Exercise stress alters murine lymphocyte subset distribution in spleen, lymph nodes and thymus

Our previous work indicated that exercise stress in mice was associated with reduced splenic lymphocyte proliferation to T cell mitogens. The purpose of this study was to determine the effect of acute exercise stress and exercise training on the phenotype distribution of murine lymphocytes in the spleen, lymph nodes and thymus. In mice given an exhaustive bout of treadmill exercise, the percentage of Thy 1.2 and Lyt2 antigen bearing cells decreased in the thymus, but the percentage of L3T4-positive cells did not change significantly. Acute exercise did not alter the percentage of Thy1.2, L3T4 or Lyt2-positive cells in the secondary lymphoid compartments (nodes, spleen). By contrast, in mice given a chronic exercise training programme (8 weeks duration; 30 m/min, 8 degrees slope, 30 min/session, 5 daily sessions/week) followed by a 72 h rest period, the percentage of L3T4-positive cells increased by 53% in the spleen, 19% in the lymph nodes and 29% in the thymus compared with sedentary controls; no parallel increase in the percentage of Thy1.2 antigen bearing cells was observed. These results suggest that the effect of exercise on the frequencies of lymphocyte subpopulations in murine lymphoid compartments is dependent upon the chronicity of the stress and probably on the accompanying physiological adaptations to the stress.