Exercise Modulates Lymphocyte Homing In Peripheral Lymphoid Organs

Abstract

Exercise induces considerable physiological changes in the immune cell count. Lymphocyte counts in the peripheral blood increase during exercise, while there is a post-exercise lymphopenia. However, there are nearly no data available on lymphocyte recirculation to peripheral lymphoid organs. PURPOSE Therefore, the aim of the study was to determine the source and the destination of lymphocytes recruited to the peripheral blood during acute exercise. METHODS Lymphocytes were isolated and labelled with a fluorescent dye (Cell-Tracker Green) and injected intravenously in male Swiss mice. One group performed an acute treadmill exercise at 80% VO2max. The other group of sedentary animals served as controls. After the test, thymus, bone-marrow, spleen, lung, liver, peyer's patches and lymph nodes were excised and used for preparing thin sections or for lymphocyte isolation. Lymphocyte distribution was investigated both qualitatively and quantitatively using either fluorescence-microscopy or flow-cytometry, respectively. RESULTS After exercise lymphocyte percentage in the spleen (−25%), the liver (−12,5%) and the bone-marrow (−22%) decreased suggesting an exercise induced release of lymphocytes. In contrast, lymphocytes seemed to be pooled in the lymph nodes (+8%), the peyer's patches (+100%) and the lung (+24%). CONCLUSIONS Acute exercise affects lymphocyte recirculation and leads to a different distribution-pattern in the peripheral lymphoid organs. Spleen, liver and bone-marrow release lymphocytes into the circulation during exercise, followed by redistribution into the lymph nodes, the peyer's patches and the lung, where the probability for subsequent antigen contacts might be increased.