S4.2-2 Sunday, Jan. 5 11:00 Stress/immune interactions: A pathological relationship or an adaptive response to adverse conditions? ADAMO, Shelley A; Dalhousie Univ., Halifax email@example.com
Both the stress response and immune response defend animals against organisms that can cause catastrophic declines in fitness. When resources are abundant, having these two systems work synergistically with each other would seem adaptive. However, negative interactions between the stress and immune responses are common and phylogenetically widespread even under ad lib conditions. It seems unlikely that these negative interactions are simply pathological as they are partly driven by stress hormone effects on immune cells. In crickets (Gryllus texensis), the stress neurohormone octopamine shifts molecular resources towards flight-or-fight (e.g. the protein apolipophorin III), while at the same time altering immune cell activity to minimize the impact of this molecular theft (e.g. increased immune cell phagocytosis). There is also a shift away from immune responses that generate high levels of reactive molecules (e.g. phenoloxidase activity and nitric oxide production) and a shift towards responses that rely on other mechanisms such as lysozyme-like activity. Both the stress response and immune response increase the level of lipid peroxides in the hemolymph (blood) of G. texensis, suggesting increased oxidative stress. Reducing the production of reactive molecules by the immune system during an on-going stress response probably reduces immunopathology due to oxidative stress. Although these stress hormone-induced changes to immune function result in an overall decline in resistance to disease, without them the decline in disease resistance would be steeper and immunopathology would be greater when conditions are suboptimal.