The elderly population is at an unprecedented risk of infectious diseases and malignancy due to apparently inevitable age-related declines in immunity. The 'immune risk profile' (IRP) is an array of biomarkers that has been used to predict morbidity and mortality in older adults. As it is generally accepted that middle-aged and elderly individuals who habitually participate in moderate-intensity exercise are less likely to incur an infection than their sedentary counterparts, this review addresses current knowledge on the effects of regular exercise on aspects of adaptive immunity as they relate to the IRP. Findings from cross-sectional studies mostly show enhanced immunity in physically active compared to sedentary older adults. These include greater T-cell responsiveness to mitogens in vitro, a reduced frequency of antigen- experienced and senescent T-cells (i.e. CD45RO+/KLRG1+/CD57+/CD28-), enhanced IL-2 production and Tlymphocyte expression of the IL-2 receptor, longer chromosome telomere lengths in blood leukocytes and in vivo immune responses to vaccines and recall antigens. In contrast, the evidence from the available longitudinal studies that have used an exercise training intervention in previously sedentary elderly to improve similar immune responses is less compelling. Although this might indicate that exercise has limited immune restorative properties in previously sedentary elderly, there are still relatively few studies that have addressed specific IRP criteria and the large variation in experimental design among the longitudinal studies complicates the juxtaposition of these results. It is clear that a more substantial and focused research approach is required before physical exercise can be used in earnest as an effective immune restorative strategy in the elderly. This mini-review summarizes the major findings of these studies and proposes future avenues of research to investigate the effects of regular exercise on aspects of adaptive immunity in the elderly as they relate to the IRP. Copyright (C) 2009 S. Karger AG, Basel

PURPOSE: Acute exercise alters the activation status of blood T-cells, evident by changes in the cell surface expression of the early T-cell activation marker CD69. The killer cell lectin-like receptor G1 (KLRG1) is expressed on antigen-experienced T-cells which are unable to clonally expand in response to an antigenic stimulus but are capable of immediate effector functions such as recognizing and killing virally infected cells. T-cells expressing KLRG1 are preferentially mobilized into the peripheral blood in response to acute exercise, which could affect the overall activation status of blood T-cells. METHODS: Ten trained males (age: 24.6 ± 4.8; height: 183.1 ± 6.7cm; mass: 72.8 ± 7.9kg; VO2max; 61.3 ± 5.9 ml·kg-1·min-1) ran at 80% VO2max until exhaustion (time: 36.1 ± 5.8 minutes). Using monoclonal antibodies and 4-colour flow cytometry, blood lymphocytes isolated before (PRE), immediately after (POST) and 1 hour after (1H) exercise were analyzed for KLRG1 and CD69 co-expression on CD3+/CD4+ and CD3+/CD8+ T-lymphocytes in response to the exercise challenge and after 4h stimulation in culture at 37°c with and without the mitogen PMA. RESULTS: The proportions of KLRG1+ cells among total CD4+ and CD8+ T-cells increased by 17% and 25.2% respectively at POST, with CD8+ T-cells falling below PRE values at 1H. CD69 expression on CD4+ and CD8+ T-cells was unaffected by cell culture or the exercise challenge. When stimulated with PMA, the expression of CD69 at POST increased by 16.7% on CD4+, but decreased by 6.9% on CD8+ T-cells. KLRG1+ cells expressed higher levels of CD69 than KLRG1- cells in both CD4+ and CD8+ T-cells for all stimulated samples. CD69 expression was unaltered by exercise on either KLRG1+ or KLRG1-/CD4+ T-cells. In contrast, CD69 expression fell by 11.7% on KLRG1+/CD8+ T-cells POST. No changes in CD69 expression were found on CD4+ or CD8+ T-cells at 1H. CONCLUSION: The increased activation of CD4+ T-cells after exercise might be due to a greater proportion of KLRG1+ cells in blood with a heightened state of activation. In contrast, exercise appears to inhibit the ability of KLRG1+ but not KLRG1- CD8+ T-cells to become activated. As KLRG1+ T-cells are incapable of proliferation, the possibility that exercise impacts on their effector capabilities remains to be determined.

The clonal expansion of T-lymphocytes in response to an antigenic stimulus is an essential process of adaptive immunity. Chromosome telomeres become progressively eroded with each round of cell division, eventually leading to replicative senescence. T-lymphocytes with a senescent phenotype are known to accumulate with age, increasing infection risk in middle-aged and elderly individuals. A sedentary lifestyle is associated with shortened telomeres in peripheral blood leukocytes, but the influence of regular exercise on the frequency of T-cells with a senescent phenotype in young and older adults is not known. PURPOSE: To examine the impact of estimated VO2max on the frequency of senescent blood T-cells in young and middle-aged men. METHODS: Twenty young (Y; age: 23.4 ± 3; BMI: 24.6 ± 3) and 20 middle-aged (O; age: 54 ± 3.6; BMI: 26.4 ± 3.4) healthy males provided a fasted resting blood sample, completed an assessment of percentage body fat and a physical activity status questionnaire designed to estimate VO2max. Y and O subjects were then divided into Hi and Lo VO2max groups (VO2max; Y: 51.2 ± 4.4 vs 42.6 ± 2.2 ml·kg-1·min-1; O: 38.7 ± 3.3 vs 29.5 ± 1.3 ml·kg-1·min-1) with n=10 in each group. Isolated lymphocytes were assessed for cell surface expression of senescence (KLRG1+, CD28-, CD57+), naïve (CD45RA+) and memory (CD45RO+) T-cell markers on CD3+ T-cells, CD4+ T-cells and CD8+ T-cells using four-colour flow cytometry. Differences in T-cell phenotype among the 4-groups was analysed by one-way ANOVA. RESULTS: O had a greater proportion of KLRG1+, CD57+, CD28, KLRG1+/CD57+ and CD45RA-/CD45RO+ CD8+ T-cells than Y, regardless of estimated VO2max. No differences in senescent phenotypes were found between the Hi and Lo VO2max groups in Y. In contrast, the Hi VO2max group in O had a significantly lower frequency of CD4+ and CD8+ T-cells expressing KLRG1+ (CD4: 58%; CD8: 23% less), CD57+ (CD4: 71%; CD8: 20% less), CD28- (CD4: 91%; CD8: 24% less), KLRG1+/CD57+ (CD4: 89%; CD8: 26% less) and CD45RA-/CD45RO+ (CD4: 20% less), in comparison to the Lo VO2max group in O. CONCLUSION: A higher estimated VO2max is associated with a lowered frequency of senescent and memory CD4+ and CD8+ T-cells in middle-aged but not younger men. These findings highlight the beneficial effects of regular physical activity on cellular immunity during ageing.

Monocytes are a heterogeneous group of cells, the relative distribution of which change in peripheral blood following a strenuous bout of aerobic exercise. Monocyte subtypes can be identified in blood based on the cell surface expression of CD14 and CD16: classic (CD14++bright/CD16−negative) and the CD16+dim (CD14++bright/CD16+dim) and CD16++bright (CD14+dim/CD16++bright) pro-inflammatory subtypes. Whole monocyte population changes in TLR2, TLR4 and HLA.DR expression have previously been documented after acute exercise without accounting for relative changes in monocyte subpopulations, therefore, this study examined their expression on classic and pro-inflammatory monocyte subsets following 45 min of treadmill running at 75% V˙O2max. Mononuclear cells isolated from the peripheral blood of moderately trained male subjects (n = 15) before (PRE), immediately after (POST) and 1 h after (1H) exercise were assessed for TLR2, TLR4 and HLA.DR expression on blood monocytes and their subpopulations using three-colour flow cytometry. Compared to PRE, the proportion of CD14+/CD16+ monocytes was 27% greater POST and 49% less at 1H and was associated with changes in the CD16++bright pro-inflammatory subtype (p < 0.05). TLR2 expression was 12% lower on CD16+dim monocytes POST (p < 0.05), whereas TLR4 and HLA.DR expression on total monocytes was 12% and 22% lower at 1H, respectively, and was attributed to changes in the classic (p < 0.05) and not the pro-inflammatory subsets (p > 0.05). We conclude that acute exercise causes localised changes in TLR2, TLR4 and HLA.DR expression within specific blood monocyte subpopulations, and could therefore be occurring at the cellular level. Such alterations might have significant implications for modulation of post-exercise immune surveillance.

BACKGROUND: The clonal expansion of T-lymphocytes in response to an antigenic stimulus is an essential process of adaptive immunity. Chromosome telomeres become progressively eroded with each round of cell division, eventually leading to replicative senescence (1). T-lymphocytes with a senescent phenotype are known to accumulate with age, increasing infection risk in middle-aged and elderly individuals (2). A sedentary lifestyle is associated with shortened telomeres in peripheral blood leukocytes, but the influence of regular exercise on the frequency of T-cells with a senescent phenotype in young and older adults is not known.

It is well-known that athletes are at an increased susceptibility to illness when adhering to arduous training regimens in preparation for endurance events. Senescent T-lymphocytes are antigen-experienced cells that accumulate with age and fail to clonally expand following further antigenic stimulation, thus predisposing the individual to a greater risk of infection. Although acute exercise is known to alter the frequency of senescent T-cells in blood, less is known about the effects of long-term endurance training. PURPOSE: To examine the effects of 6-months training preparation for an Ironman triathlon on the frequency of senescent blood T-cells. METHODS: Ten club-level triathletes (9 males; 1 female: Age: 42.9 ± 3.1 yrs) provided a fasted resting blood sample in the morning at 27 (DEC), 21 (JAN), 15 (MAR), 9 (MAY) and 3 (JUN) weeks before the 2008 Zurich Ironman Triathlon. An additional sample was collected 2-weeks post-competition (AUG). Total training hours completed by the participants over the 6-month period was 284.4 ± 122.9. Isolated blood lymphocytes were labelled with monoclonal antibodies to assess cell surface expression and co-expression of the T-cell senescence markers KLRG1, CD57 and CD28; and the naïve and memory T-cell markers CD45RA and CD45RO on CD3+, CD3+/CD4+ and CD3+/CD8+ T-cells using four-colour flow cytometry. Data was analyzed for time-change using a repeated measures linear mixed model. RESULTS: Compared to DEC, the percentage of CD4+ T-cells expressing KLRG1 increased by 71% (MAR), 20% (MAY) and 71% (AUG). CD4+ T-cells co-expressing KLRG1 and CD57 was 192% greater in AUG compared to DEC. No changes in senescent markers were found on CD8+ T-cells. The proportion of transitional T-cells (CD45RA+/CD45RO+) increased from MAY to JUN by 141% and 115% for CD4+ and CD8+ T-cells respectively. The proportion of memory CD8+ T-cells (CD45RA-/CD45RO+) was 40% (MAY) and 55% (AUG) greater than DEC. CONCLUSION: Adherence to a 6-month training program in preparation for an Ironman triathlon leads to an increased frequency of senescent CD4+ T-cells (KLRG1+/CD57+) and a greater proportion of naïve to memory transitional CD4+ and CD8+ T-cells in blood. These changes could have important implications for athlete infection risk during periods of arduous training.

Senescent T-lymphocytes are antigen-experienced cells that express the killer-cell lectin-like receptor G1 (KLRG1) and/or CD57; fail to clonally expand following further antigenic stimulation and prevail in the resting blood of older adults compared to the young. Physical exercise mobilises T-lymphocytes into the bloodstream and is therefore a model with which to compare age-related phenotypes of blood-resident T-cells with those T-cells entering the blood from peripheral lymphoid compartments. Eight young (Y; Age: 21±3 years) and 8 older (O; Age: 56±3 years) healthy males completed a maximal treadmill exercise protocol. Blood lymphocytes isolated before, immediately after and 1h after exercise were assessed for cell surface expression of KLRG1, CD57, CD28, CD45RA, CD45RO, CD62L and lymphocyte subset markers using three-colour flow cytometry. Lymphocyte subset numbers (CD3+, CD3+/CD4+, CD3+/CD8 and CD3−/CD56+) increased with exercise (p<0.05) but were not different between Y and O. At rest and immediately after exercise, the percentage of CD3+/CD8+ T-lymphocytes expressing KLRG1 and CD45RO was greater in O than Y, whereas Y had a greater expression of CD45RA and CD62L than O. The percentage of all CD3+/CD8+ and CD3+/CD4+ T-lymphocytes expressing KLRG1 and CD57 increased after exercise, but the magnitude of change was not age-dependent. In conclusion, there is a greater proportion of senescent CD3+/CD8+ T-lymphocytes in the blood of older adults compared to young at rest and immediately after exhaustive exercise, indicating that the greater frequency of KLRG1+/CD8+ T-lymphocytes in older humans is ubiquitous and not localised to the peripheral blood.

This study investigated the uptake, kinetics and cellular distribution of different surface coated quantum dots (QDs) before relating this to their toxicity. J774.A1 cells were treated with organic, COOH and NH2 (PEG) surface coated QDs (40 nM). Model 20 nm and 200 nm COOH-modified coated polystyrene beads (PBs) were also examined (50 microg ml(-1)). The potential for uptake of QDs was examined by both fixed and live cell confocal microscopy as well as by flow cytometry over 2 h. Both the COOH 20 nm and 200 nm PBs were clearly and rapidly taken up by the J774.A1 cells, with uptake of 20 nm PBs being relatively quicker and more extensive. Similarly, COOH QDs were clearly taken up by the macrophages. Uptake of NH2 (PEG) QDs was not detectable by live cell imaging however, was observed following 3D reconstruction of fixed cells, as well as by flow cytometry. Cells treated with organic QDs, monitored by live cell imaging, showed only a small amount of uptake in a relatively small number of cells. This uptake was insufficient to be detected by flow cytometry. Imaging of fixed cells was not possible due to a loss in cell integrity related to cytotoxicity. A significant reduction (p<0.05) in the fluorescent intensity in a cell-free environment was found with organic QDs, NH2 (PEG) QDs, 20 nm and 200 nm PBs at pH 4.0 (indicative of an endosome) after 2 h, suggesting reduced stability. No evidence of exocytosis was found over 2 h. These findings confirm that surface coating has a significant influence on the mode of NP interaction with cells, as well as the subsequent consequences of that interaction.

Clonal expansion of T lymphocytes in response to antigenic stimulation is a fundamental process of adaptive immunity. As a consequence of clonal expansion, some T lymphocytes acquire a senescent phenotype, fail to replicate in response to further antigenic stimulation, and express the killer cell lectin-like receptor G1 (KLRG1) and/or CD57. Physical exercise elicits a mobilization of large numbers of T lymphocytes into the bloodstream from peripheral lymphoid compartments, but the frequency of senescent cells in the mobilized population is not known. Eight male runners (age: 29 +/- 9 yr; maximal O2 uptake 62 +/- 6 ml x kg(-1) x min(-1)) performed an intensive treadmill-running protocol at 80% maximal O2 uptake to volitional exhaustion. Blood lymphocytes isolated before, immediately after, and 1 h after exercise were assessed for cell surface expression of KLRG1, CD57, CD28, CD45RA, CD45RO, CD62L, and lymphocyte subset markers (CD3, CD4, CD8, CD56) by flow cytometry. The percentage of all CD3+ T lymphocytes expressing KLRG1 and CD57 increased with exercise (P < 0.01). The change in T-lymphocyte KLRG1 expression was attributed to both CD4+ and CD8 bright T cells, with the relative change being greater for the CD8 bright population (P < 0.01). Mobilized T-lymphocyte populations expressing KLRG1 and CD57 appeared to extravasate the peripheral blood compartment after 1 h of recovery. In conclusion, T lymphocytes with a senescent phenotype are mobilized and subsequently removed from the bloodstream in response to acute high-intensity exercise. This suggests that T lymphocytes contained within the peripheral lymphoid compartments that are mobilized by exercise are likely to be at a more advanced stage of biological aging and have a reduced capacity for clonal expansion than blood-resident T cells.

The lymphocytopenia that occurs during the recovery stage of exercise may be a result of apoptosis through an increased expression of CD95, a loss of the complement regulatory proteins CD55 and CD59, or both. Trained subjects completed intensive, moderate, and downhill treadmill-running protocols. Blood lymphocytes isolated before, immediately after, 1h after, and 24h after each exercise test were assessed for markers of apoptosis (Annexin-V(+), HSP60(+)), and CD55, CD59, and CD95 expression by flow cytometry. Lymphocytopenia occurred 1h after intensive and downhill running exercise, but no changes in the percentage of Annexin-V + or HSP60 + lymphocytes were found. Numbers of CD95(+), CD55(dim), and CD59(dim) lymphocytes increased immediately after intensive and downhill exercise, which were attributed to the selective mobilization and subsequent efflux of CD8(+) and CD56(+) lymphocyte subsets. No differences were found between the intensive and downhill protocols. In conclusion, apoptosis of circulating lymphocytes does not appear to contribute to exercise-induced lymphocytopenia.

T-cell senescence occurs during aging as a consequence of chromosome telomere shortening in response to repetitive antigenic stimulation. Senescent T-lymphocytes normally exhibit a “memory” phenotype (i.e. CD62L-/CD45RA-/CD45RO+) and express CD57 and the killer-cell lectin-like receptor G1 (KLRG1) on the cell surface. Physical exercise elicits a mobilisation of senescent T-lymphocytes into the bloodstream in young subjects (Simpson et al., Immunology, 116, 68. 2005), but it is not known if this also occurs in older adults. PURPOSE: To determine the frequency of senescent T-lymphocytes in the blood compartment after an acute bout of high-intensity exercise in young (Y) and old (O) subjects. METHODS: Eight Y (Age: 21 ± 3 yrs) and 8 O (Age: 56 ± 3 yrs) healthy males completed a maximal treadmill walking protocol. Blood lymphocytes isolated before, immediately after and 1h after exercise were assessed for cell surface expression of KLRG1, CD57, CD28, CD45RA, CD45RO, CD62L and lymphocyte subset markers using four-colour flow cytometry. RESULTS: The numbers of CD3+, CD3+/CD4+, CD3+/CD8+ T-lymphocytes and CD3-/CD56+ NK-cells increased with exercise (p<0.05) but were not different between Y and O (P>0.05). At rest and immediately after exercise, the percentage of all CD3+/CD8+ T-lymphocytes expressing KLRG1, CD57 and CD45RO was greater in O than Y, whereas Y had a greater expression of CD28, CD45RA and CD62L than O (p<0.05). CD3+/CD4+ T-lymphocytes in O had a greater expression of CD45RO and a reduced expression of CD45RA in comparison to Y before and after exercise. The percentage of all CD3+/CD8+ and CD3+/CD4+ T-lymphocytes expressing KLRG1 and CD57 increased in both Y and O in response to exercise, but the magnitude of change was not different between Y and O. No changes in the percentage of all CD3-/CD56+ NK-cells expressing these cell-surface receptors occurred in response to exercise (p>0.05). CONCLUSIONS: Older adults have a greater percentage of senescent CD3+/CD8+ T-lymphocytes in blood than their younger counterparts both at rest and after an acute bout of high-intensity exercise. Exercise elicits a mobilisation of senescent T-lymphocytes into the blood compartment in both Y and O subjects, suggesting that T-cells mobilised by exercise have a reduced capacity for clonal expansion than blood resident T-cells.

Exercise is known to result in the haemolysis of red blood cells (RBCs). Although mechanical stressors such as footstrike and an increased velocity of blood flow may be involved, the biological mechanisms that underpin RBC haemolysis remain elusive. RBCs are potentially susceptible to lysis by autologous complement activation. RBCs are protected from the lytic effects of complement by regulatory proteins (CRPs) bound to the cell membrane via glycosylphosphatidylinositol (GPI) anchors. This study aimed to determine if marathon running would result in RBC haemolysis through a loss of membrane expression of the CRPs CD55 (decay accelerating factor) and CD59 (membrane attack complex inhibitory factor). Blood samples were obtained from 14 male runners before, within 30 min after, and 24 h after completion of the 2004 London Marathon. RBCs were assessed for cell surface CD55 and CD59 expression using indirect immunofluorescence assays and flow cytometry. No significant changes in the total RBC count, haematocrit or haemoglobin concentrations were found in response to running the marathon ( P > 0.05). Blood bilirubin concentrations after the marathon were significantly greater than the pre-race values ( P < 0.01). The relative fluorescent intensity (arbitrary units) of CD55 and CD59 expression on RBC membranes did not change in response to the marathon race ( P > 0.05). In conclusion, marathon running did not alter the expression of CD55 or CD59 on RBCs, despite concomitant elevations in blood bilirubin concentrations. Consequently, any haemolysis of RBCs that occurred in response to the marathon was not likely due to a loss of membrane bound CRPs and subsequent cell lysis by autologous complement.

This study examined the effects of intensive, moderate and downhill treadmill running on blood lymphocyte expression of adhesion/activation (AA) molecules. Trained subjects completed three treadmill-running protocols of identical duration: (1) an intensive protocol at 80% \( \ifmmode\expandafter\dot\else\expandafter\.\fi{V}_{{{\text{O}}_{{2\max }} }} \) to volitional exhaustion, (2) a moderate protocol at 60% \( \ifmmode\expandafter\dot\else\expandafter\.\fi{V}_{{{\text{O}}_{{2\max }} }} \) and (3) a −10% downhill (eccentric) protocol at 80% \( \ifmmode\expandafter\dot\else\expandafter\.\fi{V}_{{{\text{O}}_{{2\max }} }} \). Blood samples were taken before, immediately after, 1 and 24 h after exercise. Isolated lymphocytes were assessed for expression of the AA molecules CD54, CD18 and CD53 by flow cytometry. Lymphocyte counts increased immediately after all running protocols. Lymphocytopenia was observed 1 h after the intensive and eccentric protocols only. Plasma creatine kinase increased 24 h after the downhill protocol only. Increases in the number and percentage of CD54+, CD18bright and CD53bright lymphocytes were observed immediately after the intensive and eccentric protocols, with the numbers falling below pre-exercise values at 1 h post-exercise for all protocols. No differences were found between the intensive protocol and the eccentric protocol at the same relative intensity. Analysis of lymphocyte subsets showed that the total number of CD3+, CD4+, CD8+ and CD56+ lymphocytes increased after the intensive protocol before falling below pre-exercise values at 1 h post-exercise. A relatively greater mobilisation of CD56+ and CD8+ cells accounts for the changes in CD54+, CD18bright and CD53bright cell populations. Lymphocytes that enter and exit the circulation following exercise express high levels of AA molecules, which may mediate extravasation and post-exercise lymphocytopenia. This effect appears to be influenced by exercise intensity and not muscle damage.

We have previously shown that a single bout of exercise elicits a preferential mobilisation and subsequent extravasation of blood lymphocyte subsets expressing high levels of adhesion/activation (AA) molecules and low levels of complement regulatory proteins (Simpson et al. Med. Sci. Sports Exerc. 37, S336, 2005). Repeated bouts of exercise have the potential to accumulatively alter the trafficking of lymphocyte subset populations in the blood compartment. PURPOSE: To examine the effects of repeated bouts of mountainous hill-running on: blood lymphocyte subset counts; lymphocyte cell surface expression of glycoproteins; and plasma concentrations of TNFα and the acute phase proteins CRP, α-1-ACT, fibrinogen, fibronectin and haptoglobin. METHODS: Seven trained males (Age: 28±4yrs,: VO2max: 64 ± 3 ml·kg·mn−1) completed four bouts of hill-running on four consecutive days. Each bout consisted of 1126m ascent/descent over a distance of 24.5km and took 2–2.5h to complete. Blood samples were collected before, immediately after, 1h after completion and 24h after the start of each bout. Isolated lymphocytes were assessed for cell surface expression of subset markers (CD3, CD4, CD8, CD56), AA molecules (CD18, CD53, CD54), complement regulatory proteins (CD55, CD59) and the cell surface death receptor CD95 by flow cytometry. RESULTS: No statistical differences in run time or heart rate were found among the four exercise bouts. For all bouts, total lymphocyte counts and lymphocyte subset counts did not change immediately after exercise. At 1h post-exercise, CD3+, CD4+, CD8+ and CD56+ lymphocytes and the CD3+, CD8+ and CD56+ lymphocytes expressing CD18bright, CD53bright, CD54+, CD55dim, CD59dim and CD95 fell below the pre-exercise value after the first two bouts only. Lymphocyte subset counts and phenotypes returned to the pre-exercise values 24h after all bouts. Plasma CRP concentrations increased 24h after the first bout and remained elevated throughout the subsequent bouts. No changes in plasma concentrations of TNF? or the other acute phase proteins were found. CONCLUSION: Four consecutive days of hill-running elicited marked reductions in the number of lymphocyte subset populations expressing high levels of AA molecules and low levels of complement regulatory proteins. This effect occurred only after the first two exercise bouts, suggesting that a possible “carry-over” effect on lymphocyte trafficking during the subsequent exercise bouts occurred. Basal lymphocyte counts and phenotype characteristics, however, appeared to be restored in the blood compartment after 24h of recovery despite sustained elevations in plasma CRP activity.

Exercise elicits an initial increase in the number of blood lymphocytes, followed by a rapid lymphocytopenia in the recovery phase. Alterations in cell phenotype accompany changes in lymphocyte number. The mechanisms underlying these changes and their potential functional consequences are not understood. PURPOSE To examine the effects of intensive, moderate and eccentric exercise on lymphocyte apoptosis, and lymphocyte expression of the complement regulatory proteins CD55 (DAF) and CD59 (MACIF), and the adhesion/activation molecules CD18 (β2 integrin), CD53 and CD54 (ICAM-1). METHODS Eight trained males (Age: 28 ± 5 yrs,: VO2max 63 ± 3 ml-kg·min−1) completed three treadmill running protocols: (1) an intensive protocol at 80% VO2max, (2) a moderate protocol at 60% VO2max, and (3) a −10% eccentric protocol at 80% VO2max. Blood samples were taken before exercise, immediately after, 1h and 24h later. Isolated lymphocytes were assessed for markers of apoptosis (Annexin-V, HSP60 and CD95) and expression of CD proteins using flow cytometry. RESULTS No lymphocyte apoptosis was found after any of the running protocols. Using CD55, CD59, CD18 and CD53 monoclonal antibodies, two populations of lymphocytes with strikingly different fluorescent intensities (“dim” or “bright”) were found. Together these accounted for >98% of lymphocytes. An increase in the percentage of CD55dim, CD59dim, CD18bright, CD53bright and CD54+ cells occurred immediately after the intensive protocol, before falling below baseline at 1h post-exercise (p<0.05). The phenotypes of lymphocytes at 24hr closely resembled those found pre-exercise. The eccentric protocol at the same relative intensity produced similar results. No significant changes in lymphocyte phenotype were observed following the moderate protocol (p>0.05). Two-colour analysis of lymphocyte subsets showed that increases in CD8+ T-lymphocytes and CD3−/CD56+ Natural Killer (NK) cells immediately after the intensive protocol, and their subsequent fall within 1 hr account for the changes in CD55dim, CD59dim, CD18bright CD53bright and CD54+ populations. No changes in CD4+ T-lymphocytes were found. CONCLUSION Apoptosis affecting blood lymphocytes does not contribute to post-exercise lymphocytopenia. Intensive treadmill running results in the appearance in the blood of additional CD8+ T lymphocytes and CD3−/CD56+NK cells. Lymphocytes expressing high levels of cell surface adhesion/activation molecules appear to exit the blood within 1h post exercise. The basis of selection of lymphocyte subsets for recruitment into the blood, and their fate after exercise-induced extravasation requires investigation.