Vicarious trauma primes innate immunity and reconfigures human brain networks

Vicarious trauma--witnessing serious harm to others--produces systemic neuroimmune effects in animal models. However, its brain, autonomic, and immune consequences in humans remain unclear. We scanned 88 participants with fMRI during a naturalistic movie-viewing paradigm depicting either industrial cruelty to farm animals (Vicarious Trauma, VT) or positive human-animal interactions (Vicarious Community, VC) with concurrent autonomic physiology and gene expression in circulating monocytes. VT, compared to VC, evoked sustained sympathetic arousal lasting 40 minutes post-viewing and primed innate immune cells to elicit elevated pro-inflammatory (upregulating IL1B and CXCL8) and reduced anti-inflammatory (TGFB1) responses. VT reduced integration in a frontoparietal control system and increased coupling between a salience/action-mode system with paralimbic, basal ganglia, and sensorimotor regions. Disrupted negative coupling between frontoparietal/default-mode and hippocampal systems predicted VT-related CXCL8 increases. These findings shed light on how the brain translates vicarious trauma into the priming of innate immunity.