Isoprinosine as an immunopotentiator in an animal model of human osteosarcoma

The effects of isoprinosine (ISO) on the immune responses (Con A-induced lymphocyte proliferation, monocyte chemotactic responsiveness, and "natural killer" cytotoxicity) of normal hamsters and hamsters with human osteosarcoma (OS) were investigated. Human osteosarcoma was induced in newborn inbred hamsters (LHX/SsLAK) after induction of tolerance in utero. In vitro, ISO increased Con A-induced proliferation of peripheral blood lymphocytes (PBL) from normal hamsters by 23.4-48.9% and from OS-bearing hamsters by 58.1-107.4% over controls (Con A alone). When ISO was administered in vivo by intraperitoneal injection. Con A-induced proliferation of PBL from both normal and OS-bearing recipients in vitro was increased by 50-55% at 1, 3 and 5 days after injection. The chemotactic responsiveness of monocytes from OS-bearing hamsters was also significantly increased (59.1-97.4%) at 1, 3 and 5 days after injection of ISO. Natural killer cytotoxicity was augmented at 1, 3 and 5 days after injection of ISO by 31.7-83.6% in normal hamsters and 54.6-184% in OS-bearing hamsters. These results indicate that ISO can produce a generalized enhancement of immune function in hamsters with OS.