History of stress affects cell-mediated immunity

Open Access
Author:
Sprayberry, Kristen Maria
Area of Honors:
Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Tracy Lee Langkilde, Thesis Supervisor
  • James Harold Marden, Honors Advisor
Keywords:
  • cell-mediated immunity
  • PHA
  • phytohemagglutinin
  • fence lizards
  • fire ants
  • immunology
  • stress
  • glucocorticoids
  • corticosterone
Abstract:
Following exposure to stressors, energy resources are reallocated towards immediate responses, and diverted from functions such as the immune system. Which systems are suppressed may be altered by an animal’s evolutionary history. The eastern fence lizard (Sceloporus undulatus) is a native species impacted by the predatory invasive fire ant (Solenopsis invicta). We examined how history of invasion by fire ants and exposure to acute stress affected the cell-mediated immune response of post-gravid lizards. Lizards were captured from sites with long (>70 years) histories of fire ant invasion and correspondingly higher levels of corticosterone, and sites not yet invaded by these ants. All lizards were treated while gravid with either a physiologically relevant dose of the stress-relevant hormone corticosterone, to simulate the corticosterone response to a fire ant attack, or a vehicle control. We measured the cell-mediated immune response of females post-laying with the phytohemagglutinin skin test. We found that history of exposure to stress (associated with fire ant invasion) and the contemporary corticosterone treatment affected cell-mediated immune response. Lizards from high-stress fire ant invaded sites had reduced immune response compared to those from low-stress uninvaded sites. CORT-treated lizards from uninvaded sites also had decreased immune response when compared to control lizards from uninvaded sites, but CORT-treated lizards from invaded sites showed no difference when compared to control lizards from invaded sites. This suggests that evolutionary history of stress alters the immune response to short-term stress. Future work on how different branches of the immune system respond to environmentally-induced stressors will be informative for predicting and managing these threats.