We have shown previously that increased resistance to Salmonella enteritidis (SE) organ infectivity in 1-day-old chicks was conferred by the immunoprophylactic administration of SE-immune lymphokines (SEILK). These lymphokines have been found to be present in the cell culture media of concanavalin A-stimulated splenic lymphocytes obtained from SE-immunized chickens. In the present study we evaluated whether turkeys also produced SEILK and whether these lymphokines could protect 1-day-old chicks and turkey poults against SE liver invasion. In addition, we tested the ability of our original chicken SEILK to reduce SE liver invasion in turkey poults. Day-of-hatch chicks and turkey poults were injected intraperitoneally with immune lymphokines of either chicken or turkey origin. One hour later the birds were challenged per os with SE, and 20 hours later their livers were examined by bacteriological methods for the presence of SE. We found that SEILK induced from the splenic lymphocytes of SE-immunized turkeys reduced SE liver invasion in both chicks and turkey poults. Conversely, we also determined that SEILK produced by chicken splenic lymphocytes conferred protection against invasion by SE in turkey poults. This research is the first report of the production of SEILK in turkeys and also the first report on the cross-species activity of these effector molecules in chickens and turkeys.