Success of long duration space missions will depend upon robust immunity. Decreased immunity has ... more Success of long duration space missions will depend upon robust immunity. Decreased immunity has been observed in astronauts during short duration missions, as evident by the reactivation of latent herpes viruses. Seventeen astronauts were studied for reactivation and shedding of latent herpes viruses before, during, and after 9-14 days of 8 spaceflights. Blood, urine, and saliva samples were collected 10 days before the flight (L-10), during the flight (saliva only), 2-3h after landing (R+0), 3 days after landing (R+3), and 120 days after landing (R+120). Values at R+120 were used as baseline levels. No shedding of viruses occurred before flight, but 9 of the 17 (designated "virus shedders") shed at least one or more viruses during and after flight. The remaining 8 astronauts did not shed any of the 3 target viruses (non-virus shedders). Virus-shedders showed elevations in 10 plasma cytokines (IL-1α, IL-6, IL-8, IFNγ, IL-4, IL-10, IL-12, IL-13, eotaxin, and IP-10) at R+0 over baseline values. Only IL-4 and IP-10 were elevated in plasma of non-virus shedders. In virus shedders, plasma IL-4 (a Th2 cytokine) was elevated 21-fold at R+0, whereas IFNγ (a Th1 cytokine) was elevated only 2-fold indicating a Th2 shift. The inflammatory cytokine IL-6 was elevated 33-fold at R+0. In non-shedding astronauts at R+0, only IL-4 and IP-10 levels were elevated over baseline values. Elevated cytokines began returning to normal by R+3, and by R+120 all except IL-4 had returned to baseline values. These data show an association between elevated plasma cytokines and increased viral reactivation in astronauts.
Acute exercise alters the surface expression of toll-like receptors (TLRs) and HLA.DR on blood mo... more Acute exercise alters the surface expression of toll-like receptors (TLRs) and HLA.DR on blood monocytes, which could transiently compromise immunity. As serum factors might be responsible, we examined the effects of autologous post-exercise serum exposure on TLR2, TLR4 and HLA.DR expression on resting blood monocytes and their subtypes. Eight trained cyclists completed an ergometer 60 km time trial. PBMCs and serum were obtained before, immediately after and 1 h after exercise. TLR2, TLR4 or HLA.DR expression (gMFI) was determined on blood monocyte subtypes expressing combinations of CD14 and CD16 by flow cytometry, and on resting monocytes exposed to 50% autologous serum (pre, immediately after or 1 h after exercise) for 18 h in culture. Immediately after exercise, total monocyte expression of TLR2 and TLR4 increased by 41 and 27%, respectively, while HLA.DR expression was 39% lower than baseline. TLR2 and TLR4 was 53 and 84% greater 1 h after exercise, respectively, while HLA.DR was 48% lower. Changes in TLR2 and TLR4 expression occurred on the CD14++bright/CD16+dim monocyte subtype only, while HLA.DR expression changed on the CD14+dim/CD16++bright subtype. Serum did not affect monocyte TLR2 or TLR4 expression but 1 h post serum increased expression of HLA.DR on total monocytes and the CD14+dim/CD16++bright subtype, which was in contrast to the change observed at this time after exercise. We conclude that a bout of strenuous aerobic exercise alters the surface expression of TLR2, TLR4 and HLA.DR on blood monocytes and some of their subtypes, but these changes appear to be unrelated to blood serum factors.
The lymphocytopenia that occurs during the recovery stage of exercise may be a result of apoptosi... more 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+, CD55dim, and CD59dim 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.
Athletes appear to be at a greater risk of illness while undertaking arduous training regimens in... more Athletes appear to be at a greater risk of illness while undertaking arduous training regimens in preparation for endurance events. As infection susceptibility has been linked with increased proportions of differentiated and senescent T cells in the periphery, changes in the proportions of these cell types due to long-term high-volume exercise training could have important implications for athlete infection risk. This study examined the effects of 6-month training preparation for an Ironman triathlon on the proportions of naïve, memory and senescent T cells in resting blood. Ten club-level triathletes (9 males; 1 female: 43 ± 3 years) were sampled at 27 (December), 21 (January), 15 (March), 9 (May) and 3 (June) weeks before an Ironman Triathlon. An additional sample was collected 2-week post-competition (August). Four-colour flow cytometry was used for the phenotypic analysis of CD4+ and CD8+ blood T cells. Proportions of differentiated (KLRG1+/CD57−) CD8+ T cells and “transitional” (CD45RA+/CD45RO+) CD4+ and CD8+ T cells increased with training, as the values in June were elevated 37, 142 and 116%, respectively, from those observed in December. Proportions of senescent (KLRG1+/CD57+) CD4+ or CD8+ T cells did not change during the training phase. Two weeks post-race, proportions of differentiated CD8+ T cells had returned to baseline values, while the proportions of senescent CD4+ T cells increased 192% alongside a 31% reduction in naïve (CD45RA+/CD45RO−) cells. In conclusion, increases in differentiated and “transitional” T cells due to arduous exercise training could compromise host protection to novel pathogens and increase athlete infection risk, although whether or not the composition of naïve and differentiated T cells in blood can serve as prognostic biomarkers in athletes remains to be established.
Cytotoxic T-lymphocytes co-express the T-cell receptor, CD3 and the MHC I restricted antigen CD8.... more Cytotoxic T-lymphocytes co-express the T-cell receptor, CD3 and the MHC I restricted antigen CD8. Although total CD8 expression is often used to identify CD8(+) T-cells in blood, errors are associated with this method as some CD3 negative natural killer (NK)-cells are known to express CD8. As greater relative proportions of NK-cells are found in the blood compartment after exercise, these errors are likely to be amplified in post exercise blood samples. To test this, isolated blood lymphocytes obtained from aerobically trained male subjects before, immediately after and 1h after an exhaustive treadmill-running protocol were surface stained for CD3, CD4, CD8, CD16, and CD56 and analysed by multi-colour flow cytometry. It was found that 25.4+/-16.9% of all CD8(+) cells at rest were CD3 negative, CD8(dim+) and expressed the NK-cell markers CD16 and CD56. The magnitude of this error increased to 40.8+/-20.7% immediately after exercise due to an influx of CD8(dim+) NK-cells. Although all CD8(bright+) cells expressed CD3, gating around the CD8(bright+) cells only identified 79.2+/-8.7% of the total CD3(+)/CD8(+) T-cell population; however, the magnitude of this error did not change after exercise despite the altered proportions of CD8(bright+) and CD8(dim+) cells. In conclusion, total lymphocyte expression of CD8 should not be used as a single antigenic marker to identify CD8(+) T-cells after an acute bout of exercise. Although there are errors associated with using CD8(bright+) as a single antigenic marker to identify CD3(+) T-cells, these are not amplified in response to exercise.
Exercise is known to result in the haemolysis of red blood cells (RBCs). Although mechanical stre... more 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 ly... more 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.
Purpose This study compared the acute immune response, inflammation, and lipid peroxidation to a ... more Purpose This study compared the acute immune response, inflammation, and lipid peroxidation to a 75 km cycling time trial in male athletes testing positive or negative for latent cytomegalovirus (CMV) infection. Design Trained cyclists (N = 20) were tested for CMV serostatus, and cycled 75 km on a mountainous course using indoor trainers with continuous workload monitoring. Pre-, post-, and 1 h post-exercise blood samples were analyzed for total blood leukocyte counts, blood granulocyte (GR) and monocyte (MO) phagocytosis (PHAG) and oxidative burst activity (OBA), four plasma cytokines, and plasma F2-isoprostanes. Results Forty percent of the subjects tested positive for CMV. No differences in subject characteristics were found between CMVpos and CMVneg groups. Mean power (57.3 ± 1.6, 59.4 ± 1.8 % maximal Watts, p = 0.803), heart rate (87.0 ± 1.0, 86.5 ± 1.3 % maximal heart rate, p = 0.376), and total time (2.56 ± 0.08, 2.60 ± 0.08 h, p = 0.744) to complete the 75 km cycling time trial did not differ between CMVpos and CMVneg groups. Whereas exercise induced significant changes in total blood leukocyte counts, GR and MO-PHAG, four plasma cytokines, and plasma F2-isoprostanes (p < 0.05, ω2 > 0.03), these exercise-induced changes did not differ between CMVpos and CMVneg groups (p > 0.05, ω2 < 0.01). Conclusions CMV serostatus does not appear to influence these innate immune responses or markers of inflammation and lipid peroxidation in response to a single bout of heavy exertion.
Canadian journal of applied physiology = Revue canadienne de physiologie appliquée, 2005
Hill races usually include large downhill running sections, which can induce significant degrees ... more Hill races usually include large downhill running sections, which can induce significant degrees of muscle damage in a field setting. This study examined the link between muscle damage, oxidative stress, and immune perturbations following a 7-km mountainous hill race with 457 m of ascent and 457 m of descent. Venous blood samples were taken from 7 club level runners before, immediately after, and 48 hrs postrace. Samples were analysed for total and differential leukocyte counts, markers of muscle damage (CK), lipid peroxidation (MDA), and acute phase proteins (CRP; fibrinogen; alpha-1-ACT). The total antioxidant status (TEAC) and plasma levels of the proinflammatory cytokines IL-6, IL-8, and TNF-alpha were also determined. Subjective pain reports, and plasma activities of CK, MDA, and circulatory monocytes reached peak values at 48 hrs postrace (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). TEAC and the cytokine IL-8 increased immediately after the race (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). Plasma TNF-alpha remained unchanged (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.05). Despite the reports of muscle damage and soreness, no evidence of an acute phase response was observed (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.05), which may be explained by the failure of the race to induce a plasma TNF-alpha response. Future studies should examine the link between muscle damage, oxidative stress, and the acute phase response following hill races of longer duration with larger eccentric components.
The aim of this study was to compare selected physiological variables and performance markers of ... more The aim of this study was to compare selected physiological variables and performance markers of soldiers from two “elite” units of the British Army. Ten soldiers from each of the two units were recruited for this study (n = 20). All participants completed three tests while carrying a 20 kg backpack load: (1) a maximal treadmill test using the Bruce protocol; (2) a 2 mile backpack run test specific to Unit A on a consistently flat tarmac road; and (3) a 29 km time-trial over hilly terrain typical of a mountainous area used by Unit B for performance assessment. Heart rate, maximal blood lactate concentration and performance (run time) were assessed during all three tests, with peak oxygen uptake also being measured during the maximal treadmill test. Measurements of anthropometry, isokinetic strength and mental toughness (MT48) were also recorded. There were no significant differences in terms of performance markers between the units (P > 0.05). Performance on the maximal treadmill test correlated with performance on the 2 mile backpack run test (r = −0.57) and 29 km time-trial (r = −0.66). Performance on the 2 mile backpack run test in turn correlated with 29 km time-trial performance (r = −0.77), accounting for 59% of the variance. In conclusion, the maximal treadmill test and the 2 mile backpack run test are useful indicators of performance on the arduous hill march and could be employed in the screening and selection of potential recruits.
Success of long duration space missions will depend upon robust immunity. Decreased immunity has ... more Success of long duration space missions will depend upon robust immunity. Decreased immunity has been observed in astronauts during short duration missions, as evident by the reactivation of latent herpes viruses. Seventeen astronauts were studied for reactivation and shedding of latent herpes viruses before, during, and after 9-14 days of 8 spaceflights. Blood, urine, and saliva samples were collected 10 days before the flight (L-10), during the flight (saliva only), 2-3h after landing (R+0), 3 days after landing (R+3), and 120 days after landing (R+120). Values at R+120 were used as baseline levels. No shedding of viruses occurred before flight, but 9 of the 17 (designated &quot;virus shedders&quot;) shed at least one or more viruses during and after flight. The remaining 8 astronauts did not shed any of the 3 target viruses (non-virus shedders). Virus-shedders showed elevations in 10 plasma cytokines (IL-1α, IL-6, IL-8, IFNγ, IL-4, IL-10, IL-12, IL-13, eotaxin, and IP-10) at R+0 over baseline values. Only IL-4 and IP-10 were elevated in plasma of non-virus shedders. In virus shedders, plasma IL-4 (a Th2 cytokine) was elevated 21-fold at R+0, whereas IFNγ (a Th1 cytokine) was elevated only 2-fold indicating a Th2 shift. The inflammatory cytokine IL-6 was elevated 33-fold at R+0. In non-shedding astronauts at R+0, only IL-4 and IP-10 levels were elevated over baseline values. Elevated cytokines began returning to normal by R+3, and by R+120 all except IL-4 had returned to baseline values. These data show an association between elevated plasma cytokines and increased viral reactivation in astronauts.
Acute exercise alters the surface expression of toll-like receptors (TLRs) and HLA.DR on blood mo... more Acute exercise alters the surface expression of toll-like receptors (TLRs) and HLA.DR on blood monocytes, which could transiently compromise immunity. As serum factors might be responsible, we examined the effects of autologous post-exercise serum exposure on TLR2, TLR4 and HLA.DR expression on resting blood monocytes and their subtypes. Eight trained cyclists completed an ergometer 60 km time trial. PBMCs and serum were obtained before, immediately after and 1 h after exercise. TLR2, TLR4 or HLA.DR expression (gMFI) was determined on blood monocyte subtypes expressing combinations of CD14 and CD16 by flow cytometry, and on resting monocytes exposed to 50% autologous serum (pre, immediately after or 1 h after exercise) for 18 h in culture. Immediately after exercise, total monocyte expression of TLR2 and TLR4 increased by 41 and 27%, respectively, while HLA.DR expression was 39% lower than baseline. TLR2 and TLR4 was 53 and 84% greater 1 h after exercise, respectively, while HLA.DR was 48% lower. Changes in TLR2 and TLR4 expression occurred on the CD14++bright/CD16+dim monocyte subtype only, while HLA.DR expression changed on the CD14+dim/CD16++bright subtype. Serum did not affect monocyte TLR2 or TLR4 expression but 1 h post serum increased expression of HLA.DR on total monocytes and the CD14+dim/CD16++bright subtype, which was in contrast to the change observed at this time after exercise. We conclude that a bout of strenuous aerobic exercise alters the surface expression of TLR2, TLR4 and HLA.DR on blood monocytes and some of their subtypes, but these changes appear to be unrelated to blood serum factors.
The lymphocytopenia that occurs during the recovery stage of exercise may be a result of apoptosi... more 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+, CD55dim, and CD59dim 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.
Athletes appear to be at a greater risk of illness while undertaking arduous training regimens in... more Athletes appear to be at a greater risk of illness while undertaking arduous training regimens in preparation for endurance events. As infection susceptibility has been linked with increased proportions of differentiated and senescent T cells in the periphery, changes in the proportions of these cell types due to long-term high-volume exercise training could have important implications for athlete infection risk. This study examined the effects of 6-month training preparation for an Ironman triathlon on the proportions of naïve, memory and senescent T cells in resting blood. Ten club-level triathletes (9 males; 1 female: 43 ± 3 years) were sampled at 27 (December), 21 (January), 15 (March), 9 (May) and 3 (June) weeks before an Ironman Triathlon. An additional sample was collected 2-week post-competition (August). Four-colour flow cytometry was used for the phenotypic analysis of CD4+ and CD8+ blood T cells. Proportions of differentiated (KLRG1+/CD57−) CD8+ T cells and “transitional” (CD45RA+/CD45RO+) CD4+ and CD8+ T cells increased with training, as the values in June were elevated 37, 142 and 116%, respectively, from those observed in December. Proportions of senescent (KLRG1+/CD57+) CD4+ or CD8+ T cells did not change during the training phase. Two weeks post-race, proportions of differentiated CD8+ T cells had returned to baseline values, while the proportions of senescent CD4+ T cells increased 192% alongside a 31% reduction in naïve (CD45RA+/CD45RO−) cells. In conclusion, increases in differentiated and “transitional” T cells due to arduous exercise training could compromise host protection to novel pathogens and increase athlete infection risk, although whether or not the composition of naïve and differentiated T cells in blood can serve as prognostic biomarkers in athletes remains to be established.
Cytotoxic T-lymphocytes co-express the T-cell receptor, CD3 and the MHC I restricted antigen CD8.... more Cytotoxic T-lymphocytes co-express the T-cell receptor, CD3 and the MHC I restricted antigen CD8. Although total CD8 expression is often used to identify CD8(+) T-cells in blood, errors are associated with this method as some CD3 negative natural killer (NK)-cells are known to express CD8. As greater relative proportions of NK-cells are found in the blood compartment after exercise, these errors are likely to be amplified in post exercise blood samples. To test this, isolated blood lymphocytes obtained from aerobically trained male subjects before, immediately after and 1h after an exhaustive treadmill-running protocol were surface stained for CD3, CD4, CD8, CD16, and CD56 and analysed by multi-colour flow cytometry. It was found that 25.4+/-16.9% of all CD8(+) cells at rest were CD3 negative, CD8(dim+) and expressed the NK-cell markers CD16 and CD56. The magnitude of this error increased to 40.8+/-20.7% immediately after exercise due to an influx of CD8(dim+) NK-cells. Although all CD8(bright+) cells expressed CD3, gating around the CD8(bright+) cells only identified 79.2+/-8.7% of the total CD3(+)/CD8(+) T-cell population; however, the magnitude of this error did not change after exercise despite the altered proportions of CD8(bright+) and CD8(dim+) cells. In conclusion, total lymphocyte expression of CD8 should not be used as a single antigenic marker to identify CD8(+) T-cells after an acute bout of exercise. Although there are errors associated with using CD8(bright+) as a single antigenic marker to identify CD3(+) T-cells, these are not amplified in response to exercise.
Exercise is known to result in the haemolysis of red blood cells (RBCs). Although mechanical stre... more 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 ly... more 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.
Purpose This study compared the acute immune response, inflammation, and lipid peroxidation to a ... more Purpose This study compared the acute immune response, inflammation, and lipid peroxidation to a 75 km cycling time trial in male athletes testing positive or negative for latent cytomegalovirus (CMV) infection. Design Trained cyclists (N = 20) were tested for CMV serostatus, and cycled 75 km on a mountainous course using indoor trainers with continuous workload monitoring. Pre-, post-, and 1 h post-exercise blood samples were analyzed for total blood leukocyte counts, blood granulocyte (GR) and monocyte (MO) phagocytosis (PHAG) and oxidative burst activity (OBA), four plasma cytokines, and plasma F2-isoprostanes. Results Forty percent of the subjects tested positive for CMV. No differences in subject characteristics were found between CMVpos and CMVneg groups. Mean power (57.3 ± 1.6, 59.4 ± 1.8 % maximal Watts, p = 0.803), heart rate (87.0 ± 1.0, 86.5 ± 1.3 % maximal heart rate, p = 0.376), and total time (2.56 ± 0.08, 2.60 ± 0.08 h, p = 0.744) to complete the 75 km cycling time trial did not differ between CMVpos and CMVneg groups. Whereas exercise induced significant changes in total blood leukocyte counts, GR and MO-PHAG, four plasma cytokines, and plasma F2-isoprostanes (p < 0.05, ω2 > 0.03), these exercise-induced changes did not differ between CMVpos and CMVneg groups (p > 0.05, ω2 < 0.01). Conclusions CMV serostatus does not appear to influence these innate immune responses or markers of inflammation and lipid peroxidation in response to a single bout of heavy exertion.
Canadian journal of applied physiology = Revue canadienne de physiologie appliquée, 2005
Hill races usually include large downhill running sections, which can induce significant degrees ... more Hill races usually include large downhill running sections, which can induce significant degrees of muscle damage in a field setting. This study examined the link between muscle damage, oxidative stress, and immune perturbations following a 7-km mountainous hill race with 457 m of ascent and 457 m of descent. Venous blood samples were taken from 7 club level runners before, immediately after, and 48 hrs postrace. Samples were analysed for total and differential leukocyte counts, markers of muscle damage (CK), lipid peroxidation (MDA), and acute phase proteins (CRP; fibrinogen; alpha-1-ACT). The total antioxidant status (TEAC) and plasma levels of the proinflammatory cytokines IL-6, IL-8, and TNF-alpha were also determined. Subjective pain reports, and plasma activities of CK, MDA, and circulatory monocytes reached peak values at 48 hrs postrace (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). TEAC and the cytokine IL-8 increased immediately after the race (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). Plasma TNF-alpha remained unchanged (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.05). Despite the reports of muscle damage and soreness, no evidence of an acute phase response was observed (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 0.05), which may be explained by the failure of the race to induce a plasma TNF-alpha response. Future studies should examine the link between muscle damage, oxidative stress, and the acute phase response following hill races of longer duration with larger eccentric components.
The aim of this study was to compare selected physiological variables and performance markers of ... more The aim of this study was to compare selected physiological variables and performance markers of soldiers from two “elite” units of the British Army. Ten soldiers from each of the two units were recruited for this study (n = 20). All participants completed three tests while carrying a 20 kg backpack load: (1) a maximal treadmill test using the Bruce protocol; (2) a 2 mile backpack run test specific to Unit A on a consistently flat tarmac road; and (3) a 29 km time-trial over hilly terrain typical of a mountainous area used by Unit B for performance assessment. Heart rate, maximal blood lactate concentration and performance (run time) were assessed during all three tests, with peak oxygen uptake also being measured during the maximal treadmill test. Measurements of anthropometry, isokinetic strength and mental toughness (MT48) were also recorded. There were no significant differences in terms of performance markers between the units (P > 0.05). Performance on the maximal treadmill test correlated with performance on the 2 mile backpack run test (r = −0.57) and 29 km time-trial (r = −0.66). Performance on the 2 mile backpack run test in turn correlated with 29 km time-trial performance (r = −0.77), accounting for 59% of the variance. In conclusion, the maximal treadmill test and the 2 mile backpack run test are useful indicators of performance on the arduous hill march and could be employed in the screening and selection of potential recruits.
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