Study Rationale: The acute stress response induces immunosuppression; however, this relationship has been studied in arbitrary models only (shock avoidance, job interview). This study employs the novel approach of examining stress and immune responses to a personally relevant stressor (pain); prior studies used arbitrary models only (shock avoidance, job interview). Pain offers a highly salient and personal context well-suited for investigation of negative cognitive perseveration. Pain is acutely sensitive to exacerbation via inflammation, and thus the relevance of examining immune effects of rumination on future negative expectations ("expecting the worst") is underscored.