Effects of combination of tumor necrosis factor alpha and chemotactic peptide, f-Met-Leu-Phe, on phagocytosis of opsonized microspheres by human neutrophils

Compensatory response of IL-1 gene knockout mice after pulmonary infection with Klebsiella pneumoniae

This study was designed to determine the role of interleukin (IL)-1 in the inflammatory response against experimentally induced pneumonia caused by Klebsiella pneumoniae. The host immune responses of IL-1 gene knockout (IL-1 KO) mice and immunocompetent wild-type (WT) mice were compared after pulmonary infection with K. pneumoniae. There were no significant differences between the survival rates and viable bacterial counts in lungs and blood of IL-1 KO and WT mice after pulmonary infections under different conditions. Histopathological analysis showed a similar inflammatory response in both groups of mice. However, in the early stage of infection, the level of tumour necrosis factor alpha (TNF-alpha) in homogenized lungs of IL-1 KO mice was significantly higher than in WT mice. To determine the role of endogenous TNF-alpha in the recovery of the defence mechanism in IL-1 KO mice, mice were treated with an anti-TNF-alpha mAb before infection with K. pneumoniae. The results revealed a significantly lower survival rate of anti-TNF-alpha mAb-treated IL-1 KO mice than BSA-treated IL-1 KO mice. The data suggest that compensatory production of TNF-alpha in IL-1 KO mice contributes to the host defence against K. pneumoniae infection.

Phagocytosis and chemiluminescence response of granulocytes to monodisperse latex particles of varying sizes and surface coats

The response of human granulocytes to polystyrene latex beads of diameter 0.1-7 microm was measured by luminol-dependent chemiluminescence. In all instances, the response to beads of 3-7 microm was definitely higher than with smaller beads. In protein-free medium, the chemiluminescence response was slow compared to that of opsonized zymosan, and the highest response was only 9% of the response to opsonized zymosan. Scanning electron microscopy showed that granulocytes in suspension bound the particles, occasionally by extending rope-like protrusions. When the beads were coated with albumin, the chemiluminescence diminished to about 1/3 of that seen with uncoated beads; however, preincubating the beads in serum led to a large increase with beads of 1.1 microm (to 25% of the maximal response to opsonized zymosan) and 3.19 microm (to 42%), but with the smallest beads, no increase was noted. "Priming" of the cells with tumor necrosis factor-alpha caused a further increase with serum-coated beads. When uncoated beads of 1.1 microm were tested with "primed" cells, there was an increase of 6 times in the chemiluminescence compared to un-"primed" cells.

The N-formyl methionyl peptide, formyl-methionyl-leucyl phenylalanine (fMLF) increases the lateral diffusion of complement receptor 1 (CR1/CD35) in human neutrophils; a causative role for oxidative metabolites?

The effects of the N-formyl methionyl peptide, formyl-methionyl-leucyl phenylalanine (fMLF) on the lateral mobility of the complement receptor type 1 (CR1/CD35) in glass-adherent human neutrophils were investigated, using fluorescence recovery after photobleaching (FRAP) and confocal microscopy (CSLM). It was found that addition of 0.1-1 microM fMLF increased the diffusion constant (D) of CR1/CD35 to 167-228% of controls. No effect was observed on the receptor distribution or the mobile fraction of receptors. The effect of fMLF on the lateral diffusion of CR1/CD35 could be totally inhibited by addition of pertussis toxon (PD, 250 ng/ml) or of the free radical scavenger enzymes superoxide dismutase (SOD, 2000 U/ml) and catalase (CAT, 200 U/ml), added together the results show that oxidative metabolites produced by neutrophils in response to fMLF can modulate CR1/CD35 diffusion, and indicate a regulatory role for oxygen radicals in phagocytosis.

Effects of interleukin-6 (IL-6) and transforming growth factor-beta (TGF-beta) on neutrophil elastase release

The proinflammatory cytokine interleukin-6 (IL-6) and its potential opponent, transforming growth factor-beta (TGF-beta 1), have been discussed as being involved in the regulation of inflammatory processes following trauma and infections. The aim of this study was to investigate the effect of these cytokines on the regulation of neutrophil degranulation. The posttraumatic time courses of the plasma concentrations of IL-6, and the elastase-alpha 1-proteinase-inhibitor complex as marker of degranulation in patients undergoing severe trauma were found to be highly correlated, whereas TGF-beta 1 levels were determined to be not significantly altered. The close temporal correlation of IL-6 and elastase levels could be confirmed by investigation of exudates derived from the surgical area. To prove these in vivo findings, the effect of IL-6 and TGF-beta 1 on the degranulation of isolated neutrophils of healthy donors was investigated in vitro. Pathological high IL-6 concentrations were found to be capable of inducing a significant release of lysosomal elastase in a concentration-dependent manner, whereas the degranulation was unaffected by TGF-beta 1. In conclusion, these data suggest an involvement of IL-6 in the regulation of neutrophil degranulation under pathological conditions. However, TGF-beta 1 seems to have no direct regulatory effects besides its described chemotactic function on neutrophils.

Pulmonary immunity to Pseudomonas aeruginosa in intestinally immunized rats roles of alveolar macrophages, tumor necrosis factor alpha, and interleukin-1 alpha

The aims of this study were to assess the role played by alveolar macrophages, tumor necrosis factor alpha (TNF-alpha), and interleukin-1 alpha (IL-1 alpha) in pulmonary immunity against Pseudomonas aeruginosa in animals that have been immunized via the gut-associated lymphoid tissue. Following intra-Peyer's patch immunization and subsequent intratracheal challenge with live bacteria, significantly enhanced bacterial clearance from the lungs correlated with an increase in bronchoalveolar neutrophils, increased recruitment and phagocytic activity of alveolar macrophages, and accelerated production of TNF-alpha in the bronchoalveolar space, while levels of IL-1 alpha remained low. Administration of recombinant TNF-alpha in physiological concentrations did not affect the proliferation of P. aeruginosa in vitro, but when given intratracheally to rats at the time of infection, recombinant TNF-alpha significantly increased bacterial clearance from the lungs. In these animals, phagocytic activity of bronchoalveolar neutrophils was enhanced, while the recruitment of alveolar macrophages and neutrophils remained unchanged. In acutely infected nonimmune animals, bronchoalveolar concentrations of soluble IL-1 alpha and TNF-alpha increased until the time of death. Levels of prostaglandin E2 and thromboxane B2 were similar in each experimental group. These results indicate that infection in immune animals enhanced both recruitment and phagocytic activity of alveolar macrophages as well as induced an accelerated production of TNF-alpha. In immune challenged animals, this cytokine enhanced the phagocytic activity of neutrophils and improved bacterial clearance from the lung. Levels of soluble IL-1 alpha and TNF-alpha in nonimmune rats increased consistently following infection until the time of death, thus implicating these cytokines in the pathogenesis of acute P. aeruginosa pneumonia.

Effect of glutamine on phagocytosis and bacterial killing by normal and pediatric burn patient neutrophils

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.

The effect of cytokines on bactericidal activity of murine neutrophils

A range of recombinant cytokines have now been shown to modify aspects of the phenotype and function of human and murine neutrophils. However, few reports describe modification of the bactericidal activity of neutrophils. We therefore examined the recombinant murine cytokines tumor necrosis factor-alpha (TNF-alpha, 10-1000 ng ml-1) and granulocyte macrophage-colony stimulating factor (GM-CSF, 10-1000 U ml-1) for their ability to increase the bacterial killing capacity of murine neutrophils. Neutrophils from either bone marrow (fresh or cultured), or peritoneal exudates, or abscesses, were pre-incubated with either cytokine for 30-60 min and the killing of Proteus mirabilis, Escherichia coli, or Bacteroides fragilis was examined in the presence or absence of serum over a 90 min period. Only for one combination was a small but significantly enhanced level of bacterial killing observed, the phagocytic killing of P. mirabilis by peritoneal exudate neutrophils in the presence of GM-CSF and serum. With this exception there was no enhancement of bacterial killing for the range of combinations of neutrophils and bacterial species tested. In contrast, at the concentrations tested for effect on bactericidal activity, TNF-alpha and GM-CSF were able to significantly upregulate CR3 (but not Fc gamma RII) expression on mouse neutrophils. These results indicate that upregulation of CR3 as an index of neutrophil activation does not necessarily correlate with increased bactericidal activity.

Adhesive effect of certain cytokines and other perturbants on human neutrophils

Pretreatment of normal human neutrophils with certain cytokines and other mediators caused some of the cells to become adhesive and stick to the plastic (polypropylene) incubation tubes during pretreatment and during the assay for phagocytosis of C3b.IgG-coated microspheres. Often as much as 40% of the cells were adherent to the tubes after the reaction. This sticking of the neutrophils to the plastic tubes was confirmed by increase in cytometer sipping time and by lactic dehydrogenase assay of the suspended cells and of the cells stuck on the sides of the empty incubation tubes. Only those perturbants that caused an up-regulation of C3b receptors (CR1, CD35) and in most cases caused an enhancement of phagocytosis mediated the adhesiveness of the cells. Unless these stuck cells were detached by vigorous flushing with cold buffer containing EDTA, many of the cells were not admitted into the cytometer for determination of the effect of the perturbants on binding and phagocytic capacity of the neutrophils. This observation could have implications regarding the possibility of subpopulations of neutrophils and differences in function of adherent cells versus cells in suspension. In the cases studied there was no appreciable difference between the total binding and phagocytic capacities of the adherent and suspended cells.