Defective natural immunity: an early manifestation of human immunodeficiency virus infection

Cytotoxicity mediated by natural killer (NK) and lymphokine-activated killer (LAK) cells may be of significance in host defense against viral infections. This study included 347 patients infected with human immunodeficiency syndrome virus (HIV) type 1 and 110 controls. The NK cell activity, either unstimulated or stimulated with interferon-alpha (IFN-alpha) or interleukin-2 (IL-2), and the LAK cell activity were suppressed in patients, but the NK/LAK cell activity did not differ between patients with AIDS and patients without AIDS. However, the IFN-alpha-stimulated NK cell activity and LAK cell activity were reduced in patients with symptoms of HIV disease (CDCIV) when compared with asymptomatic patients (CDCII+III). When the data were analyzed by multiple linear regression, the percentage of CD4+ cells had a positive effect on these two parameters in patients without AIDS, whereas the percentage of CD4+ cells had no significant effect on unstimulated and IL-2-stimulated NK cell activity in these patients. In controls and AIDS patients, the percentage of CD4+ cells had no effect on NK/LAK cell activity in multiple linear models. The total number of CD16+ cells was low in patients compared to controls, whereas the percentages of CD16+, CD56+, and CD16+CD56+ were either normal or elevated. Therefore, the decrease in NK cell subpopulations did not contribute to the observed depression in NK/LAK cell activity in vitro. It is concluded that natural immunity is suppressed in HIV-seropositive patients primarily because of a qualitative defect of the NK/LAK cells. This qualitative defect includes a reduced responsiveness to IFN-alpha, which is progressive until the onset of symptoms, and possibly related to the loss of CD4+ cells.

Effects of glutamine on the immune system: influence of muscular exercise and HIV infection

Glutamine increased the proliferative response and the lymphokine-activated killer cell activity of blood mononuclear cells isolated from normal healthy subjects (n = 6) in a dose-dependent manner, with optimum at 0.3-1.0 mM. The relative fraction of CD3+, CD4+, CD8+, CD14+, CD16+, and CD19+ cells was not changed by glutamine at a concentration of 0.6 mM, except in the phytohemagglutinin-stimulated proliferation experiment where the fraction of CD4+, and therefore CD3+ cells, increased. The natural killer cell activity was not influenced by glutamine. Human immunodeficiency virus (HIV)-seropositive subjects (n = 8) who performed concentric bicycle exercise for 1 h at 75% of maximal O2 consumption had an overall lower phytohemagglutinin-stimulated proliferative response, compared with the HIV-seronegative control group (n = 7). The proliferation during exercise was lower in both the HIV-seropositive and the HIV-seronegative group. Addition of glutamine in vitro did not normalize the lower proliferation in the HIV-seropositive group or the attenuated proliferation seen during exercise in both groups.

The effect of acute exercise on lymphocyte subsets, natural killer cells, proliferative responses, and cytokines in HIV-seropositive persons

Eight healthy men infected with human immunodeficiency virus, type 1 (HIV) and eight HIV seronegative age- and sex-matched controls exercised on a bicycle ergometer (75% of VO2max, 1 h). The percentages of CD4+, CD4+45RA+, and CD4+45RO+ cells did not change, whereas the absolute number of CD4+ cells increased twofold during exercise and fell below prevalues 2 h after. The neutrophil count increase was more pronounced after exercise in the controls compared with in HIV-seropositive subjects. The percent CD16+ cells, and the natural killer (NK) and lymphokine activated killer (LAK) cell activity increased during exercise, but this increase was significantly less pronounced in the HIV-seropositive group. The results suggest that in response to physical stress, HIV-seropositive subjects have an impaired ability to mobilize neutrophils, NK and LAK cells to the blood. Furthermore, because the total number of CD4+ cells, but not the percentage of CD4+ cells, changed in response to exercise, this study further strengthens the idea that the percentage of CD4+ cells is preferable to the number of CD4+ cells in monitoring patients seropositive for HIV.

Bicycle exercise enhances plasma IL-6 but does not change IL-1 alpha, IL-1 beta, IL-6, or TNF-alpha pre-mRNA in BMNC

The present study investigated the effect of concentric exercise on cytokine plasma levels and cytokine pre-mRNA in blood mononuclear cells (BMNCs). Healthy young moderately trained men performed ergometer bicycle exercise for 1 h at 75% of maximal oxygen uptake. The levels of plasma interleukin (IL)-6 increased significantly during exercise, but plasma levels of IL-1 alpha, IL-1 beta, and tumor necrosis factor-alpha (TNF-alpha) were below the detection limit in most subjects. Pre-mRNA for IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha could be detected in BMNCs, but the amounts did not change in relation to exercise. These results indicate that, although the absolute number of monocytes increases during exercise and the percentage of CD14+/HLA-DR+ and CD14+/HLA-DR- monocytes increases after exercise, the increased plasma levels of IL-6 during exercise is not likely to be a result of activated monocytes in peripheral blood.

NK cell response to physical activity: possible mechanisms of action

Natural killer (NK) cells are highly influenced by physical exercise. The possible important mechanisms behind exercise-induced changes in NK cell function are cytokines, hyperthermia, and stress hormones, including catecholamines, growth hormone, cortisol, and beta-endorphins. Infusion studies mimicking stress hormone levels in blood during exercise indicate that increased plasma-adrenaline accounts for at least part of the exercise-induced modulation of NK cell function. During moderate as well as severe acute exercise, the NK cell activity is enhanced, but severe exercise is followed by immunodepression, at least in part caused by prostaglandins. Elite athletes have at rest elevated NK cell activity. However, due to frequent severe exercise the NK cell function is often temporarily severely depressed. It is suggested that during the time of immunodepression microorganisms, especially virus, invade the host, whereby infections can be established. However, in those who perform regular moderate exercise the immune system will often be temporarily enhanced and this will protect these from infections.