spherule cells contain 185/333 proteins within large spherules (specialized intracellular vesicles). In the presence of bacteria and yeast, the ultrastucture of colourless spherule cells changes and 185/333 proteins disappear. In contrast, 185/333 proteins were not found in the phagosomes of coelomocytes. The 185/333-positive gut amoebocytes were often associated with anuclear bodies, which appeared to incorporate material of microbial origin that was surrounded by 185/333 proteins. The association between 185/333 proteins on gut amoebocytes and anuclear bodies suggests that these proteins may be involved in the phagocytosis of microbes in the gut epithelium.
authors.affiliation: Department of Biological Sciences, Macquarie University, North Ryde, New South Wales, Australia. nolwenn.dheilly@univ-perp.fr
authors.forename: Nolwenn M
authors.initials: NM
authors.lastname: Dheilly
authors.forename: Debra
authors.initials: D
authors.lastname: Birch
authors.forename: Sham V
authors.initials: SV
authors.lastname: Nair
authors.forename: David A
authors.initials: DA
authors.lastname: Raftos
mesh_terms: D000818:Animals; D047329:Anthocidaris / Q000276:immunology* / Q000378:metabolism / Q000648:ultrastructure; D002462:Cell Membrane / Q000276:immunology; D022162:Cytoplasmic Vesicles / Q000276:immunology / Q000648:ultrastructure; D004064:Digestive System / Q000276:immunology / Q000378:metabolism; D007413:Intestinal Mucosa / Q000276:immunology / Q000648:ultrastructure; D008565:Membrane Proteins / Q000276:immunology* / Q000378:metabolism*; D010586:Phagocytes / Q000276:immunology / Q000378:metabolism; D010587:Phagocytosis
chemical_list: D008565:Membrane Proteins