[Antibacterial resistance induced by injection of ascitic fluid (with IgM partially removed) and natural monoclonal antibodies of human origin in rainbow trout].

Human monoclonal immunoglobulins M from myeloma shown to have the typical polyspecificity of natural antibodies, were precipitated from the ascitic fluid that originally contained them. The IgM and their supernatant were injected in parallel, intraperitoneally into rainbow trout (Oncorhynchus mykiss) to test passive protection against experimental furunculosis. Protection was observed in both cases (significant protection at 2%). However, only trout treated with IgM were still protected against polybacterial cross-infections which occurred 10 days later (significant protection at 1%). These results confirm the passive mammalian protection conferred by biologic fluids injected in vivo in fish and provide further evidence for participation of natural antibodies in antibacterial defences.