Splenic immune responses following treadmill exercise in mice.

The in vitro proliferation response to lipopolysaccharide and pokeweek mitogen by splenic lymphocytes and the effect on the total splenic lymphocyte number were examined in C57BL/6J mice following an 8-week treadmill training program (30 m/min, 8 degrees slope, 30 min/day, 5 times/week) and after a single bout of exhaustive exercise (50% stepwise increases in final running speed for 10-min intervals). Plasma corticosterone levels were also measured to evaluate whether changes in adrenocortical activation were associated with exercise-induced immunomodulation. In comparison to sedentary controls, trained mice had an increase of 35% in succinate dehydrogenase activity per unit of protein in the quadriceps femoris muscle. Trained mice showed an increase in splenic lymphocyte proliferation to both mitogens which was evident 72 h after completion of the final training session, relative to sedentary controls. Immediately following exercise, however, lymphocyte proliferative responses were depressed compared with the training and the control values. The exercise regimen resulted in a reduction in total number of mononuclear cells per spleen. Changes in plasma corticosterone levels after exercise were not clearly associated with immunodepression or immunoenhancement of splenic lymphocyte mitogenesis. Taken together, the data suggest that moderate endurance training augments splenic B lymphocyte mitogenesis and further, that the immediate effects of exercise on splenic immune function vary with the duration and intensity of the work.