Bactericidal antibody response in the Pacific hagfish, Eptatretus stoutii

The hagfish, Eptatretus stoutii, has been shown to synthesize bactericidal antibodies after injections of gram-negative organisms. These bactericidins could be detected as early as 2 days after the primary injection. Secondary responses were accelerated, although titers were not significantly higher than those reached in the primary response. The bactericidins of hagfish were found to react with other gramnegative enteric bacteria, but not with gram-positive strains. The bactericidins show a lesser degree of specificity and a shorter induction period than other hagfish antibodies or most antibodies induced in higher vertebrates. The bactericidal activity was temperature dependent and could be irreversibly destroyed by heating at 50 C for 20 min. Immune sera were subjected to gel filtration on Sephadex G-200, and bactericidal activity was found to be associated with the excluded peak indicating a high-molecular-weight component. Evidence indicates that inducible immune responses of this bactericidal type represent a primitive capacity which arose before the emergence of vertebrate species.