LYMPHOCYTE RECIRCULATION, EXERCISE, AND IMMUNE-RESPONSES

Alterations in leukocyte concentrations in the blood are associated wi th exercise, stress, and other pathophysiological perturbations. The c ontinuous migration and redistribution of cells of the recirculating l ymphocyte pool between the blood and lymphatic systems can be influenc ed by a variety of physiological, immunological, and pathological proc esses. The phenotypic distribution of lymphocyte subsets is not the sa me in blood, afferent lymph, and efferent lymph, and cell-tracking exp eriments have shown that lymphocytes vary in their migratory propertie s. The most comprehensive physiological studies tracking these cells i n vivo have been done in sheep. It has been shown that lymph-derived c ells have different migratory capacities than blood-derived lymphocyte s, that antigenic challenge of a single lymph node can first reduce th e output of lymphocytes from the node and then markedly increase the r ecruitment from the blood and subsequently the output into efferent ly mph. In most mammals, the blood pool of lymphocytes represents only ab out 1% of the total lymphocytes and only a small fraction of the recir culating lymphocyte pool. Therefore, testing the effects of exercise o n lymphocyte recirculation by examining blood samples only requires co nsiderable deduction and inference to interpret multicompartmental eff ects.