In vivo restoration of T cell functions by human IL-1 beta or its 163-171 nonapeptide in immunodepressed mice

The immunorestorative capacities of human (hu) IL-1 beta or its synthetic fragment 163-171 (VQGEESNDK) were assessed in vivo in mice immunodepressed by aging, sublethal irradiation, or both. Subcutaneous administration of hu rIL-1 beta into immunodepressed animals immediately after carrier (horse red blood cells, HRBC) priming could restore to normal levels Th cell activity. This was measured as the ability of spleen cells from HRBC-primed mice to induce a hapten-specific antibody response in spleen cells from nonimmune mice in vitro stimulated with the hapten-carrier conjugate TNP-HRBC. In parallel, the ability of spleen cells from hu rIL-1 beta-treated immunodepressed animals to produce T cell growth factor activity upon in vitro mitogen stimulation was also increased significantly as compared to that of untreated mice and approached that of immunocompetent controls. The immunorestorative activity of hu rIL-1 beta on Th cell activity and T cell growth factor production could be mimicked by the synthetic nonapeptide 163-171 which, at the doses used, produced in most instances even greater effects than the whole protein. Although the optimal immunorestorative doses of the 163-171 peptide were several orders of magnitude higher than those of hu rIL-1 beta, the complete lack of IL-1-like inflammatory and toxic effects suggests that the synthetic hu IL-1 beta fragment may be successfully used as immunomodulating agent in the therapy of T cell immunodeficiencies.     

Interleukin-6 is a better marker of lethality than tumor necrosis factor in endotoxin treated mice

Abstract We established a mouse model to differentiate between a lethal and non-lethal presentation of endotoxic shock. The model involved injecting different amounts of Escherichia coli LPS into C3H/HeN mice which had been 'primed' with BCG. We found that the mice receiving non-lethal and lethal doses of LPS could not be differentiated in terms of their physical symptoms for the first 8 h post-injection. Tumour necrosis factor (TNF) was detected at concentrations 2–9-fold greater in mice receiving lethal doses of LPA when compared with non-lethally injected mice. However, given that (i) the successful detection of this differential was dependent on the time of sampling and (ii) that TNF was only detected in the first 3–4 h post LPS challenge, we suggest that TNF may not be very useful as a prognostic marker in endotoxic shock. In contrast, circulating IL-6 appeared to mirror the symptoms of the endotoxic mice. The relative disappearance of IL-6 after 10 h in the non-lethally injected mice corresponded with their symptomatic recovery, while IL-6 continued to circulate up to the time of death in the lethally injected mice. Furthermore, there appeared to be a good correlation between the levels of injected LPS and the levels of IL-6 induced into the circulation. Our results suggest that IL-6, rather than TNF, may serve as a prognostic marker for endotoxic shock.     

Interleukin-1-induced neurotoxicity is mediated by glia and requires caspase activation and free radical release

Interleukin (IL)-1 expression is induced rapidly in response to diverse CNS insults and is a key mediator of experimentally induced neuronal injury. However, the mechanisms of IL-1-induced neurotoxicity are unknown. The aim of the present study was to examine the toxic effects of IL-1 on rat cortical cell cultures. Treatment with IL-1beta did not affect the viability of pure cortical neurones. However, IL-1 treatment of cocultures of neurones with glia or purified astrocytes induced caspase activation resulting in neuronal death. Neuronal cell death induced by IL-1 was prevented by pre-treatment with the IL-1 receptor antagonist, the broad spectrum caspase inhibitor Boc-Asp-(OMe)-CH(2)F or the antioxidant alpha-tocopherol. The NMDA receptor antagonist dizolcipine (MK-801) attenuated cell death induced by low doses of IL-1beta but the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX) had no effect. Inhibition of inducible nitric oxide synthase with N(omega)-nitro-l-arginine methyl ester had no effect on neuronal cell death induced by IL-1beta. Thus, IL-1 activates the IL-1 type 1 receptor in astrocytes to induce caspase-dependent neuronal death, which is dependent on the release of free radicals and may contribute to neuronal cell death in CNS diseases.     

Effect of cytokines on polymorphonuclear neutrophil infiltration in the mouse. Prostaglandin- and leukotriene-independent induction of infiltration by IL-1 and tumor necrosis factor

The i.p. injection of mice with highly purified recombinant human rIL-1 alpha or beta resulted in the rapid influx of a large number of polymorphonuclear neutrophils (PMN) into the peritoneal cavity. Significant increases in the number of PMN were induced by doses of IL-1 which ranged from 0.005 to 5 ng/injection. Interestingly the dose response for PMN influx was bell-shaped because 50 ng of IL-1 did not result in a significant increase in peritoneal PMN. IL-1 induced PMN infiltration was detectable by 1 h with peak levels of PMN obtained by about 2 h, followed by a subsequent decline by 24 h. Other cytokines, IL-2, IFN-gamma, IFN alpha beta, granulocyte-CSF, granulocyte-macrophage-CSF, IL-3, TNF-alpha, and TNF-beta were compared to IL-1 for their ability to induce a PMN influx into the peritoneum. Only TNF-alpha or TNF-beta (lymphotoxin) were able to induce a significant influx of PMN within 2 h. However, based on total protein administered, about 100 times more TNF than IL-1 was required to produce a comparable PMN infiltration. Intraperitoneal injection of inhibitors of the cyclooxygenase or lipoxygenase pathways did not inhibit the IL-1-induced influx of PMN. Also, neither IL-1 nor TNF triggered an increase in PG or leukotriene release from peritoneal cells in vitro. Furthermore, direct peritoneal injection of leukotriene B4, a potent PMN chemoattractant in vitro, did not induce any significant increase in PMN in the peritoneal cavity indicating that chemotactic activity alone is insufficient for inducing peritoneal infiltration. These results suggest that the local production of very low levels of IL-1 in vivo would be sufficient to initiate a sequence of events that results in a rapid accumulation of PMN. Because IL-1 was not chemotactic for PMN in vitro, our data suggest that IL-1 induces production of factors that are chemotactic for PMN. Alternatively, IL-1 may act on other stages of the complex sequence of events that regulates the emigration of PMN into tissue sites in vivo. The synergy apparent in PMN influx when suboptimal concentrations of IL-1 and TNF were injected suggests that the local production of very low concentrations of these cytokines in situ could play a critical role in the emigration of PMN during infection.     

Priming of macrophages with lipopolysaccharide potentiates P2X7-mediated cell death via a caspase-1-dependent mechanism, independently of cytokine production.

ATP stimulation of cell surface P2X7 receptors results in cytolysis and cell death of macrophages. Activation of this receptor in bacterial lipopolysaccharide (LPS)-activated macrophages or monocytes also stimulates processing and release of the cytokine interleukin-1beta(IL-1beta) through activation of caspase-1. The cytokine interleukin 18 (IL-18) is also cleaved by caspase-1 and shares pro-inflammatory characteristics with IL-1beta. The objective of the present study was to test the hypothesis that IL-1beta, IL-18, and/or caspase-1 activation contribute directly to macrophage cell death induced by LPS and ATP. Macrophages were cultured from normal mice or those in which genes for the P2X7 receptor, IL-1beta, IL-1alpha, IL-18, or caspase-1 had been deleted. Our data confirm the importance of the P2X7 receptor in ATP-stimulated cell death and IL-1beta release from LPS-primed macrophages. We demonstrate that prolonged stimulation with ATP leads to cell death, which is partly dependent on LPS priming and caspase-1, but independent of cytokine processing and release. We also provide evidence that LPS priming of macrophages makes them highly susceptible to the toxic effects of brief exposure to ATP, which leads to rapid cell death by a mechanism that is dependent on caspase-1 but, again, independent of cytokine processing and release.     

IL-12 receptor beta 2 (IL-12R beta 2)-deficient mice are defective in IL-12-mediated signaling despite the presence of high affinity IL-12 binding sites

Two subunits of the IL-12 receptor (IL-12R), IL-12R beta 1 and IL-12R beta 2, have been identified and cloned. Previous studies demonstrated that the IL-12R beta 1 subunit was required for mouse T and NK cells to respond to IL-12 in vivo. To investigate the role of IL-12R beta 2 in IL-12 signaling, we have generated IL-12R beta 2-deficient (IL-12R beta 2(-/-)) mice by targeted mutation in embryonic stem (ES) cells. Although Con A-activated splenocytes from IL-12R beta 2(-/-) mice still bind IL-12 with both high and low affinity, no IL-12-induced biological functions can be detected. Con A-activated splenocytes of IL-12R beta 2(-/-) mice failed to produce IFN-gamma or proliferate in response to IL-12 stimulation. NK lytic activity of IL-12R beta 2(-/-) splenocytes was not induced when incubated with IL-12. IL-12R beta 2(-/-) splenocytes were deficient in IFN-gamma secretion when stimulated with either Con A or anti-CD3 mAb in vitro. Furthermore, IL-12R beta 2(-/-) mice were deficient in vivo in their ability to produce IFN-gamma following endotoxin administration and to generate a type 1 cytokine response. IL-12-mediated signal transduction was also defective as measured by phosphorylation of STAT4. These results demonstrate that although mouse IL-12R beta 1 is the subunit primarily responsible for binding IL-12, IL-12R beta 2 plays an essential role in mediating the biological functions of IL-12 in mice.     

Purification, characterization and cytokine release function of a novel Arg-49 phospholipase A(2) from the venom of Protobothrops mucrosquamatus

Group IIA phospholipase A(2) (PLA(2)) are major components in Viperidae/Crotalidae venom. In the present study, a novel PLA(2) named promutoxin with Arg at the site 49 has been purified from the venom of Protobothrops mucrosquamatus by chromatography. It consists of 122 amino acid residues with a molecular mass of 13,656 Da assessed by MALDI-TOF. It has the structural features of snake venom group IIA PLA(2)s, but has no PLA(2) enzymatic activity. Promutoxin shows higher amino acid sequence identity to the K49 PLA(2)s (72-95%) than to D49 PLA(2)s (52-58%). Promutoxin exhibits potent myotoxicity in the animal model with as little as 1 microg of promutoxin causing myonecrosis and myoedema in the gastrocnemius muscle of mice. Promutoxin is also able to stimulate the release of IL-12, TNFalpha, IL-6 and IL-1beta from human monocytes, and induce IL-2, TNFalpha and IL-6 release from T cells, indicating that this snake venom group IIA PLA(2) is actively involved in the inflammatory process in man caused by snake venom poisoning.     

Lymphokine-activated tumor inhibition in mice. Ability of a nonapeptide of the human IL-1 beta to recruit anti-tumor reactivity in recipient mice

The ability of the VQGEESNDK synthetic peptide corresponding to fragment 163-171 of human IL-1 beta to trigger lymphokine-activated tumor inhibition (LATI) of a poorly immunogenic fibrosarcoma (CE-2) of BALB/c mice was compared to that of the whole IL-1 beta. Neither molecule inhibits in vitro proliferation of CE-2 cells. Administration at the tumor challenge site for 10 days of daily injections of 50 micrograms of peptide 163-171 induce a consistent, although limited, inhibition of tumor growth, whereas similar injections of 1 pg of IL-1 beta induced a more marked LATI. However, strong LATI was elicited when these injections were performed in mice challenged with tumor cells admixed at 1/10 cell ratio with nonreactive lymphocytes from CE-2-bearing mice. The L3T4+ lymphocyte subset is mainly responsible for this enhancement. This reaction is abolished when recipient mice are sub-lethally irradiated, treated with cyclosporin A, or when the reactivity of L3T4+ and asialo GM1+ cells is suppressed. A similarly efficient LATI is found on combining the daily peptide injections with that of 10 U of IL-2. LATI stemming from this association, too, is abolished when mice are irradiated or treated with anti-L3T4 antibody, whereas it is not affected by cyclosporin A or anti-asialo GM1 antibody. Finally, a tumor-specific immune memory is acquired by about 50% of mice after LATI induced by IL-1 beta or 163-171 peptide alone and by about 80% of mice after LATI induced by peptide and lymphocytes from tumor-bearing mice or peptide and IL-2. These findings could lead to the building of a molecularly defined system to induce efficient immune recognition of tumor cells by using a peptide that does not cause any of the several inflammation-associated changes induced by the whole IL-1 beta.     

Interleukin-1 and interleukin-1 fragments as vaccine adjuvants.

The human interleukin-1beta (IL-1beta) domain in position 163-171, comprising the amino acids VQGEESNDK, has been synthesized as a nine-amino-acid-long peptide and used in vivo as a nontoxic HCl salt. The IL-1beta nonapeptide reproduces the immunostimulatory and adjuvant effects of the whole mature IL-1beta, but does not possess any of the IL-1beta inflammatory, vasoactive, tumor-promoting, and systemically toxic effects, nor it can synergize with tumor necrosis factor alpha or other molecules in inducing toxicity and shock. The IL-1beta fragment is active as adjuvant either when administered together with the antigen or if inoculated separately; it can be physically linked to the antigen or used as a discrete peptide. Moreover, the DNA sequence encoding the IL-1beta domain has been included in an experimental DNA vaccine with positive results. Thus, immunostimulatory sequences can be identified within a pleiotropic cytokine like IL-1 and used in the rational design of novel vaccination strategies.     

Alterations in megakaryocyte and platelet compartments following in vivo IL-1 beta administration to normal mice

IL-1 has been shown to stimulate the release of granulocyte-macrophage CSF, granulocyte-CSF, and macrophage-CSF from "accessory cell populations" in vitro, and it stimulates the appearance of colony-stimulating activity in the sera of mice in vivo. This cytokine has also been proposed to act on primitive hematopoietic progenitor cells to stimulate expression of receptors for the CSF. We sought to determine whether IL-1 beta could influence platelet and/or megakaryocytes and their progenitor cells following in vivo administration to normal mice. Our results demonstrated that, although administration of IL-1 beta clearly expands the pool of megakaryocyte-CFU and acetylcholinesterase-positive megakaryocytic cells (primarily in the spleen), it causes a transient and dose-dependent reduction of circulating platelets. The associated thrombocytopenia can be abolished by splenectomy before IL-1 beta administration, and is not temporally associated with the development of splenomegaly.     

The contribution of the vagus nerve in interleukin-1beta-induced fever is dependent on dose

It has been suggested that proinflammatory cytokines communicate to the brain via a neural pathway involving activation of vagal afferents by interleukin-1beta (IL-1beta), in addition to blood-borne routes. In support, subdiaphragmatic vagotomy blocks IL-1beta-induced, brain-mediated responses such as fever. However, vagotomy has also been reported to be ineffective. Neural signaling would be expected to be especially important at low doses of cytokine, when local actions could occur, but only very small quantities of cytokine would become systemic. Here, we examined core body temperature after intraperitoneal injections of three doses of recombinat human IL-1beta (rh-IL-1beta). Subdiaphragmatic vagotomy completely blocked the fever produced by 0.1 microg/kg, only partially blocked the fever produced by 0.5 microg/kg, and had no effect at all on the fever that followed 1.0 microg/kg rh-IL-1beta. Blood levels of rh-IL-1beta did not become greater than normal basal levels of endogenous rat IL-beta until the 0.5-microg/kg dose nor was IL-1beta induced in the pituitary until this dose. These results suggest that low doses of intraperitoneal IL-1beta induce fever via a vagal route and that dose may account for some of the discrepancies in the literature.     

In vivo immunostimulating activity of the 163-171 peptide of human IL-1 beta

The stimulating effect of a synthetic nonapeptide (fragment 163-171) of human interleukin 1 beta (IL-1 beta) on antibody responses to both T helper-dependent and T helper-independent antigens was investigated. It was shown that the nonapeptide enhanced the antibody response, as evaluated in the hemolytic plaque assay, of spleen cells from mice immunized with sheep red blood cells (SRBC). The activity of the 163-171 peptide on the primary response to SRBC was dose-dependent, being maximal when the peptide was inoculated at 100 mg/kg together with the antigen. Moreover, the 163-171 peptide was also effective in enhancing the secondary response to SRBC. The effect of the 163-171 peptide was to augment the frequency of cells specific for the antigen, inasmuch as no increase was ever observed in spleen cell numbers after treatment. In all these studies, human recombinant IL-1 beta gave effects qualitatively comparable to those of the 163-171 peptide, with a maximal activity at 20 ng/kg. Both the 163-171 peptide and human recombinant IL-1 beta were also able to enhance the in vivo immune response to a T helper-independent antigen such as SIII, a poorly immunogenic polysaccharidic antigen from Streptococcus pneumoniae type III. It can therefore be proposed that this synthetic nonapeptide of human IL-1 beta may represent a good candidate for use as adjuvant in vaccines.     

Utilization of endoscopic inoculation in a mouse model of intrauterine infection-induced preterm birth: role of interleukin 1beta

A novel murine model of intrauterine infection/inflammation-induced preterm birth based on direct endoscopic intracervical inoculation is described. Using this model, we investigated infection-induced premature pregnancy loss in normal and interleukin (IL) 1beta-deficient mice. Seventy-four CD-1, HS, C57BL/6J wild type (IL-1beta+/+), and C57BL/6J IL-1beta-deficient (IL-1beta-/-) mice were inoculated intracervically using a micro-endoscope, at a time corresponding to 70% of average gestation. Intracervical injection of lipopolysaccharide (LPS) or Escherichia coli reliably induced premature birth: 100% of mice intracervically injected with LPS and 92% of mice with a positive endometrial E. coli culture delivered prematurely within 36 h after inoculation. No losses were observed in mice inoculated with saline. Pregnancy loss was associated with increased uterine tissue cyclooxygenase-2 gene expression and uterine content of IL-1beta, tumor necrosis factor alpha, macrophage inflammatory protein-1alpha, and IL-6, as well as elevation of nuclear factor-kappaB activity in uterine tissues. Although IL-1beta-/- mice exhibited decreased uterine cytokine production in response to bacteria and LPS, IL-1beta deficiency did not affect the rate of pregnancy loss. This model using direct intracervical bacterial or LPS inoculation is useful for studying preterm pregnancy loss in genetically altered mice in order to develop novel interventions for infection-associated preterm labor.     

Interaction of recombinant IL-1 and recombinant tumor necrosis factor in the induction of mouse acute phase proteins

Recombinant mouse and human IL-1 (alpha and beta forms), as well as rTNF-alpha when administered in vivo, induced the production of the mouse acute phase reactants: serum amyloid P-component (SAP), C3, and fibrinogen. The SAP response to all three rIL-1 proteins reached a maximum at a dose of 10(4) U/mouse, which corresponds to 1 to 10 micrograms of protein. The maximum in vivo response consisted of a 10-fold increase in SAP levels, a 2-fold increase in C3 levels, and a 3-fold increase in fibrinogen concentration. By contrast, rTNF-alpha induced a much smaller acute phase (AP) protein response (4-fold increase in SAP) when administered in vivo. Administration of a combination if rIL-1 and rTNF resulted in an AP response that was additive for SAP, synergistic for fibrinogen, but resulted in only the same amount of C3 induced by IL-1 alone. Both recombinant monokines induced new SAP synthesis by isolated hepatocytes in vitro with an optimal response occurring with either 1 U of rIL-1/ml per 2 x 10(5) hepatocytes or 10(-3) U/ml of rTNF. The hepatocyte response to IL-1 was of the same magnitude as the response of intact mice; however, the response to TNF was approximately 10(4) times more efficient in vitro. A mixture of the monokines induced an in vitro SAP response that was additive when suboptimal doses of rIL-1 were combined with optimal amounts of rTNF-alpha. Overall, the findings indicate that both monokines directly trigger hepatocyte synthesis of SAP and that their combined effect probably accounts for a substantial portion of the synthesis of these AP proteins in mice.     

Effect of interleukin-18 on mouse core body temperature

We have studied, using a telemetry system, the pyrogenic properties of recombinant murine interleukin-18 (rmIL-18) injected into the peritoneum of C57BL/6 mice. The effect of IL-18 was compared with the febrile response induced by human IL-1beta, lipopolysaccharide (LPS), and recombinant murine interferon-gamma (rmIFN-gamma). Both IL-1beta and LPS induced a febrile response within the first hour after the intraperitoneal injection, whereas rmIL-18 (10-200 microg/kg) and rmIFN-gamma (10-150 microg/kg) did not cause significant changes in the core body temperature of mice. Surprisingly, increasing doses of IL-18, injected intraperitoneally 30 min before IL-1beta, significantly reduced the IL-1beta-induced fever response. In contrast, the same pretreatment with IL-18 did not modify the febrile response induced by LPS. IFN-gamma does not seem to play a role in the IL-18-mediated attenuation of IL-1beta-induced fever. In fact, there was no elevation of IFN-gamma in the serum of mice treated with IL-18, and a pretreatment with IFN-gamma did not modify the fever response induced by IL-1beta. We conclude that IL-18 is not pyrogenic when injected intraperitoneally in C57BL/6 mice. Furthermore, a pretreatment with IL-18, 30 min before IL-1beta, attenuates the febrile response induced by IL-1beta.     

Distinct temporal patterns of macrophage-inflammatory protein-2 and KC chemokine gene expression in surgical injury

In the present study the regulation of CXC chemokine expression was evaluated in full-thickness abdominal wounds in mice. During the first 24 h after injury, IL-1alphabeta, KC, macrophage-inflammatory protein (MIP)-2, and monocyte chemoattractant protein-1 were the predominant cytokines and chemokines produced; TNF-alpha was not detected. Chemokine mRNA expression and protein secretion occurred in two temporal stages. The first, which reached a maximum at 6 h, was associated with high levels of IL-1alpha and KC and low levels of MIP-2. This stage could be reproduced by intradermal injection of IL-1alpha or IL-1beta and was partially blocked by injection of neutralizing Ab against IL-1alpha but not IL-1beta. In animals depleted of circulating neutrophils, chemokine expression was reduced by nearly 70% during this stage. In the second stage, which peaked at 24 h after injury, modest but significant levels of IL-1beta were detected in association with low levels of KC and high levels of MIP-2. This pattern of chemokine expression could not be mimicked by injection of IL-1alpha or IL-1beta (even with prolonged exposure), although MIP-2 expression could be partially inhibited by intradermal injection of neutralizing Ab against IL-1beta. Surprisingly, neutrophil depletion before injury resulted in sustained high levels of both KC and MIP-2 expression. These observations demonstrate that these two closely related chemokines are under distinct regulatory controls in vivo that are likely to reflect the temporally ordered participation of different cell types and/or extracellular stimuli and inhibitors.     

Transgenic expression of dominant-negative Fas-associated death domain protein in beta cells protects against Fas ligand-induced apoptosis and reduces spontaneous diabetes in nonobese diabetic mice

In type 1 diabetes, many effector mechanisms damage the beta cell, a key one being perforin/granzyme B production by CD8(+) T cells. The death receptor pathway has also been implicated in beta cell death, and we have therefore generated NOD mice that express a dominant-negative form of the Fas-associated death domain protein (FADD) adaptor to block death receptor signaling in beta cells. Islets developed normally in these animals, indicating that FADD is not necessary for beta cell development as it is for vasculogenesis. beta cells from the transgenic mice were resistant to killing via the Fas pathway in vitro. In vivo, a reduced incidence of diabetes was found in mice with higher levels of dominant-negative FADD expression. This molecule also blocked signals from the IL-1R in culture, protecting isolated islets from the toxic effects of cytokines and also marginally reducing the levels of Fas up-regulation. These data support a role for death receptors in beta cell destruction in NOD mice, but blocking the perforin/granzyme pathway would also be necessary for dominant-negative FADD to have a beneficial clinical effect.     

Differential expression of the IL-1 system components during in vitro myogenesis: implication of IL-1beta in induction of myogenic cell apoptosis

We evaluated the expression of IL-1 system by normal human myogenic cells during in vitro myogenesis and the effect of exogenous IL-1beta. Expression of IL-1alpha and beta, IL-1 receptor antagonist (IL-1Ra), IL-1RI and II, IL-1R accessory protein (IL-1RAcP) and IL-1beta converting enzyme (ICE) was studied by immunocytochemistry, immunoblotting, ELISA and RT - PCR. Cell proliferation was evaluated by [3H]thymidine incorporation, cell fusion by flow cytometry and cell death by in situ end-labelling. Human normal myogenic cells constitutively produced IL-1beta and ICE, with a maximum expression at time of cell fusion. IL-1Rs and IL-1RAcP expression reached a peak at time of commitment to fusion. Myogenic cells produced small amounts of IL-1Ra at latest stages of culture, and only the intracellular isoform. Exposure of cultures to exogenous IL-1beta (1-5 ng/ml) induced myogenic cell apoptosis, without effect on cell proliferation or fusion. IL-1beta-induced cell death was associated with morphological changes including spreading appearance of cells and alteration of cell alignment. We conclude that (1) human myogenic cells constitutively produce IL-1beta; (2) IL-1 system components are differentially expressed during in vitro myogenesis; (3) IL-1 system participates to the coordinated regulation of cell density during normal myogenesis, which could serve to control the muscle mass in vivo.     

Induction of endogenous cytokine-mRNA in circulating peripheral blood mononuclear cells by IL-2 administration to cancer patients

The lymphokine IL-2 plays a central role in immune regulation. Recent clinical trials have shown that when administered systemically either alone, or in combination with lymphokine-activated killer cells, IL-2 can cause regression of metastatic tumors in some patients with a variety of otherwise refractory cancers. To evaluate the mechanism of in vivo action of IL-2, as well as the toxicity associated with its administration, we have studied the in vivo cytokine-mRNA expression of circulating PBMC in cancer patients undergoing treatment with high dose IL-2. Before IL-2 administration, we found low level or no evidence of cytokine-mRNA expression in PBMC. After IL-2 infusion, circulating PBMC showed enhanced proliferative activity and contained significant levels of mRNA for TNF-alpha and IL-6 as well as mRNA for the p55 IL-2R, Tac, but no mRNA coding for granulocyte-monocyte-CSF and TNF-beta (lymphotoxin). IL-1 beta mRNA was expressed at very low levels in circulating PBMC after IL-2 infusion. Each of these cytokine -mRNA was, however, inducible in vitro by stimulation of PBMC with IL-2 alone. The results of these in vivo studies suggest that IL-2 may be a physiologic inducer of TNF and IL-6 which, because of their pleiotropic effects, may be important endogenous signals in the body's immune response and account for some of the physiologic changes seen in patients receiving high dose IL-2.