Fever and acute-phase response induced in rabbits by intravenous and intracerebroventricular injection of interleukin-6

Interleukin 6: at the interface of human health and disease

Interleukin 6 (IL-6) is a pleiotropic cytokine executing a diverse number of functions, ranging from its effects on acute phase reactant pathways, B and T lymphocytes, blood brain barrier permeability, synovial inflammation, hematopoiesis, and embryonic development. This cytokine empowers the transition between innate and adaptive immune responses and helps recruit macrophages and lymphocytes to the sites of injury or infection. Given that IL-6 is involved both in the immune homeostasis and pathogenesis of several autoimmune diseases, research into therapeutic modulation of IL-6 axis resulted in the approval of a number of effective treatments for several autoimmune disorders like neuromyelitis optica spectrum disorder (NMOSD), rheumatoid arthritis, juvenile idiopathic arthritis, polyarticular juvenile idiopathic arthritis, giant cell arteritis (GCA), and cytokine release syndrome, associated with SARS-CoV2 pneumonia. This review discusses downstream inflammatory pathways of IL-6 expression and therapeutic applications of IL-6 blockade, currently investigated for the treatment of several other autoimmune conditions such as autoimmune encephalitis, autoimmune epilepsy, as well as myelin oligodendrocyte glycoprotein associated demyelination (MOGAD). This review further highlights the need for clinical trials to evaluate IL-6 blockade in disorders such neuropsychiatric lupus erythematosus (SLE), sarcoidosis and Behcet's.

Interleukin-6 producing pheochromocytoma/paraganglioma: case series from a tertiary referral centre for pheochromocytomas and paragangliomas

INTRODUCTION

In addition to catecholamines, pheochromocytomas and paragangliomas (PPGL) may secrete interleukin-6 (IL-6). IL-6 contributes to the development of unusual symptoms, which may hinder the diagnosis.

PATIENTS AND METHODS

We report the clinical course and subsequent treatment of IL-6 producing PPGL in three patients from a single tertiary referral centre for PPGL patients in the Netherlands.

CONCLUSION

PPGL combined with persistent elevated inflammatory markers, either in the presence or absence of pyrexia, raised suspicion of IL-6 overproduction in these three patients. Although surgical resection of the tumour is the only curative treatment option, our case series adds to the accumulating evidence that alpha-blockers might be effective in these patients.

Interleukin-6 primarily produced by non-hematopoietic cells mediates the lipopolysaccharide-induced febrile response

Interleukin-6 (IL-6) is critical for the lipopolysaccharide (LPS)-induced febrile response. However, the exact source(s) of IL-6 involved in regulating the LPS-elicited fever is still to be identified. One known source of IL-6 is hematopoietic cells, such as monocytes. To clarify the contribution of hematopoietically derived IL-6 to fever, we created chimeric mice expressing IL-6 selectively either in cells of hematopoietic or, conversely, in cells of non-hematopoietic origin. This was performed by extinguishing hematopoietic cells in wild-type (WT) or IL-6 knockout (IL-6 KO) mice by whole-body irradiation and transplanting them with new stem cells. Mice on a WT background but lacking IL-6 in hematopoietic cells displayed normal fever to LPS and were found to have similar levels of IL-6 protein in the cerebrospinal fluid (CSF) and in plasma and of IL-6 mRNA in the brain as WT mice. In contrast, mice on an IL-6 KO background, but with intact IL-6 production in cells of hematopoietic origin, only showed a minor elevation of the body temperature after peripheral LPS injection. While they displayed significantly elevated levels of IL-6 both in plasma and CSF compared with control mice, the increase was modest compared with that seen in LPS injected mice on a WT background, the latter being approximately 20 times larger in magnitude. These results suggest that IL-6 of non-hematopoietic origin is the main source of IL-6 in LPS-induced fever, and that IL-6 produced by hematopoietic cells only plays a minor role.

Comparison of serum zinc levels measured by inductively coupled plasma mass spectrometry in preschool children with febrile and afebrile seizures

Background

Changes in levels of trace elements have been proposed to underlie febrile seizures. Particularly, low zinc levels have been proposed as related factor of febrile seizure. In this study, we investigated whether mean serum zinc levels differed between children with febrile seizure and afebrile seizure.

Methods

Using inductively coupled plasma mass spectrometry, serum zinc levels were measured in 288 children who had been diagnosed with febrile seizures (N=248) and afebrile seizures (N=40). Mean serum zinc levels were compared between the 2 groups.

Results

Mean serum zinc level was 60.5±12.7 µg/dL in the febrile seizure group and 68.9 ±14.5 µg/dL in the afebrile seizure group. A significant difference in serum zinc levels was observed between the febrile and afebrile seizure groups (P<0.001).

Conclusions

Zinc levels in children with febrile seizure were significantly lower than those in children with afebrile seizure.

Systemic zinc redistribution and dyshomeostasis in cancer cachexia

Cachexia affects up to two thirds of all cancer patients and is a significant cause of morbidity and mortality. It is a complex metabolic syndrome associated with the underlying illness and characterized by loss of skeletal muscle tissue with or without loss of fat mass. Cachexia's other prominent clinical symptoms include anorexia, systemic inflammation, pediatric growth failure, and hypogonadism. The relationship between the symptoms of cancer cachexia and the underlying illness is unclear, and there is an urgent need for a better understanding of the pathophysiology of this syndrome. Normal Zn metabolism is often disrupted in cancer patients, but the possible effects of systemic Zn dyshomeostasis in cachexia have not been investigated. We propose that the acute phase response can mediate Zn redistribution and accumulation in skeletal muscle tissue and contribute to the activation of the ubiquitin-proteasome pathway that regulates protein catabolism. This chronic redistribution deprives Zn from other tissues and organs and compromises critical physiological functions in the body. The cardinal symptoms of Zn deficiency are anorexia, systemic inflammation, growth failure in children, and hypogonadism. These symptoms also prominently characterize cancer cachexia suggesting that the role of systemic Zn dyshomeostasis in cachexia should be investigated.

The role of interleukin-6 in lipopolysaccharide-induced fever by mechanisms independent of prostaglandin E2

Fever has been shown to be elicited by prostaglandin E(2) (PGE(2)) binding to its receptors on thermoregulatory neurons in the anterior hypothalamus. The signals that trigger PGE(2) production are thought to include proinflammatory cytokines, such as IL-6. However, although the presence of IL-6 is critical for fever, IL-6 by itself is not or only weakly pyrogenic. Here we examined the relationship between IL-6 and PGE(2) in lipopolysaccharide (LPS)-induced fever. Immune-challenged IL-6 knockout mice did not produce fever, in contrast to wild-type mice, but the expression of the inducible PGE(2)-synthesizing enzymes, cyclooxygenase-2 and microsomal prostaglandin E synthase-1, was similarly up-regulated in the hypothalamus of both genotypes, which also displayed similarly elevated PGE(2) levels in the cerebrospinal fluid. Nevertheless, both wild-type and knockout mice displayed a febrile response to graded concentrations of PGE(2) injected into the lateral ventricle. There was no major genotype difference in the expression of IL-1beta and TNFalpha or their receptors, and pretreatment of IL-6 knockout mice with soluble TNFalpha receptor ip or intracerebroventricularly or a cyclooxygenase-2 inhibitor ip did not abolish the LPS unresponsiveness. Hence, although IL-6 knockout mice have both an intact PGE(2) synthesis and an intact fever-generating pathway downstream of PGE(2), endogenously produced PGE(2) is not sufficient to produce fever in the absence of IL-6. The findings suggest that IL-6 controls some factor(s) in the inflammatory cascade, which render(s) IL-6 knockout mice refractory to the pyrogenic action of PGE(2), or that it is involved in the mechanisms that govern release of synthesized PGE(2) onto its target neurons.

Regulation of a lymphocyte-endothelial-IL-6 trans-signaling axis by fever-range thermal stress: hot spot of immune surveillance

The pleiotropic cytokine, interleukin-6 (IL-6), has emerged in recent years as a key regulator of the transition from innate to adaptive immunity through its ability to modulate leukocyte recruitment at inflammatory sites. This review highlights a newly identified role for IL-6 trans-signaling, initiated by an agonistic complex of IL-6 and a soluble form of IL-6 receptor alpha, in heightening immune surveillance of peripheral lymphoid organs during febrile inflammatory responses. Inflammatory cues provided by the thermal component of fever trigger IL-6 trans-signaling to act at discrete levels in the multistep adhesion cascade that governs the entry of blood-borne lymphocytes across 'gatekeeper' high endothelial venules (HEVs) in lymph nodes and Peyer patches. IL-6 trans-signaling-dependent mechanisms have been elucidated during thermal stimulation of primary tethering and rolling of lymphocytes along the lumenal surface of HEVs as well as during secondary firm arrest of lymphocytes in HEVs prior to their migration into the underlying parenchyma. These mechanisms profoundly increase the probability that lymphocytes that continuously patrol the body will engage in productive encounters with target antigens sequestered within lymphoid organs. Findings that the lymphocyte-HEV-IL-6 trans-signaling biological axis functions as a thermally-sensitive alert system that promotes immune surveillance provide insight into one of the unresolved mysteries in immunology regarding the benefits of mounting a febrile reaction during inflammation.

Circulating interleukin-6 induces fever through a STAT3-linked activation of COX-2 in the brain

Interleukin (IL)-6 is an important humoral mediator of fever following infection and inflammation and satisfies a number of criteria for a circulating pyrogen. However, evidence supporting such a role is diminished by the moderate or even absent ability of the recombinant protein to induce fever and activate the cyclooxygenase-2 (COX-2) pathway in the brain, a prerequisite step in the initiation and maintenance of fever. In the present study, we investigated the role of endogenous circulating IL-6 in a rodent model of localized inflammation, by neutralizing its action using a specific antiserum (IL-6AS). Rats were injected with LPS (100 microg/kg) or saline into a preformed air pouch in combination with an intraperitoneal injection of either normal sheep serum or IL-6AS (1.8 ml/rat). LPS induced a febrile response, which was accompanied by a significant rise in plasma IL-6 and nuclear STAT3 translocation in endothelial cells throughout the brain 2 h after treatment, including areas surrounding the sensory circumventricular organs and the median preoptic area (MnPO), important regions in mediating fever. These responses were abolished in the presence of the IL-6AS, which also significantly inhibited the LPS-induced upregulation of mRNA expression or immunoreactivity (IR) of the inducible form of COX, the rate-limiting enzyme for PGE2-synthesis. Interestingly, nuclear signal transducer and activator of transcription (STAT)3-positive cells colocalized with COX-2-IR, signifying that IL-6-activated cells are directly involved in PGE2 production. These observations suggest that IL-6 is an important circulating pyrogen that activates the COX-2-pathway in cerebral microvasculature, most likely through a STAT3-dependent pathway.

Asymmetrical distribution of brain interleukin-6 depends on lateralization in mice

The central nervous system can regulate the peripheral immune system. Moreover, differences between left and right hemispheres (neurochemical brain asymmetries) and behavioral lateralization (functional brain asymmetries) affect immune responses. The molecular basis of brain-immune interactions remains insufficiently understood. Cytokines regulate immune responses, possibly through activation of the hypothalamic-pituitary-adrenal (HPA) axis. HPA axis activities are related to behavioral lateralization and brain asymmetry. Given IL-6 plays a role in asymmetrical brain immunomodulation, one might expect the IL-6 distribution in brain to be asymmetrical and to depend on behavioral lateralization. In order to start to test this hypothesis, male C57BL/6J mice were selected for paw preference and assessed for IL-6 levels in right and left cortex and hippocampus by enzyme linked immunosorbent assay. The results showed asymmetrical distribution of brain IL-6 in left-pawed animals and ambidextrous animals, but not in right-pawed animals, both in cortex and hippocampus. Furthermore, we found a correlation between IL-6 hemispheric distribution and the degree of behavioral lateralization both in cortex and hippocampus. Altogether, these results suggest that brain IL-6 could be a mediator of asymmetrical immunomodulation by the central nervous system.

Intracerebroventricular interleukin-6, macrophage inflammatory protein-1 beta and IL-18: pyrogenic and PGE(2)-mediated?

This study was undertaken to determine whether cyclooxygenase (COX)-2, the critical enzyme in the production of febrigenic prostaglandin (PG) E(2), may be involved centrally in the fever induced in mice by homologous interleukin (IL)-6, macrophage inflammatory protein (MIP)-1 beta, and interleukin (IL)-18, a member of the pyrogenic IL-1 beta family. To this end, the core temperatures (Tc) of COX-1 and COX-2 gene-ablated mice and of their normal wild-type (WT) counterparts were recorded after intracerebroventricular (i.c.v.) challenge with recombinant murine (rm) IL-6 (10 ng/mouse), rmMIP-1 beta (20 pg/mouse), rmIL-18 (0.01-1 microgram/mouse), rmIL-1 beta (positive control; 0.1 microgram/mouse), or their vehicle (0.1% bovine serum albumin [BSA] in sterile phosphate-buffered saline [PBS]; 5 microl/mouse). rmIL-6 caused a approximately 1 degrees C T(c) rise in WT mice that peaked at approximately 120 min and gradually recovered over the next 3 h; COX-1(-/-) mice exhibited a relatively faster (peak at 45 min) and shorter (recovery at 150 min) febrile course, whereas COX-2(-/-) mice did not develop fever. rmMIP-1 beta induced a 1 degrees C fever (peak at 60 min) with a long time course (recovery incomplete at 300 min) in both WT and COX-2(-/-) mice; COX-1(-/-) mice displayed a quick-onset (peak at 40 min) and shorter (recovery at approximately 240 min) fever. rmIL-18 did not cause any thermal response at any dose whether administered intraperitoneally (i.p.) or i.c.v. in WT mice; COX gene-ablated mice, therefore, were not tested. These data indicate that COX-2-dependent PGE(2) is critical for the febrile response to IL-6, but not to MIP-1 beta. IL-18 i.p. or i.c.v. is not pyrogenic.

Fever induction by localized subcutaneous inflammation in guinea pigs: the role of cytokines and prostaglandins

In guinea pigs, dose-dependent febrile responses can be induced by injection of a high (100 micro g/kg) or low (10 micro g/kg) dose of bacterial lipopolysaccharide (LPS) into artificial subcutaneously implanted Teflon chambers. In this fever model, LPS does not enter the systemic circulation from the site of localized tissue inflammation in considerable amounts but causes a local induction of the proinflammatory cytokines tumor necrosis factor (TNF) and interleukin-6 (IL-6), which can be measured in lavage fluid collected from the chamber area. Only in response to the high LPS dose, small traces of TNF are measurable in blood plasma. A moderate increase of circulating IL-6 occurs in response to administration of both LPS doses. To investigate the putative roles of TNF and prostaglandins in this fever model, a neutralizing TNF binding protein (TNF-bp) or a nonselective inhibitor of cyclooxygenases (diclofenac) was injected along with the high or low dose of LPS into the subcutaneous chamber. In control groups, both doses of LPS were administered into the chamber along with the respective vehicles for the applied drugs. The fever response to the high LPS dose remained unimpaired by treatment with TNF-bp despite an effective neutralization of bioactive TNF in the inflamed tissue area. In response to the low LPS dose, there was an accelerated defervescence under the influence of TNF-bp. Blockade of prostaglandin formation with diclofenac completely abolished fever in response to both LPS doses. In conclusion, prostaglandins seem to be essential components for the manifestation of fever in this model.

The effect of interleukin-6 on L-selectin levels on polymorphonuclear leukocytes

Interleukin-6 (IL-6) shortens the transit time of polymorphonuclear leukocytes (PMN) through the marrow and accelerates their release into the circulation. In contrast to other inflammatory stimuli, this response is associated with a decrease in L-selectin levels on circulating PMN. The present study was designed to determine the effect of IL-6 on L-selectin levels of PMN in rabbits. Recombinant human IL-6 (2 microg/kg) caused a decrease in L-selectin levels on circulating PMN 3 to 12 h after treatment (P < 0.05). L-selectin levels decreased on PMN already in the circulation for up to 4 h (P < 0.05), on PMN released from the marrow posttreatment for up to 12 h (P < 0.01) and on PMN in the marrow for up to 6 h (P < 0.05) after IL-6 treatment. We conclude that IL-6 decreases L-selectin levels on circulating PMN by demarginating PMN with low levels of L-selectin and by releasing PMN from the marrow with low levels of L-selectin. We postulate that this prolonged downregulation of L-selectin on circulating PMN could influence their recruitment into inflammatory sites.

Invited review: cytokine regulation of fever: studies using gene knockout mice

Fever is defined as a regulated rise in body temperature. The regulation of this phenomenon is accomplished by the actions of two types of endogenous cytokines, some functioning as pyrogens and others as antipyretics. Previous data obtained with the use of traditional pharmacological techniques, such as the injection of neutralizing antibodies, implicate interleukin (IL)-1 and IL-6 as endogenous pyrogens or inducers of fever. In almost all instances in which the endogenous actions of IL-1 or IL-6 are antagonized, fevers are attenuated. Other cytokines, such as tumor necrosis factor-alpha (TNF-alpha) and IL-10, are thought to act as endogenous antipyretics or inhibitors of fever. In several studies, the inhibition of TNF action has enhanced fever. Recently, mice genetically engineered to lack cytokines or their receptors in all tissues of the body have been used to examine the regulation of IL-1, IL-6, TNF, and IL-10 on fever. Data obtained with these mice shed new light on our understanding of cytokine interactions in fever and, in some instances, contradict data obtained with pharmacological methods. This review summarizes the responses of cytokine and cytokine receptor knockout mice to fevers induced by lipopolysaccharide, turpentine, and sepsis.

Interleukin-6 changes deformability of neutrophils and induces their sequestration in the lung

Interleukin-6 (IL-6) is an important mediator of both the hepatic and the bone marrow components of the acute-phase response. Previous studies from our laboratory have shown that cells released into the circulation from the marrow preferentially sequester in the lung. The present study was designed to examine the mechanism of this sequestration using a single dose of recombinant human IL-6 to stimulate the marrow in rabbits. Marrow release was monitored by labeling polymorphonuclear leukocyte (PMN) precursors in the marrow with the thymidine analogue, 5'-bromo-2-deoxyuridine (BrdU), 24 h before IL-6 treatment. This treatment caused a neutrophilia that was associated with the increase of circulating BrdU- labeled PMN (PMN(BrdU)) and morphometric studies confirmed that PMN(BrdU) released from the marrow preferentially sequestered in the lung microvessels compared to unlabeled PMN. IL-6 treatment increases PMN F-actin content (p < 0.05) that was not due to cell activation by IL-6. In vitro studies show that IL-6 treatment decreased the deformability of circulating PMN (p < 0.05). These studies confirm that IL-6 treatment causes an accelerated release of PMN from the bone marrow and shows that these newly released PMN have high levels of F-actin, are less deformable, and preferentially sequester in lung microvessels.

Interleukin-6 induces demargination of intravascular neutrophils and shortens their transit in marrow

Recombinant human interleukin-6 (IL-6) causes both a thrombocytosis and leukocytosis. The thrombocytosis is caused by an accelerating thrombocytopoiesis, but the mechanism of the leukocytosis is unknown. This study was designed to determine the relative contributions of marrow stimulation and intravascular demargination to the IL-6 induced neutrophilia. IL-6 (2 microgram/kg), administered intravenously to rabbits, caused a biphasic neutrophilia with an initial peak at 3 h and a second peak at 9 h. Using the thymidine analog 5'-bromo-2'-deoxyuridine (BrdU) to label dividing polymorphonuclear leukocytes (PMNs) in the bone marrow, we showed that IL-6 treatment mobilizes PMNs from the marginated pool into the circulating pool at 2-6 h with a decrease in L-selectin expression on PMNs and also accelerates the release of PMNs from the postmitotic pool in the bone marrow at 12-24 h. We have concluded that IL-6 causes a biphasic neutrophilia wherein the first peak results from the mobilization of PMNs into the circulating pool from the marginated pool and the second peak results from an accelerated bone marrow release of PMNs.

Phagocytosis of particulate air pollutants by human alveolar macrophages stimulates the bone marrow

Epidemiologic studies have shown an association between the level of ambient particulate matter < 10 microm (PM(10)) and cardiopulmonary mortality. We have shown that exposure of rabbits to PM(10) stimulates the bone marrow. In this study, we determined whether human alveolar macrophages (AMs) that phagocytose atmospheric PM(10) produce mediators capable of stimulating the bone marrow. AMs incubated with PM(10) for 24 h produced tumor necrosis factor-alpha in a dose-dependent manner (86.8 +/- 53.29 pg/ml with medium alone; 1,087.2 +/- 257.3 pg/ml with 0.1 mg/ml of PM(10); P < 0.02). Instillation of the supernatants from AMs incubated with 0.1 mg/ml of PM(10) into the lungs of rabbits (n = 6) increased circulating polymorphonuclear leukocyte (PMN) and band cell counts as well as shortened the PMN transit time through the bone marrow (87.9 +/- 3.3 h) compared with unstimulated human AMs (104.9 +/- 2.4 h; P < 0.01; n = 5 rabbits). The supernatants from rabbit AMs incubated with 0.1 mg/ml of PM(10) (n = 4 rabbits) caused a similar shortening in the PMN transit time through the bone marrow (91.5 +/- 1.6 h) compared with human AMs. We conclude that mediators released from AMs after phagocytosis of PM(10) induce a systemic inflammatory response that includes stimulation of the bone marrow.

Are circulating cytokines interleukin-6 and tumor necrosis factor alpha involved in chlorpyrifos-induced fever?

Oral exposure to chlorpyrifos (CHP) in the rat results in an initial hypothermic response followed by a delayed fever. Fever from infection is mediated by the release of cytokines, including interleukin-6 (IL-6) and tumor necrosis factor (TNF alpha). This study determined if the CHP-induced fever involves cytokine-mediated mechanisms similar to that of infectious fevers. Long-Evans rats were gavaged with the corn oil vehicle or CHP (10-50 mg/kg). The rats were euthanized and blood collected at various times that corresponded with the hypothermic and febrile effects of CHP. Plasma IL-6, TNF alpha, cholinesterase activity (ChE), total iron, unsaturated iron binding capacity (UIBC), and zinc were measured. ChE activity was reduced by approximately 50% 4 h after CHP. There was no effect of CHP on IL-6 when measured during the period of CHP-induced hypothermia or fever. TNF alpha levels nearly doubled in female rats 48 h after 25 mg/kg CHP. The changes in plasma cytokine levels following CHP were relatively small when compared to > 1000-fold increase in IL-6 and > 10-fold rise in TNF alpha following lipopolysaccharide (E. coli; 50 microg/kg; i.p.)-induced fever. This does not preclude a role of cytokines in CHP-induced fever. Nonetheless, the data suggest that the delayed fever from CHP is unique, involving mechanisms other than TNF alpha and IL-6 release into the circulation characteristic of infectious fevers.

A gp130 Interleukin-6 Transducer-Dependent SCID Model of Human Multiple Myeloma

Agonist antihuman gp130 transducer monoclonal antibodies (MoAbs) were used in SCID mice to grow myeloma cells whose survival and proliferation is dependent on gp130 transducer activation. The agonist anti-gp130 MoAbs neither bound to murine gp130 nor activated murine cells and, as a consequence, did not induce interleukin-6 (IL-6)–related toxicities in mice. They have a 2-week half-life in vivo when injected in the peritoneum. The agonist antibodies made possible the in vivo growth of exogenous IL-6–dependent human myeloma cells as well as that of freshly explanted myeloma cells from 1 patient with secondary plasma cell leukemia. Tumors occurred 4 to 10 weeks after myeloma cell graft and weighed 3 to 5 g. They grew as solid tumors in the peritoneal cavity and metastasized to the different peritoneal organs: liver, pancreas, spleen, and intestine. Tumoral cells were detected in blood and bone marrow of mice grafted with the XG-2 myeloma cells. Tumoral cells grown in SCID mice had kept the phenotypic characteristics of the original tumoral cells and their in vitro growth required the presence of IL-6 or agonist anti-gp130 MoAbs. Myeloma cells from 4 patients with medullary involvement persisted for more than 1 year as judged by detectable circulating human Ig. However, no tumors were detected, suggesting a long-term survival of human myeloma cells without major proliferation. These observations paralleled those made in in vitro cultures as well as the tumor growth pattern in these patients. This gp130 transducer-dependent SCID model of multiple myeloma should be useful to study various therapeutical approaches in multiple myeloma in vivo.

A gp130 Interleukin-6 Transducer-Dependent SCID Model of Human Multiple Myeloma

Agonist antihuman gp130 transducer monoclonal antibodies (MoAbs) were used in SCID mice to grow myeloma cells whose survival and proliferation is dependent on gp130 transducer activation. The agonist anti-gp130 MoAbs neither bound to murine gp130 nor activated murine cells and, as a consequence, did not induce interleukin-6 (IL-6)–related toxicities in mice. They have a 2-week half-life in vivo when injected in the peritoneum. The agonist antibodies made possible the in vivo growth of exogenous IL-6–dependent human myeloma cells as well as that of freshly explanted myeloma cells from 1 patient with secondary plasma cell leukemia. Tumors occurred 4 to 10 weeks after myeloma cell graft and weighed 3 to 5 g. They grew as solid tumors in the peritoneal cavity and metastasized to the different peritoneal organs: liver, pancreas, spleen, and intestine. Tumoral cells were detected in blood and bone marrow of mice grafted with the XG-2 myeloma cells. Tumoral cells grown in SCID mice had kept the phenotypic characteristics of the original tumoral cells and their in vitro growth required the presence of IL-6 or agonist anti-gp130 MoAbs. Myeloma cells from 4 patients with medullary involvement persisted for more than 1 year as judged by detectable circulating human Ig. However, no tumors were detected, suggesting a long-term survival of human myeloma cells without major proliferation. These observations paralleled those made in in vitro cultures as well as the tumor growth pattern in these patients. This gp130 transducer-dependent SCID model of multiple myeloma should be useful to study various therapeutical approaches in multiple myeloma in vivo.

Interleukin-6 in the fever and multiorgan crisis of pheochromocytoma

A 31-y-old black man with neurofibromatosis, alcoholism and hypertension was admitted because of abdominal pain, hematemesis and cough. In the hospital he had prolonged fever and developed a multiorgan crisis. Despite thorough investigation, no infectious cause for fever was found. Urinary catecholamines and metabolites were markedly elevated. Computerized tomography revealed a mass abutting the left kidney. A diagnosis of pheochromocytoma was made, and as soon as treatment with phenoxybenzamine and propranolol was begun, the fever resolved. Serum interleukin-6 (IL-6) concentration was initially elevated, decreased after the start of adrenergic blockade, and gradually fell to an undetectable level after surgery. These observations suggest that interleukin-6 might have been causally related to the patient's fever and possibly the multiorgan crisis.

Elevation of plasma interleukin-6 level is involved in postoperative fever following major oral and maxillofacial surgery

OBJECTIVE

The purpose of this study was to evaluate whether the changes in plasma cytokine levels including interleukin-6 (IL-6) interleukin-1 beta (IL-1 beta), and tumor necrosis factor-alpha (TNF-alpha) are involved in postoperative fever following oral and maxillofacial surgery.

STUDY DESIGN

Ten patients undergoing elective oral and maxillofacial surgery were studied. We investigated the plasma cytokine levels by using an enzyme-linked immunosorbent assay and measured the core temperature and degree of postoperative shivering and peripheral vasoconstriction after surgery. The relationships between the changes in plasma cytokine levels and postoperative fever were statistically evaluated using Spearman's rank correlation coefficients.

RESULTS

The elevation of plasma IL-6 level was significantly correlated with the increase in core temperature after surgery and with the degree of postoperative shivering and vasoconstriction, whereas the changes in plasma II-1 beta or TNF-alpha levels were not.

CONCLUSIONS

Elevation of plasma IL-6 level is probably involved in postoperative fever following oral and maxillofacial surgery.

Serum and cerebrospinal fluid zinc levels in children with febrile convulsions

The mechanisms underlying febrile convulsions (FC), which have multiple etiological factors, are not yet clear. The aim of the present study was to determine whether there were any changes in serum and cerebrospinal fluid (CSF) zinc (Zn) levels in children with febrile convulsion during seizures. A total of 102 children were included in the study, with four groups formed as follows: group A, 40 children with FC (aged 9 months to 5 years); group B. 20 children having fever without convulsion (aged 6 months to 5 years); group C, 20 children with afebrile convulsion (aged 6 months to 6 years) and group D, 22 healthy children (aged 5 months to 6 years). Serum and CSF zinc levels for groups A, B and C and serum Zn levels only for group D were measured. The serum Zn levels of 17 children in group A were again measured during healthy periods. Serum Zn levels of groups A, B, C and D had a mean of 0.70 +/- 0.10 mg/dL, 1.07 +/- 0.08 mg/dL. 1.26 +/- 0.32 mg/dL and 1.17 +/- 0.21 mg/dL, respectively, and the values of group A were lower than those of the other three groups (P < 0.001). In group B, serum Zn levels were also lower than those of groups C and D (P < 0.05). The CSF Zn levels of groups A, B and C were found to have a mean of 0.07 +/- 0.02 mg/L, 0.12 +/- 0.02 mg/L and 0.14 +/- 0.04 mg/L, respectively. In group A, the CSF Zn levels were lower than those of groups B and C (P < 0.001), and in group B they were lower than those of group C (P < 0.05). For the 17 patients in group A, serum Zn levels during healthy periods (0.87 +/- 0.10 mg/dL) were found to be higher than the values shortly after seizures, but lower than those of groups B, C and D (P < 0.001). We could not observe any relationship between zinc levels of the serum and CSF and the degree and duration of the fever. These findings suggest that serum and CSF Zn levels decreased during infectious diseases, and that this decrease was more significant in patients with FC.

Interleukin-1 receptor antagonist inhibits endotoxin fever and systemic interleukin-6 induction in the rat

Although a number of studies indicate that the pyrogenic activity of lipopolysaccharide (LPS) and/or interleukin (IL)-1 is mediated via induction of IL-6, this has been questioned by recent evidence demonstrating a dissociation between fever and circulating IL-6. The present study reexamines this relationship by use of human recombinant interleukin-1 receptor antagonist (IL-1ra). Injection of LPS (100 micrograms/kg ip) into rats induced fever (2.0 degrees C) that was significantly inhibited (P < 0.05) when IL-1ra (16 mg/kg ip) was given 1 and 2 h after LPS. The rise in plasma IL-6 preceded the febrile response by 1-1.5 h and, although the concentrations of bioactive IL-6 in plasma and cerebrospinal fluid (CSF) were not reduced at 4 h, at 2 h plasma and CSF IL-6 bioactivity was inhibited by 80 and 70%, respectively, after a single injection of IL-1ra (16 mg/kg ip). Intracerebroventricular injection of IL-1ra (200 micrograms/rat) inhibited LPS fever but did not affect the plasma IL-6 bioactivity measured 2 or 4 h after intraperitoneal LPS. These data show that peripheral IL-1 plays a part in the induction of both fever and the rise in plasma IL-6 that precedes it, and that IL-1 within the brain is also important in the induction of fever by LPS.

Fever and feeding in the rat: actions of intrahypothalamic interleukin-6 compared to macrophage inflammatory protein-1 beta (MIP-1 beta)

The chemokines, macrophage inflammatory protein-1 (MIP-1) and its subunit MIP-1 beta, induce an intense fever in the rat when they are injected directly into the anterior hypothalamic, pre-optic area (AH/POA), a region containing thermosensitive neurons. The purpose of this study was to compare the central action on body temperature (Tb) of MIP-1 beta with that of interleukin-6 (IL-6), which also has been implicated in the cerebral mechanism underlying the pathogenesis of fever. Following the stereotaxic implantation in the AH/POA of guide cannulae for repeated micro-injections, radio transmitters which monitor Tb continuously were inserted intraperitoneally in each of 15 male Sprague-Dawley rats. Each micro-injection was made in a site in the AH/POA in a volume of 1.0 microliter of pyrogen-free artificial CSF, recombinant murine MIP-1 beta, or recombinant human IL-6. MIP-1 beta in a dose of 25 pg evoked an intense fever characterized by a short latency, a mean maximum rise in Tb of 2.4 +/- 0.21 degrees C reached by 3.7 +/- 0.42 hr, and a duration exceeding 6.5 hr. Injected into homologous sites in the AH/POA, IL-6 induced a dose dependent fever of similar latency and a mean maximal increase in Tb of 1.2 +/- 0.25 degrees C, 1.8 +/- 0.15 degrees C, and 2.1 +/- 0.22 degrees C and duration of 6.2 +/- 1.28 hr, 6.7 +/- 0.49 hr, and 6.8 +/- 0.65 hr when given in doses of 25, 50, and 100 ng, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-6 enhances hepatic transferrin uptake and ferritin expression in rats

To explore a mechanism of interleukin (IL)-6-induced hypoferremia in rats, iron metabolism was investigated both in vivo and in vitro. Recombinant IL-6 was intraperitoneally administered to male Wistar rats and the serial change of parameters related to iron metabolism was examined. After administration of IL-6, plasma IL-6 concentration increased rapidly, reached its maximum in 1 hr and thereafter decreased quickly. Plasma IL-6 3 hr after IL-6 injection (50 micrograms/kg) was 3 units/ml, which is a concentration capable of inducing hepatic 125I-labeled transferrin uptake in vitro using isolated hepatocytes. Plasma iron concentration and transferrin saturation had decreased to approximately one third of the initial level within 3 hr and then recovered. Total iron binding capacity remained unchanged for 6 hr, then began to decrease. Red blood cell count and hemoglobin concentration showed no remarkable changes during this period. By ferrokinetic study with plasma that contained iron 59-labeled transferrin, the plasma iron disappearance half time, calculated from the disappearance curve, was significantly shortened from 55 min to 22 min by IL-6 treatment (p < 0.01). The ferritin concentration in the liver was increased significantly after the administration of IL-6 (p < 0.001), but transiently decreased in the spleen. The plasma ferritin showed a gradual increase during the 6-hr period after IL-6 injection. The uptake of 125I-labeled diferric transferrin by isolated hepatocytes was increased by IL-6 treatment and this increment was inhibited by addition of 100-fold excess unlabeled transferrin. On the other hand, no significant increment of 125I-labeled diferric transferrin uptake was observed in Kupffer cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of electrical stimulation or local anesthesia of the rabbit's hypothalamus on the acute phase response

The effects of electrical stimulation of the rostral hypothalamic region on the acute phase response (APR) were examined in rabbits. As indicators of APR, we measured changes in the plasma concentrations of iron, zinc, copper, and fibrinogen and changes in the red and white blood cell counts. Electrical stimulation of the rostral hypothalamic region near the preoptic and anterior hypothalamic region did not induce any aspect of the APR. However, stimulation near the anteroventral portion of the third ventricle (AV3V) induced responses that were, in part, opposite to those observed in the APR: an increase in the plasma concentration of zinc and a decrease in the circulating leukocyte count. Microinjections of procaine into the brain regions near the AV3V did not induce any changes in the plasma levels of trace metals and fibrinogen but increased the circulating leukocyte count. These results suggest that nonspecific stimulation or inhibition of the rostral hypothalamic region does not induce APR.

Early induction of IL-6 in infants undergoing major abdominal surgery

Cytokines are immunoregulatory molecules that are important mediators of the host response to stress and infection. Infants and children undergoing major surgery are particularly at risk of developing sepsis and have altered metabolic responses to surgical stress compared to adults. We have investigated the temporal sequence of cytokine responses in six infants (mean age, 11 +/- 7.5 months) undergoing pull-through operation for Hirschsprung's disease and correlated them with hemodynamic and biochemical parameters. Tumor necrosis factor (TNF-alpha), interleukin-1 beta (IL-1 beta), and interleukin-6 (IL-6) were measured by ELISA preoperatively, intraoperatively (hourly), and 24 and 48 hours postoperatively. IL-6 levels increased significantly in all cases within 2 hours of commencement of the operation (P less than .01) and were maximal 24 hours postoperatively. No significant changes in IL-1 beta levels (mean range, 70 to 110 pg/mL) were seen in these patients. TNF levels were undetectable (less than 20 pg/mL) throughout the study. Cortisol levels were increased in all patients during operation. Serum C-reactive protein levels were first detected 24 hours postoperatively and continued to increase 48 hours postoperatively. Hemodynamically, heart rate increased during the first 3 hours of operation and correlated with increase in IL-6 levels. Blood pressure and temperature changes did not correlate with cytokine levels. This study identifies IL-6 as the earliest detectable cytokine response associated with major surgery in infants. It also suggests that IL-6 can be unregulated, independently of other cytokines, in response to surgical stress.

Ki-1 positive large cell anaplastic lymphoma: multiple bone lytic lesions and interleukin-6

Ki-1-positive large cell anaplastic lymphoma (Ki-1 LCAL) is recognized as a clinicopathologic syndrome with fever, peripheral lymphadenopathy and cutaneous nodules; the neoplastic cells express Hodgkin's disease-associated antigen, Ki-1 (CD30). We review here a recent case of Ki-1 LCAL with multiple bone lesions with destruction and present additional information. Although bone absorption is reported in some cases of Ki-1 LCAL, the genesis of bone absorption is unclear. Interleukin-6 (IL-6) is an important regulator of osteoclast formation and activation and can induce bone absorption. In our case, the surgically removed tumor tissue was studied for IL-6 mRNA expression and IL-6 secretion without any stimulation. Northern blot analysis showed strong IL-6 mRNA expression in the tumor tissue and ELISA assay showed a large amount of IL-6 in culture supernatants of the tumor tissue. Based on these results, coupled with the reported evidence, we discuss the close relationship between the presence of osteolytic lesions and IL-6 production in Ki-1 LCAL.