Heterophil Function in Healthy Chickens and in Chickens with Experimentally Induced Staphylococcal Tenosynovitis

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Abstract
Heterophil function was evaluated in 16 healthy chickens and in 46 chickens with experimentally induced staphylococcal tenosynovitis. In paired blood samples, heterophils from chickens with tenosynovitis had a significant increase in adherence, chemotaxis, phagocytosis, and bacterial killing of Staphylococcus aureus compared to heterophils from healthy chickens. The percent adherence of heterophils to nylon fiber columns increased significantly from a 78.4% mean ± 6.6% standard deviation to 87.6% ± 3.2% after induction of staphylococcal tenosynovitis. Heterophil movement following in vitro exposure to saline or endotoxin was increased in chickens with tenosynovitis; 3 ± 1 heterophils/0.25 mm2 to 10 ± 6 heterophils/0.25 mm2 and 136 ± 29 heterophils/0.25 mm2 to 340 ± 74 heterophils/0.25 mm2, respectively. Endotoxin-activated serum was chemoattractive for heterophils from all chickens. Flow cytometry was used to define the heterophil population on light scatter histograms, evaluate individual cell phagocytosis of latex beads, and quantitate the number of beads phagocytosed per heterophil. When incubated with increased numbers of beads, only heterophils from chickens with tenosynovitis phagocytosed higher numbers of beads. At heterophil to bead ratios of 1:10, the percentage of heterophils that phagocytosed beads increased from baseline values of 37.8% ± 9.0% to postinfection values of 67.3% ± 7.5%. Using 1:20 heterophil to bead ratios, heterophil phagocytosis increased from 38.7% ± 9.9% to post-infection values of 79.8% ± 7.3%. Heterophils from all chickens were able to phagocytose and kill log phase staphylococcal bacteria. After phagocytosis, the heterophils from chickens with staphylococcal tenosynovitis rapidly decreased the number of viable bacterial colony forming-units per milliliter by approximately one log. Circulating heterophils from chickens with experimentally induced staphylococcal tenosynovitis therefore appear to have increased functional capabilities in this bacterial inflammatory disease.