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 cells expressing the integrin LFA-1beta 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-alpha 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.

The effect of a 10-day space flight on the function, phenotype, and adhesion molecule expression of splenocytes and lymph node lymphocytes.

Previous studies have indicated that space flight affects the activation of lymphocytes from humans, monkeys, and rodents. In rats, where lymphocytes from blood, spleen, and lymph nodes have been tested, the accumulated data suggest that the effects of flight on various cells are lymphoid organ-specific. Thus, cells may be affected by variations in trafficking brought about by fluid shifts in microgravity (< 10(-3) g). In this study we examined lymphocyte activation (IL-2 production) as well as the expression of surface differentiation antigens and of adhesion molecules by splenocytes and lymph node lymphocytes (LNL) after a 10-day flight (Space Shuttle Mission STS-57). For splenocytes and LNL from flight (FLT) animals, IL-2 production decreased in response to the T cell receptor-independent mitogen 12-O-tetradecanoylphorbol-13-acetate plus ionomycin, but was not affected by stimulation with the T cell receptor-dependent mitogens Concanavalin A or phytohemagglutinin. In addition, the percentage, as well as fluorescent intensity, of splenocytes which expressed CD8, CD4, or kappa increased after flight. The percentage of LNL expressing CD2 also increased but those expressing CD5 decreased. The percentage of cells expressing the integrins LFA-1 alpha and beta increased with splenocytes from FLT animals but decreased for LNL. In contrast, FLT animals showed a decrease in the percentage of selectin-positive splenocytes. ICAM-1 expression did not change. In summary, these data are consistent with a model in which microgravity affects lymphocyte redistribution among organs, which in turn influences the activation potential of the cells.

Negative regulation of interleukin-2 production in primary lymphocytes by 12-O-tetradecanoylphorbol-13-acetate.

Stimulation of quiescent T lymphocytes to proliferate involves a complex series of events both between and within cells. At least 70 genes are known to be induced or activated from the time of the initial stimulation until DNA synthesis. While some of these gene products, e.g., interleukin-2 (IL-2) and IL-2 receptors, are required for proliferation, others, e.g., gamma-interferon and colony-stimulating factor, are ancillary to activated T cell function. Several biochemical signal transductions are among the early events. One of the earliest is phospholipase C-mediated hydrolysis of phosphatidylinositol leading to release of diacylglycerols and inositol phosphates, which in turn activate protein kinase C and elevate intracellular free calcium levels. The discovery that the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) both enhances proliferation and activates protein kinase C strengthens the evidence for a general role of protein kinase C in proliferation. Yet, the exact consequences of stimulation of protein kinase C in regard to specific proliferation proteins is still not clear. In this study, we present evidence that protein kinase C activation is directed to production of IL-2 but not to IL-2 receptors. Under conditions of TPA treatment in which protein kinase C was chronically reduced in T lymphocytes, IL-2 production was greatly depressed as were the level of IL-2 mRNA and [3H]thymidine incorporation. In contrast, these cells still expressed high affinity IL-2 receptors and proliferated when endogenous IL-2 was added. Because neither phosphatidylinositol metabolism nor Ca2+ flux was affected, the block appeared to be mediated directly or indirectly through protein kinase C.

DNA synthesis and production of interleukin 1 by lymph node macrophages in culture.

When bovine lymph node cells are cultured for several days the adherent macrophage population increases by as much as tenfold. This increase in cell number is primarily due to cell division, which reaches a maximum on day 4 or 5 of culture. Although the presence of the nonadherent cells seems required for cell division, we have been unable to detect a macrophage growth factor in either the nonadherent cell populations. The adherent cells were identified as macrophages based on positive esterase staining, the presence of Fc receptors, beta-glucuronidase activity, and phagocytosis. Moreover, these adherent cells produced interleukin 1 (IL1) after exposure to lipopolysaccharide in serum-free medium. Approximately 10(7) macrophages were stimulated to produce about 900 units of IL1 in a 24-hr period. Thus, the bovine lymph node preparation is a potential source of a large number of macrophages capable of dividing in culture and of producing IL1.

Visualization of protein kinases in lymphocytes stimulated to proliferate with concanavalin A or inhibited with a phorbol ester.

Stimulation of lymphocytes with a mitogenic lectin such as concanavalin A (ConA) results in differentiation and cell division. Among the changes which occur after stimulation are increases in phosphorylation of proteins and in protein kinase activity. We used a high-resolution, nondenaturing gel system to separate and visualize protein kinases in situ. We have clearly identified both autophosphorylating and substrate-dependent kinases. One band of cyclic AMP-dependent kinase activity was significantly enhanced in lectin-stimulated cells. In contrast, treatment of the cells with phorbol ester under conditions which depress stimulation caused a decrease in the activity of one kinase.