Lack of a bactericidal response in the earthworm Lumbricus terrestris after immunization with bacterial antigens

To determine whether the earthworm Lumbricus terrestris could show a bactericidal response, 775 worms were injected with various bacterial antigens: (a) five bacterial strains isolated from the slime and gut cavity of earthworms, (b) a gram-negative bacillus (EMB-1) from a representative crustacean and (c) Salmonella typhosa H antigen. Controls consisted of worms injected with 0.85% saline, formalized saline at 0.3%, and shams which were only punctured with a needle without injection of any antigen. Responses were looked for after 12 hr and 7 days at antigenic concentrations of 10 6 and 10 8 cells. In addition, one antigen (L-1) was injected at concentrations of 10 4 and 10 6 cells. Worms challenged initially with the highest doses were injected again for secondary responses and tested 33–42 days later. Bactericidal responses assayed by means of the Schwab and Reeves technique were not observed in any of the experimental groups. Although earthworms are capable of specific apparently cellular responses to allogeneic and xenogeneic tissue antigens, they seem to be incapable of synthesizing detectable humoral substances to certain bacterial antigens.