Glutamine is essential for the function of lymphocytes and macrophages, where it serves, among other things, as a source of energy. Little information is available concerning the fuel that polymorphonuclear cells use for their metabolic and bactericidal functions. It was the purpose of this study to determine whether glutamine would enhance the in vitro bactericidal function of normal neutrophils and whether the amino acid would restore the observed impaired function in burn patients to or above the normal level. Twelve burn patients with total body surface area burns ranging from 32% to 87% were studied. At various postburn times, neutrophils were isolated and their ability to kill Staphylococcus aureus in the presence and absence of glutamine was determined and compared with that in normal subjects. Glutamine enhanced the bactericidal function of normal neutrophils. In every patient, at all but two postburn times, glutamine caused an improvement in the observed abnormal neutrophil bactericidal function and often restored it to or slightly above the normal level. Glutamine had no effect on the expression of C3b receptors (CR1 or CD35) or on phagocytosis by the cells. This study confirms the beneficial effects of glutamine in at least one arm of the immune system and adds evidence for the possible advantage of including this amino acid in the diets of burn and other trauma patients.

Kupffer cells and alveolar, splenic, and peritoneal macrophages from normal rats were incubated for various periods of time in the presence of LPS, and the culture supernatants were analyzed for IL-6, IL-1, and TNF. There was very little difference in the amounts of the cytokines produced by the macrophages when stimulated with 0.01-10 micrograms/ml of LPS. The shapes of the time course curves for the production of the cytokines by the different types of macrophages were generally similar, although only Kupffer cells continued to produce IL-6 throughout the entire incubation period and splenic macrophages showed a lag period in the production of IL-1. Kupffer cells produced more IL-6 than that produced by the other populations of macrophages, and alveolar macrophages produced more IL-1 compared to that produced by splenic cells. Kupffer cells and peritoneal macrophages produced more IL-6 in 24 h than in 6 h of culture, and splenic macrophages produced more IL-1 in 24 compared to 6 h of culture. Alveolar macrophages produced more TNF than that produced by the other populations of cells but only when integrated over the entire incubation period. These results confirm and extend the observed functional heterogeneity of macrophages obtained from different tissues of the same animal. This study and future studies will lead to a better understanding of the role of cytokines in the inflammatory response.

The effect of thermal injury on the in vitro production of TNF, IL-6, and PGE2 by bone marrow-derived, LPS-stimulated rat macrophages was studied. Thermal injury caused a general hyperactivity in the production of the mediators by the cells. Indomethacin, a cyclooxygenase inhibitor of PGE2 synthesis, inhibited the production of IL-6 and PGE2 but had no effect on the production of TNF. These results suggest that the observed low concentration of PGE2 produced by the cells was insufficient to cause inhibition of TNF synthesis; thus, the effect of indomethacin would be undetectable. The results also suggest that indomethacin may act directly in inhibiting the production of IL-6 by the macrophages. The hyperactive effect of thermal injury on the production of inflammatory mediators by newly differentiated bone marrow derived macrophages can be important in the overall systemic response to the insult.

No abstract

Burn patients often experience a devastating inflammatory response to infection within the first two weeks after thermal injury. The inflammatory cytokines IL-6, TNF and IL-1 have been implicated in this condition but most studies have focused on the abnormal levels of cytokines in the plasma. In this study the production of cytokines was compared for Kupffer cells versus splenic macrophages; endotoxin (LPS) stimulation versus no stimulation; and burn (post burn days 1, 3 and 8) versus no burn (control). Corresponding serum levels of IL-6 were also determined. Kupffer cells from normal or burned animals were shown to produce much higher amounts of the inflammatory cytokines than that produced by splenic macrophages. An exception to this was the equal production of TNF by LPS-stimulated hepatic and splenic cells. Both LPS-stimulated Kupffer cells and splenic macrophages produced larger amounts of the cytokines than that produced by the unstimulated cells. There was a significant effect of thermal injury on cytokine production by LPS-stimulated Kupffer cells at post burn day 8 and on TNF production by stimulated splenic macrophages also at post burn day eight. Although there was a statistically significant effect of thermal injury at post burn day 8 on IL-1 production by unstimulated splenic macrophages, the absolute amount of cytokine produced was very small. The results suggest that by post burn day 8 the cells may have become primed to respond to a stimulus such as endotoxin (LPS), a condition that could arise in a burn patient from sepsis. Strangely, the large spike in serum IL-6 level occurred at post burn day one and the level of the cytokine returned nearly to the control value on post burn days 3 and 8.

As the applications of hematopoietic growth factors increase, their complex impact on host defense and immune responses continues to unfold. The effect of the administration of granulocyte colony-stimulating factor (G-CSF) on bacterial defense, proliferation of lymphocytes, and cytokine production by lymphocytes and peripheral blood mononuclear cells (PBMC) was studied. The effect of G-CSF administration on the phenotype of the cells in the major hematopoietic organs was studied as well. ACI rats were given 10 mg/kg/day G-CSF or vehicle daily for 4 days. Isolated bone marrow neutrophils and enterocytes from treated animals showed a greater bactericidal activity than controls. Proliferation of mitogen-stimulated lymphocytes and PBMC was reduced in G-CSF-treated animals. The production of proinflammatory cytokines, tumor necrosis factor (TNF), and interleukin 6 (IL-6) by lymphocytes and PBMC was reduced by G-CSF pretreatment. G-CSF administration caused an increase in IL-4 (Th2 cytokine) release and a decrease in interferon-gamma (IFNgamma, Th1 cytokine) release by mitogen-stimulated lymphocytes. Cytometric analysis of cells in the progenitor cell region indicated a large increase in immature cells in the bone marrow of G-CSF-treated animals compared with sham along with an increase in B cells and a decrease in polymorphonuclear leukocytes (PMNs). In addition, cytometric analysis showed a large increase in PMNs in blood and splenocytes of the treated animals compared with sham. This study confirms and extends previous observations that G-CSF administration has a number of effects that might simultaneously enhance host defense while reducing the risk of developing uncontrolled systemic inflammation. This may also be efficacious in prolonging graft survival and reducing graft vs. host disease.

No abstract

These observations may be important because, as gut integrity is compromised after thermal injury, enterocytes that may have previously been unexposed or less exposed to endotoxin can become a significant source of inflammatory cytokines.