Cell-mediated and humoral immune responses in chickens infected with Salmonella typhimurium.

The cellular immune responses of leghorn and New Hampshire chickens following oral challenge at 4 weeks of age with Salmonella typhimurium were measured using assays for lymphocyte proliferative responses to mitogens and cytotoxic activity of natural killer (NK) cells. In addition, the humoral immune response to Newcastle disease virus (NDV) vaccine was assessed in S. typhimurium-infected chickens. At 8 and 20 days after infection with S. typhimurium, lymphocyte proliferative responses to various mitogens were significantly higher in S. typhimurium-infected chickens than in uninfected birds of the same breeds. Cytotoxic activity of NK cells was also significantly increased in infected birds on these days. Thirteen days after S. typhimurium infection, infected NDV-vaccinated chickens had higher antibody titers in response to NDV vaccination than uninfected vaccinated birds. NDV titers did not differ among groups at any other time of testing. These results show that both cellular and humoral immune functions are activated in the first 3 weeks following infection of 4-week-old chickens with S. typhimurium.