Leukocyte Response to Intra-Abdominal Infection in One Day Old Leghorn Chickens.

Using a previously characterized and described abdominal model to define the avian immune response to intra-abdominal challenge in chickens, we have adapted this technique for the study of chickens' immune response to a intra-abdominal challenge. The intra-abdominal infection model facilitates the characterization of peripheral blood leukocyte dynamics and abdominal cell infiltrates. Day-of-hatch Leghorn chickens were injected intra-abdominally (IA) with [(CJ)1 × 10 colony-forming units (CFUs)]. Changes in peripheral blood leukocyte numbers and abdominal cell infiltrates were monitored at 0, 4, 8, and 24 h post-injection. Peripheral blood leukocyte numbers were also determined for 2 h post-injection. For mortality studies, birds were injected intra-abdominally with 1 × 10 CFUs CJ and mortalities were recorded for 72 h post-injection. In the peripheral blood of CJ-injected chicks, total white blood cell (WBC) numbers began increasing by 2 h post-injection, peaking at 4 h post-injection with the predominant cell type being polymorphonuclear leukocytes (heterophils). Total WBCs declined after 8 h and this decline continued at 24 h, with total WBC numbers approaching control values. The injection of CJ into the abdominal cavity caused a rapid rise in abdominal cell infiltrates with the predominant infiltrating leukocytes being heterophils. Peak abdominal heterophil infiltrates were observed at 8 h post-injection, declining only slightly by 24 h post-injection. Mortality in the CJ challenge groups reached 37%. Mortality in the positive control groups were greater than 50%. The data suggest that infection does stimulate the innate immune response in chickens when administered IA, however, the immune response and infection is not characterized with the high levels of mortality observed with a infection. These data provide a basis for a more definitive characterization of chickens' immune response to and a model to evaluate intervention strategies to prevent the infection and colonization of poultry.