Characterization of the innate and adaptive immunity to Salmonella enteritidis PT1 infection in four broiler lines

Four broiler lines were inoculated orally with Salmonella enteritidis phage type 1 at the age of 7 days (experiment A: lines 1 and 2) and at the age o f 1 day (experiment B: lines 3 and 4). At various days post-infection chick ens were sacrificed and the number of Salmonella in the caeca, liver, and s pleen were determined. Furthermore, phagocytic activity, cellular immune re sponses, and humoral responses were determined using, respectively, single- cell suspensions of spleen or intestine and serum. In both experiments, sim ilar trends were seen. Increased numbers of S. enteritidis were found in th e caeca of lines 1 and 3, whereas at the same time a decreased colonization was found in the spleen and in the liver, as compared to lines 2 and 4. In the latter two lines, the phagocytic activity of the phagocytes was higher and the humoral responses were lower. Observations from this study suggest that lower activity of phagocytes and higher humoral activity prevent syst emic S. enteritidis infection. (C) 2001 Elsevier Science B.V. All rights re served.