RESUMEN
BACKGROUND: While it is well documented that immune responses, e.g. proliferative responses, can be influenced by psychosocial factors, e.g. stress, less is known about the biological mechanisms mediating such influences. The aim of the present investigation was to study the effect of an experimental stressor on mRNA levels in peripheral blood leukocytes of thymidylate synthase (TS), a gene necessary for cell division, while investigating possible individual differences in stress reactivity. METHODS: Fifteen healthy subjects were investigated under three experimental conditions: (1) exposure to a computerized mental stressor; (2) relaxation, and (3) control. Measurements included TS mRNA levels, total leukocyte number, leukocyte subtypes, and serum cortisol before (baseline), immediately after, and 1 h after each experimental condition. RESULTS: While no significant differences were found between experimental conditions at baseline in cortisol (p = 0.9) or TS mRNA levels (p = 0.1), significantly higher TS mRNA expression was found immediately after stress compared to pretreatment levels (p < 0.02). Changes in cortisol levels indicated an effect of the experimental stressor, with higher cortisol levels seen immediately after stress as compared to both relaxation (p < 0.01) and control (p < 0.01). Subjects who scored above the median on the Tellegen Absorption Scale showed significantly (p < 0.05) greater increases in cortisol and percentage of lymphocytes and significantly greater decreases in percentage of neutrophil cells after stress. CONCLUSION: The results suggest that TS mRNA levels in peripheral leukocytes may be sensitive to mental stress and confirm previous findings indicating that subjects scoring high on the personality trait of absorption exhibit greater physiological stress reactivity.