Ingeborg C. Kowanko

Granulocyte‐macrophage colony‐stimulating factor augments neutrophil killing of Torulopsis glabrata and stimulates neutrophil respiratory burst and degranulation

The effects of granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) on the interaction between the fungus Torulopsis glabrata and human neutrophils was examined. Pre‐incubation of neutrophils with GM‐CSF increased the neutrophil fungal killing. The cytokine also increased the oxygen‐dependent respiratory burst in response to opsonized fungi, measured by the lucigenin‐dependent chemiluminescence assay and superoxide release. Under the same conditions the cytokine augmented release of constituents from both specific and azurophilic granules. Besides these priming effects, GM‐CSF was a weak stimulus of the neutrophil respiratory burst and degranulation. The priming and stimulatory effects of GM‐CSF were observed at 10–1000 U/ml with an optimal concentration of 100 U/ml.

Interleukin 2 inhibits migration and stimulates respiratory burst and degranulation of human neutrophils in vitro

Interleukin 2 (IL2) is a lymphocyte product recognised for its role as a T lymphocyte growth factor. Since some other lymphokines and monokines can modulate the function of granulocytes we examined the effects of natural and recombinant human IL2 on neutrophil locomotion, respiratory burst and degranulation. Purified T cell-derived IL2 inhibited both random and chemotactically-directed migration of neutrophils. IL2 induced a respiratory burst and release of lysosomal enzymes in neutrophils and increased these responses in classically stimulated neutrophils. Recombinant IL2 was also effective in altering neutrophil functions. We conclude that IL2 modulates neutrophil function.

Augmentation of the human monocyte/macrophage chemiluminescence response during short‐term exposure to interferon‐gamma and tumour necrosis factor‐alpha

The effects of short‐term (30 min) pre‐incubation of human monocytes and macrophages (3‐day cultured monocytes) with leucocyte‐derived human interferon‐gamma (IFN‐γ) and recombinant human tumour necrosis factor‐alpha (rTNF‐α) were examined. Pre‐incubation of either monocytes or macrophages with rTNF‐α or IFN‐γ (100 U/5 × 105 cells) augmented their respiratory burst to formyl‐L‐methionyl‐L‐leucyl‐L‐phenylalanine (fMLP), measured by the luminol‐ and lucigenin‐dependent chemiluminescence assay. In addition, both cell types showed a burst of respiratory activity in the presence of rTNF‐α or IFN‐γ only. The effects of IFN‐γ were removed by adsorption with an anti‐ IFN‐γ monoclonal antibody and those of rTNF‐α were abolished by heating at 100°C, or by the addition of anti‐TNF‐α monoclonal antibody. The results demonstrate that both IFN‐γ and rTNF‐α are stimulators of monocytes and macrophages, and rapidly alter the capacity of the cells to respond to fMLP, which binds to cell surface receptors.

Tumor necrosis factor priming of peripheral blood neutrophils from rheumatoid arthritis patients

Recently it was shown that tumor necrosis factor-α (TNF) receptors on neutrophils may be down-regulated after stimulation with proinflammatory mediators. Since in rheumatoid arthritis neutrophils are likely to encounter these mediators in the circulation, we tested the hypothesis that rheumatoid arthritis neutrophil TNF receptors are down-regulated. Peripheral blood neutrophils from patients with rheumatoid arthritis and healthy subjects were compared with respect to their TNF binding activity and ability to be primed by TNF. There were no differences between rheumatoid arthritis and control neutrophils in receptor-mediated TNF binding, superoxide release in response to agonist, and TNF priming of this respiratory burst or in the ability to degrade cartilagein vitro and TNF priming for increased cartilage damage. It is evident that rheumatoid arthritis blood neutrophils retain the ability to bind TNF and can be primed by TNF for increased oxygen radical production and augmented cartilage damage. These findings further implicate the role of neutrophils in the pathogenesis of arthritis.

Neutrophil-mediated cartilage injury in vitro is enhanced by tumour necrosis factor alpha.

SummaryNeutrophil functions relevant to tissue damage are altered by cytokines such as tumour necrosis factor alpha (cachectin, TNFα), known to be present in inflammatory foci. In this study we examined the effect of TNFα on neutrophil-mediated cartilage damage in vitro. Human neutrophils were able to injure both human and bovine articular cartilage slices by degrading proteoglycan and inhibiting its synthesis. Recombinant human TNFα enhanced neutrophil-mediated degradation of proteoglycan, even when neutrophils were preincubated with TNFα and washed before incubating with cartilage. TNFα alone degraded proteoglycan and inhibited its synthesis. Neutrophil-mediated inhibition of proteoglycan biosynthesis was increased after incubating cartilage together with neutrophils and TNFα, but was unaltered when neutrophils were preincubated with TNFα. We conclude that TNFα enhances neutrophil injury to articular cartilage.

Tumour Necrosis Factor‐β Modulates Human Neutrophil‐Mediated Cartilage Damage

Human neutrophils, when cultured with human articular cartilage coated with heal aggregated immunoglobulin G, degraded proteoglycan and inhibited its synthesis. Neutrophil‐mediated degradation of cartilage was potentiated by recombinant human tumour necrosis factor‐β (TNFβ), although TNFβ alone did not alter proteoglycan degradation. This effect was seen when TNFβ, neutrophils, and cartilage were incubated together, and also when neutrophils were preincubated with TNFβ and washed before being added to cartilage. Similar results were obtained with living and killed cartilage, in contrast, ptetreatment of neutrophils with TNFβ abrogated the neutrophil‐mediated inhibition of proteoglycan biosynthesis. There was no effect of TNFβ alone on synthesis of proteoglycan.

Effects of neutrophil migration inhibitory factors on neonatal neutrophils.

ABSTRACT: Neonatal neutrophil migration was inhibited by preincubation with a lymphokine/monokine-rich medium conditioned by phytohemagglutinin-stimulated mononuclear leucocytes. Medium conditioned by unstimulated mononuclear cells or nonconditioned medium had no effect on neonatal neutrophil migration. Similar results were obtained with adult neutrophils. Migration distances in the presence and absence of a chemotactic gradient were much lower for neutrophils from neonates than adults when comparing treatments with the corresponding medium, i.e. medium conditioned by phytohemmaglutinin-stimulated mononuclear leucocytes, medium conditioned by unstimulated mononuclear leucocytes, or medium unconditioned by mononuclear leucocytes (p < 0.01). Although locomotion of both neonatal and adult neutrophils was inhibited by treatment, the percent inhibition of random migration was slightly but significantly less for neonates than adults (p < 0.05). These results demonstrate that neutrophils from neonates are modulated by mononuclear leucocyte-derived mediators.

Degradation of human cartilage by monocytes

The effect of human peripheral blood monocytes on the degradation of human articular cartilage was studied in vitro using a radiometric assay to detect proteoglycan breakdown. The results showed that proteoglycan breakdown was increased by 60% after a 20 h exposure to monocytes (p less than 0.001).