Tasuku Watanabe

CELL CULTURE AND SOME PROPERTIES OF FISH IMMUNOCYTES

The importance of the in vitro cultures of animal cells with their proper functions has been well recognized. There have been many trials on the cell culture maintaining their proper and sustainable functions. There are also many studies using such cell systems. The recent studies on immunocyte cultures reveal that cultured immunocytes provide adequate research systems for the investigations both of cytokine characterizations and their roles in immunobiology and host defense (Papadimitriou 1989, van Furth 1992). Especially, the intensive studies on chemoatractant cytokines (chemokines), such as interleukin 8 and macrophage inflammatory protein, provided tools for the definition of inflammation in molecular level (Baggiolini 1994). Most of such studies were performed using macrophage cell lines in mammals. There have also been several attempts on the cell culture of fish immunocytes. This overview describes the recent studies and their characteristics upon the trials of fish immunocyte cultures including our works.

Fine Structure of the Normal and Virus-infected Cells Derived from the Kidney of Yamame, Oncorhynchus masou

The normal and virus-infected cells of the cell line, YNK, derived from the kidney of Yamame, Oncorhynchus masou, were studied at the ultrastructural level. The spindle-shaped YNK cells had an elongated nucleus with one or two nucleoli. Very prominent desmosomes were often seen between two neighbouring cells. The cells had a well developed rough-surfaced endoplasmic reticulum (rER) and numerous mitochondria. Many small vasicular invaginations, one of the characteristics of active pinocytotic cells, were seen adjacent to the cell membrane. These properties suggest that YNK cells were derived from the epithelium of the distal tubules of the collecting tubules of Yamame kidney. YNK cells had at least 10 times the sensitivity of RTG-2 cells to the infectious pancreatic necrosis virus. The virus particles were found in the cisternae of the well developed rER. Those facts sugest that the main target cells of the virus are the epithelial cells with well developed rER, such as pancreatic aciner cells, renal tubular epithelial cells, and liver parenchymal cells. YNK cells also had as much sensitivity against the infectious hematopoietic necrosis virus as that of RTG-2 cells. Numerous virus particles were found in intercellular spaces, and were matured by budding from the plasma membrane.