Kinetics of splenocyte interleukin-4 production after injury and lethal endotoxin challenge

Immune dysfunction in endotoxicosis: Role of nitric oxide produced by inducible nitric oxide synthase*

OBJECTIVE

To investigate whether stimulation with lipopolysaccharide (LPS) alters cytokine production by splenocytes in mice and whether it changes the T-helper 1 (Th1)/Th2 balance. The role of nitric oxide in such immunologic changes was also explored using mice with genetic lack of inducible nitric oxide synthase (iNOS).

DESIGN

: Prospective animal study with concurrent controls.

SETTING

University research laboratory.

SUBJECTS

iNOS knockout mice and wild-type littermates.

INTERVENTIONS

iNOS knockout mice or wild-type mice were injected with LPS or saline with or without anti-interleukin (IL)-6 antibody, and survival was monitored for 7 days.

MEASUREMENTS AND MAIN RESULTS

At 24 and 48 hrs after administration, blood samples and splenocytes were obtained to examine immunologic variables. Cell surface markers and cytokine expression of splenocytes were used to characterize the Th1/Th2 balance and were measured by flow cytometry. At 48 hrs after LPS administration, the Th1/Th2 balance shifted toward Th2 predominance in wild-type mice, irrespective of the IL-6 level, whereas it showed Th1 predominance in iNOS knockout mice, and the increase of IL-6 and IL-10 in response to LPS persisted in these animals. After LPS administration, the mortality rate was significantly higher in iNOS knockout mice than in wild-type mice, irrespective of the IL-6 level.

CONCLUSIONS

These findings suggest that nitric oxide produced by iNOS during endotoxemia may be involved in down-regulation of Th1 cytokines and up-regulation of Th2 cytokines, whereas IL-6 has no such role. The increased lethality of LPS in iNOS knockout mice suggests that nitric oxide may be protective against proinflammatory cytokine-induced damage. Nitric oxide excess may increase susceptibility to nosocomial infections, so-called immunoparalysis.

The cytokine response to physical activity and training

Cytokines are soluble glycoproteins that are produced by and mediate communication between and within immune and nonimmune cells, organs and organ systems throughout the body. Pro- and anti-inflammatory mediators constitute the inflammatory cytokines, which are modulated by various stimuli, including physical activity, trauma and infection. Physical activity affects local and systemic cytokine production at different levels, often exhibiting striking similarity to the cytokine response to trauma and infection. The present review examines the cytokine response to short term exercise stress, with an emphasis on the balance between pro- and anti-inflammatory mechanisms and modulation of both innate and specific immune parameters through cytokine regulation. The effects of long term exercise on cytokine responses and the possible impact on various facets of the immune system are also discussed, with reference to both cross-sectional and longitudinal studies of exercise training. Finally, the validity of using exercise as a model for trauma and sepsis is scruti- nised in the light of physiological changes, symptomatology and outcome, and limitations of the model are addressed. Further studies, examining the effect of exercise, trauma and infection on novel cytokines and cytokine systems are needed to elucidate the significance of cytokine regulation by physical activity and, more importantly, to clarify the health implications of short and long term physical activity with respect to overall immune function and resistance to infection.

Measurement of intracellular gamma-interferon, interleukin-4, and interleukin-10 levels in patients following laparoscopic cholecystectomy

Major surgery suppresses intracellular T-cell cytokine production. Laparoscopic surgery has been reported to have no effect on in vitro lymphocyte reactivity, but its effects on intracellular cytokine production are unknown. This study measured T-cell intracellular gamma-interferon, interleukin-4 (IL-4), and interleukin-10 (IL-10), along with serum interleukin-6 (IL-6) and cortisol levels, immediately before and 1 day after laparoscopic cholecystectomy in a cohort of six Air Force and veteran patients. Stimulated intracellular levels of gamma-interferon were slightly, but not significantly, elevated during the postoperative period in all T-cell subsets. There were no postoperative changes in stimulated IL-4 or IL-10 levels. Postoperative serum IL-6 levels, but not serum cortisol levels, were significantly elevated compared to preoperative values. In conclusion, laparoscopic surgery causes slight trauma but has no effect on T-cell intracellular interferon, IL-4, and IL-10 responses.