STRESS EXACERBATES AGE-RELATED DECREMENTS IN THE IMMUNE-RESPONSE TO AN EXPERIMENTAL INFLUENZA VIRAL-INFECTION

To test the hypothesis that stress exacerbates immune decrements assoc iated with aging, the impact of restraint stress on immunosenescence w as assessed using an experimental model of influenza A/Puerto Rico/8/3 4 viral infection. Beginning one day prior to infection, male B57BL/6 mice, 3 and 22 months of age, were subjected nightly to 12 hours of re straint stress. In both age groups, restraint induced a comparable inc rease in serum corticosterone levels. However, in contrast to the 3-mo nth-old controls, serum corticosterone levels in 22-month-old mice ret urned to baseline slower after removal of the stressor. The characteri stic influenza-driven increase in cellularity of the lung and draining lymph node was decreased by age and further suppressed by stress. Nat ural killer cell activity and virus-specific T helper cell function we re also blunted by age and almost completely abrogated by stress. Furt hermore, due to the weak immune response to viral infection, aged anim als subjected to stress had a lower survival rate than age-matched con trols.