ARS | Publication request: THE EFFECTS OF DEXAMETHASONE IMMUNOSUPPRESSION ON BACTERICIDAL ACTIVITY OF TURKEY MONOCYTES

Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: May 30, 1999
Publication Date: N/A

Technical Abstract: Female turkeys appear to be more resistant to respiratory infections associated with stress-induced immunosuppression than are male turkeys. In order to determine the mechanism of this resistance, male and female turkeys were treated with 3 intramuscular injections of dexamethasone (DEX) at 0, 0.5 and 2.0 mg/Kg body weight on alternate days. Twenty-four hours after the third injection birds were bled and white blood cell (WBC) differentials of individual birds were determined. Pooled samples of glass-adherent mononuclear cells were cultured, challenged with Escherichia coli, and stained. The antibacterial activity of monocytes was quantitated by monitoring the percentage of cells infected over time. Dexamethasone at both 0.5 and 2.0 mg/Kg significantly (P </= 0.05) decreased phagocytic activity in females only. Antibacterial activity was significantly decreased at both concentrations of DEX 8 and 16 hours post-infection in both sexes and was significantly lower in males as compared to females. Total WBC counts were significantly increased in females at both concentrations of DEX whereas male total counts were unaffected. Both males and females had a significant increase in the heterophil to lymphocyte ratio. Within the same study, replicate pens of turkeys were challenged with intra-air sac inoculation of E. coli. Mortality was significantly increased only in male birds treated with 2.0 mg/Kg DEX as compared to females. These results indicate sex-related differences in the stress response of turkeys that may affect macrophage function and resistance to opportunistic bacterial infection.