Lymphocyte subpopulations in lymphoid organs of rats after acute resistance exercise

Purpose: The ability of aerobic exercise to change lymphocyte subpopulation distributions is well documented; much less is known about resistance exercise. The purpose of this experiment was to determine the effects of an acute bout of resistance exercise on lymphocyte subpopulations in primary and secondary lymphoid compartments. Methods: Male rats were operantly conditioned to climb a ladder while carrying weights that were progressively increased to equal body weight. During the acute session, rats performed repetitive climbs until exhaustion. Thymus, spleen, blood, and axial and inguinal lymph nodes were removed; leukocytes were isolated and incubated with monoclonal antibodies against differentiation markers, activation antigens, and adhesion molecules. Results: Exercised versus control rats had greater numbers of leukocytes in the thymus, axial, and inguinal nodes but not in the blood or spleen. The percentage of CD4⁺ cells increased after exercise in the thymus, spleen, and blood. The percentages of calls expressing the integrin LFA-1β were elevated in all the tissues except inguinal lymph nodes. In addition, more leukocytes from exercised than nonexercised rats expressed detectable numbers of activation markers, IL-2 receptor-α and MHC class II molecules; however, as indicated by proliferating cell nuclear antigen analysis, the cells were not actively dividing at the time of assay. Conclusions: Based on these and published data, it appears that a single bout of resistance exercise can affect lymphoid cell subpopulations probably by inducing changes in leukocyte trafficking.