Cytotoxicity in Chicken Alimentary Secretions as Measured by a Derivative of the Tumor Necrosis Factor Assay

The host immune response to enteric bacterial infections, including salmonellosis, results in inflammatory cells entering the intestine near the site of infection. These cells produce factors, such as cytokines, that are cytotoxic to bacteria-infected cells, resulting in loss of host cells. In this study, an assay was developed, based on the tumor necrosis factor (TNF) assay, that measured the cytotoxic activity in alimentary secretions from chickens during a Salmonella enteritidis (SE) infection. Secretions were collected by pilocarpine-induced evacuation from the alimentary tract and clarified by centrifugation. Activity was assessed by the cytotoxic effect of secretions on chicken embryo fibroblasts as target cells. Cytotoxic activity from SE-infected hens was measured at intervals during the first 24 h following infection and daily for the next 10 d. The level of activity varied between hens but was maximal in secretions obtained at 24 h and 10 d after SE infection. Maximal levels of cytotoxic activity in alimentary secretions from hens occurred in response to a dose of 5x10(8) cfu/mL of SE. The cytotoxicity in secretions from SE-exposed hens that were deprived of feed was greater than those from control SE-exposed hens by more than fivefold.