A distinct immune cytokine profile is associated with morning cortisol and repeated stress

The objective of this study was to investigate possible immune cytokine trends throughout a week-long surgical simulation mass-casualty training session in order to determine the effects of stress inoculation on the immune system.

Thirty-seven military medical students participated in a hyper-realistic surgical simulation training event conducted at Strategic Operations site in San Diego, California. Salivary samples were collected every morning of the stress training exercise for 4 consecutive days. Cortisol, along with a panel of 42 immune cytokines, was measured using multiplex enzyme-linked immunosorbent assays from Eve Technologies. The determined concentrations were averaged and plotted on a scatter plot, and then points were fit to a second-order polynomial trendline of best fit to measure.

The cytokines epidermal growth factor, growth-related oncogene-α, interleukin (IL)-1α, and platelet-derived growth factor-AA followed a noted pattern of cortisol decrease throughout the week. In addition, cytokines IL-27, granulocyte colony stimulating factor, IL-10, and IL-13 demonstrated a late peak, followed by a return to baseline at the conclusion of training. Finally, the cytokine monocyte chemoattractant protein-1 displayed a decline throughout the week followed by an increase on the last day of stress training.

Altogether, these results help to identify important biomarkers that may help to improve long-term stress adaptation and prevent post-traumatic stress disorder following exposure to repeated stress.