[Scanning electron microscopic observation of mouse ascitic carcinoma cells after intraperitoneal administration of lentinan].

Direct action of lentinan (LNT) on tumor cells in an in vivo system was observed by scanning electron microscopy. LNT was injected intraperitoneally 7 consecutive days (0.1 mg/mouse/day) in to C3H/He mice along with MM2 ascitic carcinoma cells. MM2 tumor cells adhering to the peritoneal wall were examined every day until the day after the last LNT injection, and compared with cells of non-treated tumor bearing mice. On the day after the first LNT injection, LNT was observed as granulated material both on the tumor cells, which were degenerated and on the mesothelial cells, which were not changed. On the 7th day, almost all tumor cells were seen to be surrounded by many lymphocytes in the LNT-treated mice. Retention of ascitic fluid and fibrin deposition were almost the same as or less than in non-treated mice. From these results, it is suggested that direct action of LNT on tumor cells contributed to enhancement of antitumor immunity, although LNT did not have direct killing activity against tumor cells.