Abstract: The thymopeptdum is a well-characterized immunopotentiating hormone, thepresent experiments were designed to study whether thymopeptdum modulated theimmune system as an antistress factor. The controllable/uncontrollable footshock wereused as psychological stress. After 6 times of footshocks, 0.5hr per session, thehumoral immunity of uncontrollable old rats decreased signiflcantly, while the humoralimmunity of controllable rats was not significantly changed comparing to the controlgroup. The levels of glucocorticoid hormone of the two stress groups increasedheavily. The stressor controllability had influence on the levels of sertun IgG of rats.However, every other day for 6 times inhaperitoneally injections of thymopeptdumantagonized these changes, it improved humoral immunity of stressed fats, suppressedthe ascending trend of glucocorticoid hormone. The above mentioned resultsdemonstrated the thymopeptdum had antistress and antisenility effect.

Key words: thymopeptdum, psychological stress, antisenility, stressor controllability/uncontrollability, glucocorticoid hormone