IL-1ra Concentrations Research Articles

Interleukin-1 receptor antagonist in newborn babies and pregnant women

We have investigated the possible role of the interleukin-1 receptor antagonist (IL-1ra) in the attenuated fever response in the newborn. Umbilical cord blood was collected from normal full-term infants (n = 12), and venous blood was obtained from afebrile, non-pregnant adults, of both genders (n = 12) and women in late pregnancy (n = 12). Plasma IL-1ra, and IL-1ra produced in vitro by peripheral blood monocytes stimulated with IL-1 alpha or LPS, were assayed by ELISA. Significantly higher concentrations of IL-1ra (P < 0.01, t test) were found in umbilical cord plasma than in plasma of non-pregnant adults. Furthermore concentrations of IL-1ra in the plasma of women in late pregnancy were significantly higher than in the plasma of neonates and non-pregnant adults (P < 0.01, Mann-Whitney rank-sum test). Neonatal monocytes failed to produce significant amounts of IL-1ra upon stimulation in vitro. The monocytes of pregnant women produced much higher concentrations of IL-1ra than the monocytes of non-pregnant adults (P < 0.01 Mann-Whitney rank-sum test). We speculate that IL-1ra may attenuate the febrile response to Gram-negative pyrogens in women in late pregnancy, and by crossing the placenta, also in the newborn.

Tumor Necrosis Factor-∝ Induces Interleukin-1∝ and Interleukin-1 Receptor Antagonist Production by Cultured Human Keratinocytes

Interleukin-1 (IL-1) may have a significant pro-inflammatory effect in the skin; an imbalance in its production has been linked to cutaneous disease processes. IL-1 receptor antagonist (IL-1ra) is a recently described competitive inhibitor of IL-1 alpha and IL-1 beta that binds to human types I and II IL-1 receptors without apparent cell activation. Human keratinocytes synthesize IL-1ra, IL-1 alpha, and IL-1 beta but fail to secrete these cytokines. This study investigated IL-1ra and IL-1 alpha accumulation by cultured keratinocytes stimulated by tumor necrosis factor-alpha (TNF-alpha), IL-3, IL-4, IL-6, IL-10, interferon-gamma, granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor, and macrophage colony-stimulating factor and by various extracellular matrix proteins, conditions that these cells may encounter in normal or inflamed skin in vivo. IL-1ra and IL-1 alpha proteins were measured by specific enzyme-linked immunosorbent assay in keratinocyte supernatants and lysates. Only TNF-alpha induced IL-1ra and IL-1 alpha production. TNF-alpha added to culture in amounts of 10 ng/ml or higher, induced a twofold increase in intracellular levels of both IL-ra and IL-1 alpha without secretion at 48 h. The IL-1ra concentration in keratinocyte lysates increased from 9.6 to 17.6 ng/ml after TNF-alpha stimulation, and the IL-1 alpha concentration increased from 1.0 to 3.3 ng/ml. Keratinocytes also exhibited comparable increases in IL-1 alpha and IL-1ra mRNA levels after 12 h in culture with TNF-alpha, as determined by in vitro hybridization to specific cDNA probes. The IL-1 alpha and IL-1ra response to TNF-alpha stimulation showed a varied pattern among different keratinocyte strains over 72 h of culture on plain plastic. In contrast, extracellular matrix proteins (laminin, fibronectin, collagen I and IV, and vitronectin) did not stimulate keratinocyte accumulation of IL-1 alpha or IL-1ra proteins after 72 h in culture. When TNF-alpha was added to cells cultured on these matrices, no change in IL-1 alpha or IL-1ra production was observed above that which could be attributed to TNF-alpha alone. In conclusion, TNF-alpha, but not the extracellular matrix proteins tested, stimulated production of intracellular IL-1 alpha and IL-1ra by keratinocytes. The ratio of IL-1ra to IL-1 alpha after TNF-alpha stimulation of keratinocytes may influence the inflammatory profile in the epidermis.

Balance of synovial fluid IL-1β and IL-1 receptor antagonist and recovery from Lyme arthritis

Borrelia burgdorferi, the causative agent of Lyme disease, is a potent inducer of interleukin-1β (IL-1β), a cytokine implicated in the pathogenesis of inflammatory arthritis. The balance between IL-1 and the IL-1 receptor antagonist (IL-1ra), a naturally occurring inhibitor of IL-1, might influence disease expression. To explore this possibility, we have done a retrospective study that compared the clinical course of Lyme arthritis in 83 patients with concentrations of IL-1β and IL-1ra in the patients' synovial fluid. Patients with high concentrations of IL-1ra and low concentrations of IL-1β had rapid resolution of attacks of arthritis, whereas patients with the reverse pattern of cytokine concentrations had long intervals to recovery. Thus, the balance between synovial fluid IL-1β and IL-1ra concentrations relates to the time to recovery from an episode of Lyme arthritis.

Effect of Interleukin-1 (IL-1) Blockade on Cytokine Synthesis: I. IL-1 Receptor Antagonist Inhibits IL-1-Induced Cytokine Synthesis and Blocks the Binding of IL-1 to Its Type II Receptor on Human Monocytes

Interleukin-1 (IL-1) induces IL-1, tumor necrosis factor alpha (TNF alpha), and IL-6 gene expression and synthesis in a variety of cells. In this study, we investigated the ability of human recombinant IL-1 receptor antagonist (IL-1ra) to inhibit IL-1-induced cytokine production in human peripheral blood mononuclear cells (PBMC) and isolated monocytes. IL-1ra alone at concentrations as high as 1 microgram/mL did not induce IL-1 alpha, IL-1 beta, TNF alpha, or IL-6 synthesis. Suppression of IL-1-induced IL-1, TNF alpha, or IL-6 synthesis was dose-dependent (P less than or equal to .0001). At a twofold molar excess, IL-1ra inhibited IL-1-induced IL-1 or TNF alpha synthesis by 50% (P less than .01); an equimolar concentration of IL-1ra inhibited synthesis of these two cytokines by over 20% (P less than .05). A 10-fold molar excess of IL-1ra over IL-1 beta reduced IL-1 beta-induced IL-1 alpha by 95% (P = .01) and IL-1 alpha-induced IL-1 beta by 73% (P less than .01). IL-1ra added to PBMC 8 hours after stimulation with IL-1 beta was still able to inhibit IL-1 alpha, TNF alpha, and IL-6 synthesis (P less than or equal to .01). A similar reduction in IL-1 beta-induced IL-1 alpha was observed when IL-1 beta was removed from the cultures after 8 hours of stimulation (P less than .05), suggesting a prolonged presence of IL-1 or restimulation of IL-1 receptors on monocytes is required for the induction of cytokines. In elutriated monocytes, a 10-fold molar excess of IL-1ra reduced IL-1 beta-induced IL-1 alpha by 82% (P less than .05), TNF alpha by 64% (P = .05), and IL-6 by 47% (P less than .05). 125I-IL-1 beta was bound to purified monocytes, cross-linked, and immunoprecipitated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a band at 85 Kd corresponding to the 68-Kd IL-1 receptor type II (IL-1RtII). Excess unlabeled IL-1 beta or IL-1ra blocked the binding of 125I-IL-1 beta to the IL-1RtII. We conclude that IL-1ra inhibits IL-1-induced cytokine synthesis and competes with IL-1 for the IL-1RtII on human monocytes.

Interleukin-1 receptor antagonist circulates in experimental inflammation and in human disease

Interleukin-1 receptor antagonist (IL-1ra) is a 22-Kd protein that shares homology with IL-1 beta, binds to the IL-1 receptor, but has no known agonist properties. This inhibitor appears to be the first cytokine whose sole function is to block the actions of another cytokine. Exogenous IL-1ra administration has been shown to reduce mortality in experimental septic shock. We now report that IL-1ra is endogenously produced and circulates in experimental inflammation and in clinical disease. After experimental endotoxemia in human volunteers, IL-1ra concentrations increase from a baseline concentration of 460 +/- 200 pg mL-1 to 14,870 +/- 290 pg mL-1 at 3 hours (P less than .05). IL-1ra is also detectable in all plasma samples from critically ill patients with a mean concentration of 8,680 +/- 2,060 pg mL-1 (range 320 to 55,370 pgs mL-1). In nonhuman primates, Escherichia coli septic shock induces elevated plasma levels of IL-4ra (P less than .05). However, in animals that eventually succumb to septic shock, Il-1ra appears in quantities presumed inadequate to block the pathologic sequelae associated with high IL-1 beta levels. The findings suggest that IL-1ra may play a role in modulating the systemic host responses to a variety of nonlethal disease states by altering the balance between cytokines and their antagonists.

Interleukin-1 Receptor Antagonist Circulates in Experimental Inflammation and in Human Disease

Abstractlnterleukin-1 receptor antagonist (IL-1ra) is a 22-Kd protein that shares homology with IL-1β, binds to the IL-1 receptor, but has no known agonist properties. This inhibitor appears to be the first cytokine whose sole function is to block the actions of another cytokine. Exogenous IL-1ra administration has been shown to reduce mortality in experimental septic shock. We now report that IL-1ra is endogenously produced and circulates in experimental inflammation and in clinical disease. After experimental endotoxemia in human volunteers, IL-1ra concentrations increase from a baseline concentration of 460 ± 200 pg mL-1 to 14,870 ± 290 pg mL-1 at 3 hours (P <. 05). IL-1ra is also detectable in all plasma samples from critically ill patients with a mean concentration of 8,680 ± 2,060 pg mL-1 (range 320 to 55,370 pgs mL-1). In nonhuman primates, Escherichia coli septic shock induces elevated plasma levels of IL-1ra (P <. 05). However, in animals that eventually succumb to septic shock, II–1ra appears in quantities presumed inadequate to block the pathologic sequelae associated with high IL-1β levels. The findings suggest that IL-1ra may play a role in modulating the systemic host responses to a variety of nonlethal disease states by altering the balance between cytokines and their antagonists.

Production of interleukin-1-receptor antagonist during experimental endotoxaemia

Interleukin-1 (IL-1) has been implicated in the pathogenesis of sepsis. IL-1-receptor antagonist (IL-1ra) is a naturally occurring inhibitor of IL-1 activity that competes with IL-1 for occupancy of cell-surface receptors but possesses no agonist activity. We induced endotoxaemia in 9 healthy human volunteers by injection of Escherichia coliendotoxin, and measured plasma concentrations of IL-1 and IL-1ra by radioimmunoassay during the next 24 h. Peak plasma concentrations of IL-1ra were about a hundred-fold greater than those of IL-1β. No IL-1 or IL-1ra were detectable in the plasma of 4 volunteers injected with saline. Our results suggest that the predominant natural response to endotoxin in man is the production of antagonist rather than agonist.

Interleukin-1 receptor antagonist competitively inhibits the binding of interleukin-1 to the type II interleukin-1 receptor

The interleukin-1 receptor antagonist (IL-1ra) inhibits the binding of interleukin-1 (IL-1) to T-cell lines possessing the type I IL-1 receptor; evidence has been published (Carter, D. B., Deibel, M. R. J., Dunn, C. J., Tomich, C. S., Laborde, A. L., Slightom, J. L., Berger, A. E., Bienkowski, M. J., Sun, F. F., McEwan, R. N., Harris, P. K. W., Yem, A. W., Waszak, G. A., Chosay, J. G., Sieu, L. C., Hardee, M. M., Zurcher-Neely, H. A., Reardon, I. M., Heinrickson, R. L., Truesdell, S. E., Shelly, J. A., Eessalu, T. E., Taylor, B. M., and Tracey, D. E. (1990) Nature 344, 633-638; Hannum, C. H., Wilcox, C. J., Arend, W. P., Joslin, F. G., Dripps, D. J., Heimdal, P. L., Armes, L. G., Sommer, A., Eisenberg, S. P., and Thompson, R. C. (1990) Nature 343, 336-340) that IL-Ira does not bind to the type II IL-1 receptor (IL-1RtII). In this study we examined the ability of human recombinant IL-1ra to block the binding of IL-1 to the IL-1RtII on human polymorphonuclear leukocytes (PMN) and Raji human B-lymphoma cells. The binding of 125I-IL-1 beta to PMN was competively inhibited by IL-1ra. IL-1 beta was more potent in inhibiting the binding of 125I-IL-1 beta than IL-1ra. Incubating PMN with 125I-IL-1ra in the presence of increasing concentrations of IL-1 beta or IL-1ra showed that IL-1 beta was an approximately 40-fold more potent inhibitor of binding of 125I-IL-1ra than unlabeled IL-1ra. The IL-1ra was approximately 500-fold less potent in inhibiting the binding of 125I-IL-1 alpha than IL-1 alpha. IL-1ra was also able to competitively inhibit binding of 125I-IL-1 beta to Raji cells. PMN or Raji cells were also incubated with 125I-IL-1 in the absence or presence of IL-1 or IL-1ra. After cross-linking of IL-1 to cells followed by specific immunoprecipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a band at 85 kDa corresponding to the 68-kDa IL-1RtII. However, in the presence of an excess of either unlabeled IL-1 or IL-1ra, the 85-kDa IL-1.IL-1RtII complex was not present. These findings demonstrate that the IL-1ra recognizes and blocks IL-1 binding to the IL-1RtII.