Predictable and Unpredictable Threat Immune Enhancement

Acute social stress has been associated with increased immune system activation. However, less is known about whether non-social acute stressors also impact the immune response. In addition, most studies examine stressors that contain multiple characteristics (e.g., social, unpredictable) that could contribute to an increased immune response, but few studies have attempted to disentangle these factors. Finally, few studies have examined whether simultaneous changes in affect are associated with changes in the immune response. The present study used a between-subjects design to examine immune system activation, via changes in salivary cytokines interleukin-6 (IL-6), IL-8, IL-1β, and tumour necrosis factor-α, in response to predictable and unpredictable electric shock. A multimodal assessment of changes in defencive motivation (startle reflex), attention (event-related potential probe N100, P300), and self-reported affect were evaluated to confirm the effectiveness of the threat manipulation. As expected, results indicated that the threat manipulation enhanced defencive motivation, attention, and self-reported affect. Across all participants, both predictable and unpredictable threat increased IL-8 but decreased IL-6. Greater changes in self-reported negative affect were associated with greater increases in the overall immune response. The present study suggests that acute non-social stress enhances immune system activation, particularly in those who experience greater changes in negative affect.