Age-related enhancement and suppression of a T-cell-dependent antibody response following stressor exposure

The effects of uncontrollable footshock on the peak splenic plaque-forming cell (PFC) response and serum antibody titers to sheep red blood cells (10(6) cells ip) were assessed in 3-month-old and 9-month-old male CD-1 mice. Exposure to uncontrollable footshock provoked an immunosuppression in mice of both age groups. The critical period for the induction of the suppression (i.e., 72 hr after inoculation) did not differ between the 3-month-old and 9-month-old mice; however, the suppression could be provoked more readily in the older animals. In the 9-month-old mice, the variations of immune activity were dependent on the severity of the stressor and the time of stressor application. Specifically, in contrast to the suppression induced by footshock, a relatively mild stressor such as exposure to a novel environment effectively increased the PFC response. A marked enhancement of the PFC response and antibody titers was evident in older animals that were shocked immediately or 24 hr after inoculation. The possibility exists that stressor application in older mice may influence regulatory processes that are associated with an immune response and that the nature of these regulatory mechanisms may vary with the time after antigenic challenge.