Inducible lectins with galectin properties and human IL1 alpha epitopes opsonize yeast during the inflammatory response of the ascidian Ciona intestinalis
Hemocytes from the ascidian Ciona intestinalis exert in vitro Ca2+-dependent cytotoxic activity
toward mammalian erythrocytes and K562 cells. To examine the lytic mechanism, hemocyte
populations were separated (B1-B6 bands) through a Percoll discontinuous density gradient, the
hemocyte cytotoxic activity (HCA) and the lytic activity of the hemocyte lysate supernatant (HLS)
were assayed. In addition the separated hemocytes were cultured and the cell free medium (CFM)
assayed after 3h culture. Results support that unilocular refractile hemocytes (URGs), enriched in
B5, are cytotoxic. The B5-HLS contains lysins and the activity of B5-CFM shows that lysisns can
be released into a culture medium. The B5 activity was blocked by D-Galactose, α-Lactose,
Lactulose, LacNAc, thiodigalactoside (TDG), L-Fucose, D-Mannose, D-Glucose, sphingomyelin
(SM), and soluble phospholipase A2 (sPLA2) inhibitors (dibucain, quinacrine). Accordingly, HLS
chemico-physical properties (alkaline medium, high termostability, Ca2+-dependence, trypsin
treatment, protease inhibitors) and SEM observations of the affected targets suggested that sPLA2
could be responsible for changes and large alterations of the target cell membrane. An apoptotic
activity, as recorded by a caspase 3, 7 assay, was found by treating K562 cells with very diluted
HLS. A lytic mechanism involving sPLA2 and lectins promptly released by URGs and morula cells
respectively is suggested, whereas target cell membrane SM could be a modulator of the enzyme
activity