Comparative immunology: sipunculid bactericidal responses.

This report continues comparative studies of inducible bactericidins of invertebrates. The bactericidin of the sipunculid worm Dendrostomum zostericolum Chamberlain was induced by intracoelomic injections of killed bacteria. With the assay system used, optimal results were obtained with 90 min of incubation at 20 to 35 C. Bactericidal titers in coelomic fluids from noninjected worms were either low or nonexistent. After injections of gram-negative bacteria, bactericidal titers of up to 1:1280 were reached within 7 days. Considerable individual variations were noted. Optimal stimulation was achieved with 4 x 10(8) bacteria per injection. The response was relatively nonspecific as measured by cross-immunization and absorption experiments. Injections of sterile sea water produced no response. Coelomic fluids could be inactivated by heating at 50 or 56 C for 20 min. Activity was not restored by a pool of unheated coelomic fluid from nonimmunized worms. The significance of these observations was discussed with reference to immunity of sipunculids and to comparative immunology.