Binding and internalization of interleukin 1 by T cells. Direct evidence for high- and low-affinity classes of interleukin 1 receptor

Peripheral-to-central immune communication at the area postrema glial-barrier following bleomycin-induced sterile lung injury in adult rats

The pathways for peripheral-to-central immune communication (P → C I-comm) following sterile lung injury (SLI) are unknown. SLI evokes systemic and central inflammation, which alters central respiratory control and viscerosensory transmission in the nucleus tractus solitarii (nTS). These functional changes coincide with increased interleukin-1 beta (IL-1β) in the area postrema, a sensory circumventricular organ that connects P → C I-comm to brainstem circuits that control homeostasis. We hypothesize that IL-1β and its downstream transcriptional target, cyclooxygenase-2 (COX-2), mediate P → C I-comm in the nTS. In a rodent model of SLI induced by intratracheal bleomycin (Bleo), the sigh frequency and duration of post-sigh apnea increased in Bleo- compared to saline- treated rats one week after injury. This SLI-dependent change in respiratory control occurred concurrently with augmented IL-1β and COX-2 immunoreactivity (IR) in the funiculus separans (FS), a barrier between the AP and the brainstem. At this barrier, increases in IL-1β and COX-2 IR were confined to processes that stained for glial fibrillary acidic protein (GFAP) and that projected basolaterally to the nTS. Further, FS radial-glia did not express TNF-α or IL-6 following SLI. To test our hypothesis, we blocked central COX-1/2 activity by intracerebroventricular (ICV) infusion of Indomethacin (Ind). Continuous ICV Ind treatment prevented Bleo-dependent increases in GFAP + and IL-1β + IR, and restored characteristics of sighs that reset the rhythm. These data indicate that changes in sighs following SLI depend partially on activation of a central COX-dependent P → C I-comm via radial-glia of the FS.

Endocytosis of pro-inflammatory cytokine receptors and its relevance for signal transduction

The pro-inflammatory cytokines tumor necrosis factor (TNF), interleukin-1 (IL-1) and interleukin-6 (IL-6) are key players of the innate and adaptive immunity. Their activity needs to be tightly controlled to allow the initiation of an appropriate immune response as defense mechanism against pathogens or tissue injury. Excessive or sustained signaling of either of these cytokines leads to severe diseases, including rheumatoid arthritis, inflammatory bowel diseases (Crohn's disease, ulcerative colitis), steatohepatitis, periodic fevers and even cancer. Studies carried out in the last 30 years have emphasized that an elaborate control system for each of these cytokines exists. Here, we summarize what is currently known about the involvement of receptor endocytosis in the regulation of these pro-inflammatory cytokines' signaling cascades. Particularly in the last few years it was shown that this cellular process is far more than a mere feedback mechanism to clear cytokines from the circulation and to shut off their signal transduction.

The Interleukin-1 System: Physiopathology and New Insights for its Therapeutical Potential

Interleukin-1 (IL-1) is a family of polypeptides that is thought to play an important role in the regulation of the systemic response to invasive stimuli such as infection, trauma or antigenic challenge, exerting both immunopotentiating and inflammatory actions on a wide variety of cellular targets. Binding studies with radiolabeled IL-Is showed that structurally distinct receptors are present on different cell types, suggesting that the different biological activities might be the consequence of IL-1 binding to distinct receptor subtypes.

The highly detrimental activities of IL-1 represent a major drawback for its therapeutic application. Studies with IL-1 fragments have shown that the nonapeptide corresponding to the 163–171 sequence of human IL-1β is able to mimic the immunopotentiating activities of IL-1 while being devoid of its pro-inflammatory potentials, thus it might find clinical application as an immunostimulating agent. Since IL-1 is involved in some pathological conditions, strategies for anti-IL-1 therapy should also be developed. In this regard a recently characterized naturally occurring IL-1 receptor antagonist might play an important role and its structural relationships with IL-1β are hereafter discussed.

Hematopoietic growth factor receptors

The formation of the cellular constituents of the blood is regulated by a series of endogenous polypeptides with largely paracrine function. A number of these hematopoietic growth factors (HGF's), which include colony stimulating factors, interleukins, and erythropoietin, have been purified to homogeneity and cloned, which in turn has led to extensive investigations of their biochemical properties and biological effects and functions. The HGF's act on target cells by binding to receptors. The kinetics and, to an even larger extent, dynamics of the factor/receptor associations display several intriguing characteristics, most of which are still poorly understood. Herein, the biochemical characteristics of HGF's receptors as well as the binding properties, post-receptor binding events and receptor modulation resulting from the association of HGF's and their target cells are reviewed.

Investigation of 99mTc-labelling of recombinant human interleukin-2 via hydrazinonicotinamide

INTRODUCTION

Interleukin-2 (IL-2) when radiolabelled with (99m)Tc has been proved useful in imaging the side of lymphocytic infiltration in patients with autoimmune disorders and plays a significant role as a T-cell imaging agent. However, the labelling procedures used so far appeared to be rather complex and laborious. The aim of present study was to develop an efficient procedure of (99m)Tc-labelling of recombinant human interleukin-2 (rhIL-2) via hydrazinonicotinamide (HYNIC) to develop a dry kit formulation.

METHODS

Various molar ratios of rhIL-2/HYNIC (from 1:2 to 1:12) were used at the conjugation step. The conjugates were purified on a PD-10 column to remove the excess of unbound HYNIC, as well as of any aggregates. The final peptide concentration was quantified by the BCA method, and the number of HYNIC molecules incorporated into a rhIL-2 molecule was determined based on the reaction with 2-sulfobenzaldehyde. The (99m)Tc-labelling was optimized using various amounts of HYNIC-rhIL-2, (99m)Tc, SnCl(2), tricine and nicotinic acid (NA). Quality control included GF-HPLC, ITLC, SDS-PAGE and biological assay. Biodistribution studies were performed in Swiss mice and Wistar rats.

RESULTS

Generally, the highest radiolabelling yields were achieved when the HYNIC-rhIL-2 conjugates of ca. 2-4 HYNIC molecule substitution ratios were used. The optimal pH of the reaction medium was found to be in the range of 6.5 to 7.0. GF-HPLC analysis indicated that monomer and aggregates of (99m)Tc-HYNIC-rhIL-2 are formed during radiolabelling. At optimized conditions of wet radiolabelling, the (99m)Tc-HYNIC-rhIL-2 monomer was obtained with radiochemical purity >99%, specific activity of ca. 4 GBq/mg rhIL-2 and overall yield of ca. 65%. The two-vial freeze-dried kit was prepared: the first vial contained 30 μg HYNIC-rhIL-2, co-ligands, buffer and antioxidant; the second vial contained tricine and SnCl(2). The monomer of (99m)Tc-HYNIC-rhIL-2 was obtained by gel chromatography on a PD-10 column. No differences between labelled and unlabelled IL2 in terms of biological activity were observed.

CONCLUSIONS

Our study shows that rhIL-2 can be efficiently radiolabelled with (99m)Tc via HYNIC, with tricine and NA as co-ligands using a two-vial freeze-dried kit. This enables the preparation of sterile and ready-to-use (99m)Tc-HYNIC(tricine,NA)-rhIL-2 within 1 h.

Measurement of lymphokine receptors

One of the most widely studied lymphokine systems is the T lymphocyte growth factor interleukin 2 (IL-2). This unit describes two basic methods for the quantitation and biochemical characterization of IL-2 receptors. The first method employs the radioreceptor assay. Support protocols to this technique describe quantification of data via calculations of association and dissociation rates and the Scatchard plot analysis. The second approach detects cell-surface lymphokine receptors by covalently cross-linking IL-2 to its receptor. This method employs the chemical disuccinimidyl suberate (DSS) to achieve irreversible cross-linking of IL-2 to IL-2R.

Modulatory effects of chitosan adipate on the T and B lymphocyte subsets in mice

This study examined the subsets of T lymphocytes in the thymus, spleen and mesenteric lymph nodes as well as the subsets of B lymphocytes in the spleen and mesenteric lymph nodes in mice administered chitosan adipate (20 mg/kg) intraperitoneally once or four times at 24 h intervals. The results showed that chitosan adipate decreased the percentage of immature CD4⁺CD8⁺ thymic T cells and increased the percentage of mature CD4⁺ and CD8⁺ thymocytes. The most significant stimulating effect was observed after four injections. A single exposure to chitosan adipate increased the percentage of CD4⁺ mesenteric lymph node cells, but four injections of the drug increased the percentage of CD4⁺ and CD8⁺ mesenteric lymph node cells. Chitosan adipate had no effect on the subset of splenic T cells. In contrast, chitosan adipate administered either once or four times increased the percentage of CD19⁺ splenocytes but had no effect on the percentage of CD19⁺ mesenteric lymph node cells. Overall, chitosan adipate induces the maturation and differentiation of thymocytes, and regulates the number of B splenic cells and lymph node T cells irrespective of the number of doses.

Interleukin-1 (IL-1alpha and IL-1beta) and its receptors (IL-1RI, IL-1RII, and IL-1Ra) in prostate carcinoma

BACKGROUND

The principal components of the interleukin-1 (IL-1) family are two secreted factors (IL-1alpha and IL-1beta), two transmembrane receptors (IL-1RI [biologically active] and IL-1RII [inert receptor]), and a natural antagonist receptor of IL-1 function (IL-1Ra). Changes in the expression pattern of these IL-1 members have been reported to be related to disease progression. The objective of the current study was to evaluate these changes in prostatic tissue by means of immunohistochemistry and Western blot analysis.

METHODS

Immunohistochemical and Western blot analyses were performed in 20 normal samples, 35 samples of benign prostatic hyperplasia (BPH) and 27 samples from patients with prostate carcinoma (PC).

RESULTS

In normal prostate samples, immunoreactions to IL-1beta and IL-1RI were positive, whereas there were no immunoreactions observed to IL-1alpha, IL-1RII, or IL-1Ra. In BPH, in addition to immunoreactions to IL-1beta and IL-1RI, immunoreactions to IL-1alpha, IL-1RII, and IL-1Ra were observed in many samples. In samples of PC with low Gleason grade, most tumors had positive immunoreactions to IL-1alpha and IL-1RI. In samples of PC with high Gleason grade, immunoreactions were seen only to IL-1alpha, IL-1RI, and IL-1RII.

CONCLUSIONS

The current results suggested that high expression levels of IL-1alpha and IL1-RI in epithelial cells in BPH and PC samples were involved in cell proliferation and that the loss of immunoexpression of IL-1beta and IL-1Ra was a characteristic feature of PC compared with normal prostate samples and BPH. Because this loss is progressive up to a complete absence of immunoexpression in PC of high Gleason grade, the evaluation of IL-1beta and IL-1Ra in PC may be significant in assessing for malignancy.

Interleukin-1beta, clinical parameters and matched cellular-histopathologic changes of biopsied gingival tissue from periodontitis patients

OBJECTIVE

The aim of the present study was to investigate whether interleukin (IL)-1beta in diseased tissues adjacent to periodontal pockets can reflect the degree of inflammation and destruction of these tissues pathologically.

BACKGROUND

IL-1beta-dependent mechanisms have been strongly implicated in contributing to inflammation and destruction of bone and attachment loss, which are characteristic features of periodontal disease. This biochemical mediator released during pro-inflammatory processes has not been objectively integrated with clinical and histopathologic features of periodontal disease.

METHODS

Periodontitis-affected inflamed tissue and clinically nonaffected healthy gingivae were harvested from 14 periodontal patients, respectively. The severity of tissue inflammation was illustrated by clinical parameters and cellular histologic changes and quantified by histometric assessments. IL-1beta in these extracted specimens was measured with an enzyme-linked immunosorbent assay (ELISA) technique. Pathogenic roles that IL-1beta plays in gingival inflammation and pathologic tissue changes in tissue sections were analyzed statistically.

RESULTS

The overall total tissue IL-1beta, tissue concentration of IL-1beta, and percentage of inflammatory cell infiltration (PICI) determined from diseased gingivae were obviously higher than those of controls from both healthy sites of periodontitis and non-periodontitis subjects. With increasing gingival index (GI), plaque index (PlI), and probing depth (PD), there was a marked elevation in total tissue IL-1beta. Total tissue IL-1beta was significantly correlated with GI, PlI, the PICI, and tissue alterations. Polymorphonuclear leukocytes (PMNs) and monocyte-macrophage cells seemed to predominate in heavily infiltrated areas of diseased gingiva. These cell types were confirmed by immunocytochemical localization with either monoclonal mouse antihuman neutrophil elastase antibody or monoclonal mouse antihuman macrophage (CD68) antibody, respectively. Total tissue IL-1beta and the PICI were also elevated in diseased gingivae near deeper PD, while neither total IL-1beta nor tissue concentration was statistically correlated with PD. Thus, correlation analysis indicates that IL-1beta level in inflamed periodontal tissues correlates highly with clinical parameters (GI and PlI) and PICI (the degree of inflammation).

CONCLUSIONS

These observations suggest that IL-1beta plays a significant role in the pathogenic mechanisms of periodontal tissue destruction, and that measurement of tissue IL-1beta would be a valuable aid and useful for diagnostic markers of periodontal diseases.

Biological imaging for the diagnosis of inflammatory conditions

Radiopharmaceuticals used for in vivo imaging of inflammatory conditions can be conveniently classified into six categories according to the different phases in which the inflammatory process develops. The trigger of an inflammatory process is a pathogenic insult (phase I) that causes activation of endothelial cells (phase II); there is then an increase of vascular permeability followed by tissue oedema (phase III). Phase IV is characterised by infiltration of polymorphonuclear cells, and a self-limiting regulatory process called apoptosis is observed (phase V). If the inflammatory process persists, late chronic inflammation takes place (phase VI). In some pathological conditions, such as organ-specific autoimmune diseases, chronic inflammation is present early in the disease. The aim of nuclear medicine in the field of inflammation/infection is to develop noninvasive tools for the in vivo detection of specific cells and tissues. This would allow early diagnosis of initial pathophysiological changes that are undetectable by clinical examination or by other diagnostic tools, and could also be used to evaluate the state of activity of the disease during therapy. These potential applications are of great interest in clinical practice. In this review, we describe the various approaches that have been developed in the last 25 years of experience. Recent advances in the diagnosis of inflammatory processes have led to the development of specific radiopharmaceuticals that are intended to allow specific stage-related diagnosis.

The developing role of cytokines for imaging inflammation and infection

The diagnosis of inflammatory processes is an important goal in medicine. In some cases the diagnosis is easy, based on the clinical history and the physical examination of the patient. Other cases are more difficult to diagnose because they are asymptomatic or with non-specific symptoms. Thus, several imaging techniques have been developed for the diagnosis of inflammatory processes, from the simple X-ray to the more sophisticated computerised tomography, magnetic resonance imaging and nuclear medicine scan. They provide different information and their role in different diseases will be discussed in this review with particular emphasis on the expanding field of the use of radiolabelled cytokines for imaging infection/inflammation. So far, IL-1, IL-1ra, IL-2, IL-6, IL-8, IL-10, IL-12 p40, G-CSF, IFN-gamma and EGF have been radiolabelled for in vivo targetting of different leukocyte subsets with promising results for their clinical use.

Annexin 1 binds to U937 monocytic cells and inhibits their adhesion to microvascular endothelium: involvement of the alpha 4 beta 1 integrin

Annexin 1 (ANX1), a calcium-binding protein, participates in the regulation of early inflammatory responses. Whereas some of its effects depend on intracellular interactions, a growing number of observations indicate that ANX1 may also act via autocrine/paracrine functions following externalization to the outer side of the plasma membrane. We studied the effects of ANX1 on leukocyte adhesion to endothelial cells using as a model system the monocytic cell line U937 and human bone marrow microvascular endothelial cells. Exogenous rANX1, as well as endogenous ANX1 externalized by U937 differentiated in vitro, inhibited monocyte firm adhesion to vascular endothelium. Both binding of ANX1 to U937 cells and ANX1-mediated inhibition of cell adhesion involved the short N-terminal domain of the ANX1 molecule. Under experimental conditions in which ANX1 inhibited U937 adhesion to human bone marrow microvascular endothelial cells, this protein specifically colocalized with the alpha 4 integrin, and a direct interaction between ANX1 and the alpha 4 integrin could be documented by immunoprecipitation experiments. Moreover, ANX1 competed with the endothelial integrin counterreceptor, VCAM-1, for binding to alpha 4 integrin. These results indicate that ANX1 plays an important physiological role in modulating monocyte firm adhesion to the endothelium.

Regulated interaction of protein kinase Cdelta with the heterogeneous nuclear ribonucleoprotein K protein

The heterogeneous nuclear ribonucleoprotein (hnRNP) K protein recruits a diversity of molecular partners that are involved in signal transduction, transcription, RNA processing, and translation. K protein is phosphorylated in vivo and in vitro by inducible kinase(s) and contains several potential sites for protein kinase C (PKC) phosphorylation. In this study we show that K protein is phosphorylated in vitro by PKCdelta and by other PKCs. Deletion analysis and site-directed mutagenesis revealed that Ser302 is a major K protein site phosphorylated by PKCdelta in vitro. This residue is located in the middle of a short amino acid fragment that divides the two clusters of SH3-binding domains. Mutation of Ser302 decreased the level of phosphorylation of exogenously expressed K protein in phorbol 12-myristate 13-acetate-treated COS cells, suggesting that Ser302 is also a site for PKC-mediated phosphorylation in vivo. In vitro, PKCdelta binds K protein via the highly interactive KI domain, an interaction that is blocked by poly(C) RNA. Mutation of Ser302 did not alter the K protein-PKCdelta interaction in vitro, suggesting that phosphorylation of this residue alone is not sufficient to alter this interaction. Instead, binding of PKCdelta to K protein in vitro and in vivo was greatly increased by K protein phosphorylation on tyrosine residues. The ability of PKCdelta to bind and phosphorylate K protein may serve not only to alter the activity of K protein itself, but K protein may also bridge PKCdelta to other K protein molecular partners and thus facilitate molecular cross-talk. The regulated nature of the PKCdelta-K protein interaction may serve to meet cellular needs at sites of active transcription, RNA processing and translation in response to changing extracellular environment.

Preferential localization of systemically administered radiolabeled interleukin 1alpha in experimental inflammation in mice by binding to the type II receptor

Previously, we have shown that systemically administered radiolabeled interleukin 1alpha (IL-1alpha) accumulates preferentially in inflammatory foci in mice. Since inflammation is characterized by influx of leukocytes, which represent IL-1 receptor (IL-1R) positive cells, radiolabeled IL-1 may specifically localize in inflammation by binding to its receptors on infiltrated leukocytes. This hypothesis was tested in a series of studies in mice with acute focal inflammations. Evidence for specific IL-1-IL-1R interaction in induced inflammation was found: microscopic autoradiography revealed that 125I-IL-1alpha localized at the site of inflammatory cells with time; 125I-myoglobin, a similar-sized protein with no known interactions in vivo, was not retained in the inflammation. Furthermore, the uptake 125I-IL-1alpha in inflammatory tissue was significantly lower in neutropenic mice than in immunocompetent mice (0.05+/-0.004 vs. 0.65+/-0.06% ID/g at 48 h after injection, P < 0.0007). Moreover, the uptake of 125I-IL-1alpha at the inflammatory site could be blocked with the anti-IL-1R type II antibody 4E2. At 48 h after injection, the uptake with and without blocking the type II IL-1R was 0.13+/-0.01 and 0. 65+/-0.05% ID/g, respectively (P < 0.0001). These in vivo studies provide evidence that systemically administered radiolabeled IL-1alpha localizes in inflammatory tissue by specific receptor binding, predominantly by binding to the type II IL-1R.

Interleukin 1-induced calcium signalling in chondrocytes requires focal adhesions

The cytokine interleukin 1 (IL-1) is an important mediator of connective-tissue destruction in arthritic joints but the mechanisms by which IL-1 mediates signal transduction in chondrocytes is poorly understood. Previous results have indicated that IL-1 receptors co-localize with focal adhesions [Qwarnstrom, Page, Gillis and Dower (1988) J. Biol. Chem. 263, 8261-8269], discrete adhesive domains of cells that function in cell attachment and possibly in signal transduction. We have determined whether focal adhesions restrict IL-1-induced Ca2+ signalling in primary cultures of bovine chondrocytes. In cells grown for 24 h on fibronectin, the basal intracellular Ca2+ ion concentration ([Ca2+]i) was 100+/-3 nM. Optimal increases of [Ca2+]i above baseline were induced by 10 nM IL-1 (183+/-30 nM above baseline). There was no significant difference between cells plated on fibronectin or type II collagen (P>0.2; 233+/-90 nM above baseline). Ca2+ transients were significantly decreased by the inclusion of 0.5 mM EGTA in the bathing buffer (74+/-11 nM above baseline), and 1 microM thapsigargin completely blocked Ca2+ transients. Cells plated on poly-(l-lysine) or suspended cells showed no Ca2+ increases, whereas cells grown on fibronectin exhibited IL-1-induced Ca2+ responses that corresponded temporally to the time-dependent cell spreading after plating on fibronectin. Cells plated on poly-(l-lysine) and incubated with fibronectin-coated beads exhibited vinculin staining in association with the beads. In identical cell preparations, IL-1 induced a 136+/-39 nM increase of [Ca2+]i above baseline in response to 10 nM IL-1beta. There were no IL-1-induced Ca2+ increases when cells on poly-(l-lysine) were incubated with fibronectin-coated beads for only 15 min at 37 degrees C, in cells maintained for 3 h at 4 degrees C, in cells incubated with BSA beads for 3 h at 37 degrees C, or in cells pretreated with cytochalasin D. Labelling of IL-1 receptors with 125I-IL-1beta showed 3-fold more specific labelling of focal adhesion complexes in cells incubated with fibronectin-coated beads compared with cells incubated with BSA-coated beads, indicating that IL-1 receptor binding or the number of IL-1 receptors was increased in focal adhesions. These results indicate that, in chondrocytes, IL-1-induced Ca2+ signalling is dependent on focal adhesion formation and that focal adhesions recruit IL-1 receptors by redistribution in the cell membrane.

Factors affecting IL-1-mediated collagen metabolism by fibroblasts and the pathogenesis of periodontal disease: a review of the literature

Fibroblasts have been studied extensively for their contribution to connective tissue destruction in diseases where the metabolism of extracellular matrix components plays an essential part in their pathogenesis. A considerable dissolution, especially of collagen fibrils, is a well-known characteristic of the periodontal ligament and the gingival connective tissue in microbial-induced periodontal disease. Fibroblasts, responsible for the assembly of the extracellular matrix, are capable of responding directly to oral microbial challenges or indirectly, following activation of the host immune response, and can alter the composition of connective tissue in several ways: synthesis of inflammatory mediators, their receptors and antagonists; fibroblast proliferation; collagen synthesis; phagocytosis of collagen fibrils; and synthesis of proteolytic enzymes, including matrix metalloproteinases and their corresponding inhibitors. The contributions of these cellular fibroblastic properties to the pathogenesis of periodontal disease are reviewed in the context of the cytokine, interleukin-1, as the inflammatory regulator.

Interleukin-1 alpha-mediated promotion of long-term alloengraftment and short-term neutrophil expansion does not require the presence of either donor or host T cells

In earlier studies, we showed that a 14-day continuous subcutaneous infusion of recombinant human interleukin (IL)-1 accelerated neutrophil recovery and enhanced long-term chimerism in a bone marrow (BM) transplant model in which T-cell-depleted BALB/c donor BM was given to irradiated C57BL/6 fully allogeneic recipients. We have extended these studies to a model entirely devoid of donor and host T cells. In the model, donor BALB/c congenic severe combined immunodeficient (C.B-17-scid/scid) BM cells are T cell depleted. The cells are then transplanted into adult irradiated C57BL/6 hosts that have been thymectomized and treated with anti-CD4 and CD8. When IL-1 alpha was delivered subcutaneously using a mini-osmotic pump, it enhanced short-term neutrophil recovery and longer term alloengraftment despite the absence of T cells in the donors and the hosts. Therefore, T cells were not required for the promotional effects of IL-1 alpha on neutrophil recovery and alloengraftment. Studies also showed that the potency of the IL-1 alpha effects was related to the degree of donor cell engraftment, which was related to the irradiation dose and the presence of T cells. We conclude that IL-1 alpha can augment post-BM transplantation hematopoietic recovery and alloengraftment via a T-cell-independent mechanism by favoring donor allogeneic hematopoietic progenitor cell competition over limited numbers of host progenitor cells.

Synthetic alleles at position 121 define a functional domain of human interleukin-1 beta

The non-conservative substitution of the tyrosine residue at position 121 of human interleukin-1 beta (IL-1 beta) generates protein mutants showing strong reduction of the capacity to induce (a) prostaglandin E2 (PGE2) release from fibroblasts and smooth muscle cells, (b) murine T-cells proliferation and (c) activation of interleukin-6 (IL-6) gene expression. It is generally accepted that these functions are mediated by the type-I interleukin-1 receptor (IL-1RI). However, the mutant proteins maintain the binding affinity to the types-I and II IL-1 receptors, which is the same as the control IL-1 beta, suggesting that this amino acid substitution does not alter the structure of the molecule, except locally. Thus we have identified a new functional site of IL-1 beta different from the known receptor binding region, responsible for fundamental IL-1 beta functions. Moreover, we show that the same mutants maintain at least two hypothalamic functions, that is, the in vitro short-term PGE2 release from rat hypothalamus and the induction of fever in rabbits. This result suggests that there is yet another site of the molecule responsible for the hypothalamic functions, implying that multiple active sites on the IL-1 beta molecule, possibly binding to more than one receptor chain, trigger different signals.

Generation and characterization of a human monoclonal autoantibody that acts as a high affinity interleukin-1 alpha specific inhibitor

Interleukin-1 (IL-1) defines two polypeptides, IL-1 alpha and IL-1 beta, that possess a wide spectrum of biological effects. Two natural antagonists of IL-1 action have been characterized: the IL-1 receptor antagonist (IL-1Ra) and a soluble form of the type II IL-1 receptor. Neutralizing autoantibodies to IL-1 alpha have also been detected in sera of healthy individuals and patients with autoimmune or inflammatory diseases. To characterize such antibodies molecularly, we attempted to generate B cell clones producing anti-IL-1 alpha human monoclonal antibody (HuMAb) by combining Epstein-Barr virus-immortalization and CD40-activation of B lymphocytes from individuals with circulating anti-IL-1 alpha. We describe herein the generation and properties of a natural IgG4/kappa anti-IL-1 alpha monoclonal autoantibody, HuMAb X3, that bound specifically to human IL-1 alpha, but not to IL-1 beta and IL-1Ra, with a high affinity (Kd = 1.2 x 10(-10)M). HuMAb X3 inhibited IL-1 alpha binding to IL-1 receptors and neutralized biological activities of both recombinant and natural forms of IL-1 alpha. A recombinant form of HuMAb X3 was found to display identical specific IL-1 alpha antagonism. The presence of somatic mutations within X3 variable regions suggests an antigen-driven affinity maturation. This study extends the demonstration of the presence of high affinity neutralizing anti-IL-1 alpha autoantibodies that can function as a third type of IL-1 antagonist.

Interleukin-1 beta suppresses apoptosis in CD34 positive bone marrow cells through activation of the type I IL-1 receptor

Interleukin-1 is a pleiotropic cytokine that has been shown previously to suppress active cell death in T cells. Two cell surface receptors for interleukin-1 have been identified and their genes cloned, type I (IL-RI) and type II (IL-RII) receptors. In the present study, we provide evidence for a role of interleukin-1 beta in the short-term suppression of cell death both in purified CD34+/Lin- bone marrow precursors and in the GM-CSF dependent cell line TF-1. Several lines of evidence suggest that the biologic effects of IL-1 beta are mediated by activation of type I IL-1 receptors (IL-1RI) and induction of GM-CSF production. First, neutralizing antibodies to IL-1RI but not IL-1RII drastically abrogated cell survival induced by IL-1 beta in CD34+/Lin- cells and TF-1 cells. Second, neutralizing antibodies against GM-CSF abrogate cell survival supported by IL-1 both in CD34+/Lin- bone marrow cells and in the cell line TF-1. Furthermore, exposure of TF-1 cells to IL-1 beta results in a transient accumulation of GM-CSF mRNA, with a peak at 3 h, which was dramatically decreased by neutralizing anti-IL-1R1 antibodies. In contrast, neutralizing anti-IL-1RII did not change the IL-1 induced cell survival of bone marrow cells and was followed by a paradoxical increase in viable cell numbers, in c-myc and c-myb mRNA accumulation in IL-1 treated TF-1 cells. Together our results indicate that the increase in cell survival induced IL-1 beta occurs through binding to IL-1RI and the subsequent production of endogenous GM-CSF. IL-1RII does not appear to be involved in signal transduction in primary CD34+/Lin- cells but could negatively regulate the response to IL-1 beta in TF-1 cells.

The type I interleukin-1 receptor mediates fever in the rat as shown by interleukin-1 receptor subtype selective ligands

The interleukin-1 (IL-1) system possesses two distinct receptors (type I and type II) which, together with the accessory protein, mediate a multitude of responses to IL-1 alpha and IL-1 beta, including fever. So far, no receptor subtype-specific ligands have been described. Since both types of IL-1 receptors occur in the thermoregulatory areas it was unclear which IL-1 receptor type mediates fever. We report here that for a series of deletion mutants of human recombinant IL-1 beta (hrIL-1 beta), the affinity of these ligands for the type I IL-1 receptor correlates with their efficacy to evoke the fever response (hrIL-1 beta > des-SND52-54 > des-QGE48-50 > des-I56). Thus, the results suggest that agonist occupancy of the type I IL-1 receptor is essential for IL-1 beta-mediated fever.

The K protein domain that recruits the interleukin 1-responsive K protein kinase lies adjacent to a cluster of c-Src and Vav SH3-binding sites. Implications that K protein acts as a docking platform

The heterogeneous ribonucleoprotein particle (hnRNP) K protein interacts with multiple molecular partners including DNA, RNA, serine/threonine, and tyrosine kinases and the product of the proto-oncogene, Vav. The K protein is phosphorylated in vivo and in vitro on serine/threonine residues by an interleukin 1 (IL-1)-responsive kinase with which it forms a complex. In this study we set out to map the K protein domains that bind kinases. We demonstrate that the K protein contains a cluster of at least three SH3-binding sites (P1, PPGRGGRPMPPSRR, amino acids 265-278; P2, PRRGPPPPPPGRG, 285-297; and P3, RARNLPLPPPPPPRGG, 303-318) and that each one of these sites is capable of selectively engaging c-Src and Vav SH3 domains but not SH3 domains of Abl, p85 phosphatidylinositol 3-kinase, Grb-2, and Csk. We demonstrate that the K protein domain that recruits and is phosphorylated in an RNA-dependent manner by the IL-1-responsive kinase, designated KPK for K protein kinase, is contained within the 338-425-amino acid stretch and thus is contiguous but does not include the cluster of the SH3-binding sites. K protein and KPK co-immunoprecipitate from cell extracts with either c-Src or Vav, suggesting that K protein-KPK-c-Src and K protein-KPK-Vav complexes exist in vivo. Furthermore, in the context of K protein, c-Src can reactivate KPK in vitro. The succession of kinase-binding sites contained within the K protein that allow it to form multienzyme complexes and facilitate kinase cross-talk suggest that K protein may serve as a docking platform that promotes molecular interactions occurring during signal transduction.

Specific targeting of infectious foci with radioiodinated human recombinant interleukin-1 in an experimental model

In the present study, radioiodinated human recombinant interleukin-1 (IL-1) was investigated for its potential to image infectious foci in vivo in an animal model of infection. Twenty-four hours after induction of a Staphylococcus aureus abscess in the left calf muscle, mice were i.v. injected with both iodine-125 labelled IL-1 and iodine-131 labelled myoglobin, a size-matched control agent. The animals were killed for tissue biodistribution studies at 2, 6, 12, 24 and 48 h p.i. Gamma camera images were obtained at 6, 24 and 48 h after injecting mice with 123I-IL-1. Radioiodinated IL-1 rapidly cleared from the body; after 12 h the abscess was the organ with the highest activity. The absolute abscess uptake of 125I-IL-1 remained high compared to 131I-myoglobin, resulting in significantly higher abscess-to-muscle ratios of 125I-IL-1 compared to 131I-myoglobin. The ratios of 125I-IL-1 reached the ultimate value of 44.4+/-10.8 at 48 h p.i., whereas the ratios of 131I-myoglobin did not exceed 5.9+/-0.7. Gamma camera imaging revealed clearly visible abscesses. In conclusion, our results demonstrate specific retention of radioiodinated IL-1 in the abscess, presumably by interaction of IL-1 with its receptor on the inflammatory cells. The high target-to-background ratios that were obtained over the course of time indicate that the IL-1 receptor may be a valuable target for the imaging of infectious foci.

Corticotropin-releasing factor treatment upregulates interleukin-1 receptors in the mouse pituitary: reversal by dexamethasone

Intraperitoneal injection of rat/human corticotropin-releasing factor (CRF) (40 micrograms/kg/0.2 ml of saline) resulted in a dramatic increase in specific iodine-125-labeled human interleukin-1 alpha ([125I]IL-1 alpha) binding in the male C57BL/6 mouse pituitary at 2 and 6 h after the injection although it did not affect [125I]IL-1 alpha binding in the mouse hippocampus, spleen and testis at any time after the injection. [125I]IL-1 alpha binding was unchanged at 2 h following dexamethasone (DEX) treatment (1 mg/kg/0.2 ml of 4% ethanol-saline) in the mouse pituitary and the hippocampus. In contrast, DEX inhibited CRF-induced upregulation of IL-1 receptors in the pituitary at 2 h after the injection. These data demonstrate complex interactions between CRF and DEX on IL-1 receptors during stress.

Interleukin-1-induced calcium flux in human fibroblasts is mediated through focal adhesions

Interleukin-1 (IL-1) is an important mediator of inflammation and also modulates fibroblast metabolism. To assess mechanisms of IL-1-induced signal transduction and calcium flux, early passage human fibroblasts were loaded with fura2/AM. Cells grown on coverslips exhibited dose-dependent [Ca2+]i responses that were maximal at 10(-8) M IL-1 beta with time to maximum flux of 50 s. Cells incubated with anti-Type 1-IL-1 receptor antibody exhibited a 45 nM increase in [Ca2+]i above baseline but demonstrated no calcium response after IL-1 beta treatment. Incubation with EGTA (5 mM) or thapsigargin (1 microM) caused 75% and 37% reductions, respectively, in the IL-1-induced [Ca2+]i increase, suggesting that extracellular Ca2+ predominates in IL-1-stimulated calcium flux. Cells in suspension did not exhibit [Ca2+]i responses to IL-1 beta. The relationship between [Ca2+]i signaling and focal adhesions was examined by plating cells on fibronectin or poly-L-lysine, conditions that either permitted or blocked the formation of focal adhesions. Cells on fibronectin exhibited co-distribution of immunostaining for talin, vinculin, IL-1 receptor, and focal adhesion kinase (pp125fak) in focal adhesions and demonstrated [Ca2+]i responses with 10(-8) M IL-1 beta. Cells on poly-L-lysine or cells in suspension did not exhibit co-distribution of pp125fak, IL-1 receptor, and focal adhesion proteins and did not exhibit calcium flux. The dependence of IL-1-stimulated [Ca2+]i responses on tyrosine kinases was examined first by treating cells with genistein, a selective inhibitor of tyrosine kinases. Genistein (100 microM) completely blocked [Ca2+]i responses to 10(-8) M IL-1, whereas its inactive analogue genistin was not inhibitory. Second, fibroblasts lysates were immunoprecipitated with an antiphosphotyrosine antibody and the lysates were Western-blotted with an anti-pp125fak antibody. Cells grown on fibronectin and stimulated with IL-1 exhibited tyrosine phosphorylation of pp125fak whereas untreated cells or cells grown on poly-L-lysine and treated with IL-1 showed no reaction. Fibroblasts electroinjected with anti-pp125fak monoclonal antibody showed no [Ca2+], response, whereas cells treated with an irrelevant antibody exhibited a normal [Ca2+]i response. Collectively, these data indicate that fibroblasts require substrate attachment and clustering of IL-1 receptors to focal adhesions for IL-1-induced [Ca2+]i responses. Calcium fluxes are mediated through tyrosine kinases whose substrates include pp125fak. These studies therefore demonstrate that activation of intracellular signaling pathways by IL-1 is dependent on IL-1 receptor-cytoskeletal protein interactions.

Interleukin-1 and its inhibitors: implications for disease biology and therapy

IL-1 alpha and IL-1 beta are polypeptide hormones that exhibit a broad spectrum of beneficial and harmful biologic activities. Clinical trials designed to benefit from its stimulatory effects on human hematopoiesis and from its role in improving host defenses, are being currently conducted. Other in vivo studies, using IL-1 inhibitors with an attempts to block the detrimental effects of IL-1, are underway. Because of the multifunctional effects of IL-1 in human physiology and its pathogenetic role in several diseases, the capability to control the effects of IL-1 may prove to be a useful tool in medical practice.

Cytokine measurements and interpretation of cytokine assays in human disease

Cytokines are powerful mediator and communication molecules capable of regulating a wide spectrum of biologic functions, including immune responses. Although the role of cytokines in the pathogenesis of human disease is not yet understood, assays for cytokines have become a common feature in research and clinical laboratories. However, numerous pitfalls accompany measurements of cytokine levels in body fluids and of cytokine synthesis or gene expression in tissue. Interpretation of results obtained in cytokine assays, especially those performed with pathologic specimens, is fraught with difficulties. While cytokine assays are clearly of value in monitoring patients treated with recombinant cytokines or receiving anticytokine therapy, the clinical significance of cytokine assays is not yet fully established. In this review, some of the complexities associated with cytokine monitoring are discussed. The crucial importance of understanding cytokine biology for meaningful assay interpretation is emphasized.

Reciprocal modulation of corticotropin-releasing factor and interleukin-1 receptors following ether-laparotomy stress in the mouse

Ether-laparotomy stress resulted in a dramatic decrease in specific iodine-125-labeled ovine CRF binding ([125I]oCRF) in the pituitary at 6 h after the onset of the stress although it did not affect [125I]oCRF binding in the pituitary at 2 h after the stress. [125I]oCRF binding was unchanged in the frontal cortex after the stress. In contrast, [125I]interleukin-1 (IL-1)alpha binding was significantly increased in the pituitary at 2 h after the stress and tended to be higher than non-stressed levels at 6 h after the stress but was not statistically significant. Ether-laparotomy stress did not affect [125I]IL-1 alpha binding in hippocampus, spleen and testis at any time after the stress. Plasma adrenocorticotropic hormone (ACTH) and corticosterone were increased at 2 h after the stress. These data demonstrate complex interactions between CRF and IL-1 receptors on HPA axis during stress.

Species-specific binding of IL-1, but not the IL-1 receptor antagonist, by fibroblasts

Our laboratory previously reported that bovine thymocytes and fibroblasts proliferated only in response to bovine IL-1, whereas proliferation of murine thymocytes was augmented equally well by murine, human, and bovine IL-1. In this study, we used direct and competitive receptor binding assays to determine whether differential binding of homologous versus heterologous IL-1 accounts for the species-specific response of bovine fibroblasts. Our results demonstrated that bovine and human fibroblasts bound homologous IL-1 with high affinity and heterologous IL-1 with lower affinity. In contrast, murine fibroblasts bound both homologous and heterologous IL-1 with high affinity. Because IL-1 and the human IL-1 receptor antagonist (IL-1ra) both bind to type 1 IL-1 receptors, we also determined whether the IL-1ra demonstrated receptor binding properties similar to human IL-1 for bovine, human, and murine fibroblasts. To our surprise, the human IL-1ra bound equally well to bovine, human and murine fibroblasts. We used this characteristic of the IL-ra to perform affinity cross-linking analysis of the IL-1 receptors on bovine, human and murine fibroblasts. These comparisons demonstrated the IL-1 receptors on bovine and human fibroblasts have similar molecular sizes (M(r) 73 kDa and M(r) kDa, respectively), whereas, IL-1 receptors on murine fibroblasts have an estimated molecular size of M(r) 88 kDa. These data demonstrate that IL-1 receptors on bovine fibroblasts preferentially bind homologous IL-1, but bovine fibroblasts do not discriminate binding by the human IL-1ra. In contrast, murine fibroblast IL-1 receptors bind heterologous IL-1 with high affinity.

Receptor mediated endocytosis and intracellular fate of interleukin 1

We have studied the receptor mediated endocytosis of interleukin 1 (IL1) by the murine thymoma cell line EL4. These cells express the Type I IL1 receptor which binds its ligand with both high (Kd = 65 pM) and low affinity (Kd = 14.5 nM). We have shown that the two affinity states of the receptor have different rates of turnover both in the absence and presence of ligand. The biological responses of cells to IL1 stimulation are rapid and occur at low levels of receptor occupancy, whereas receptor mediated endocytosis of IL1 is relatively slow. Internalized IL1 appears to accumulate within cells in a non-degraded form and a proportion of this is associated with a detergent insoluble intracellular fraction, which may reflect transport to the nucleus. In this article, we review our previous findings and discuss the possible biological significance of IL1 internalization and nuclear targeting.

Acridinium ester labelled cytokines: receptor binding studies with human interleukin-1 alpha, interleukin-1 beta and interferon-gamma

As a consequence of environmental protection and legal restrictions, increasing efforts are made to avoid radioactivity. One alternative is the labelling of ligands with chemiluminescent acridinium esters such as 2,6-dimethyl-4-(N-succinimidyloxy-carbonyl)phenyl 10-methylacridinium-9-carboxylate methosulphate (DMAE-NHS). When exposed to hydrogen peroxide in a basic solution, the DMAE-moiety decays with emission of a short-lasting chemiluminescent flash. With the goal of replacing the radioactive label in protein ligands with a DMAE label, and of increasing the efficiency by using microtitre plate technology for DMAE detection, we compared the receptor binding properties of iodinated interleukin-1 alpha (125I-IL-1 alpha), interleukin-1 beta (125I-IL-1 beta) and interferon-gamma (125I-IFN-gamma) with the corresponding DMAE-labelled ligands. The luminescence signal was assessed in a single-tube luminometer and in the prototype of a chemiluminescent microtitre plate reader. Derivatization of the three proteins with DMAE-N-hydroxy-succinimide resulted in photon yields of up to 100,000 counts per femtomole. As shown by Scatchard analysis, no significant loss of receptor binding affinity was observed, which might have been expected as a consequence of the chemical modification of the proteins. The use of DMAE labelling of proteins has the following advantages as compared to iodination: (i) the coupling reaction and binding assay can be performed in a normal laboratory, (ii) since there is no radiolysis, the DMAE-labelled proteins remain stable, (iii) the detection sensitivity may be improved as a consequence of higher specific activity of the DMAE label.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of growth factors in cutaneous wound healing: a review

The well-orchestrated, complex series of events resulting in the repair of cutaneous wounds are, at least in part, regulated by polypeptide growth factors. This review provides a detailed overview of the known functions, interactions, and mechanisms of action of growth factors in the context of the overall repair process in cutaneous wounds. An overview of the cellular and molecular events involved in soft tissue repair is initially presented, followed by a review of widely studied growth factors and a discussion of commonly utilized preclinical animal models. The article concludes with a summary of the preliminary results from human clinical trials evaluating the effects of growth factors in the healing of chronic skin ulcers. Throughout, the interactions among the growth factors in the wound-healing process are emphasized.

Mathematical modeling of T-cell proliferation

A mathematical model of the T-lymphocyte proliferation process (in vivo and in vitro) is presented. This model takes into account cell-cycle progression and the regulation by lymphokines (lymphocyte activating factor interleukin 1 and T-cell growth factor interleukin 2). Using data on the generalized picture of the short-term course of viral hepatitis B, the parameter estimation procedure is carried out. The possibility of immunocorrection (by means of injection of a pharmacologic dose of IL-2) during the immune response to viral hepatitis B with T-lymphocyte deficiency is shown.

Identification of a specific receptor for interleukin-1 in vascular smooth muscle cells: regulation by interleukin-1 and interleukin-6

A fluorescently labeled ligand was utilized to establish the existence of an interleukin-1 (IL-1) receptor in vascular smooth muscle. The binding of the phycoerythrin-labeled IL-1 beta to the murine T cell line, EL-4, was examined as a positive control. The phycoerythrin-labeled IL-1 beta identified a specific IL-1 receptor in the EL-4 cells. Vascular smooth muscle cells were also positively stained by the fluorescent ligand. The binding of phycoerythrin-labeled IL-1 beta to these cells was saturable and reversed by 100-fold excess unlabeled IL-1 beta. Incubation of the vascular smooth muscle cells with IL-1 beta (25 ng/ml) or IL-6 (250 ng/ml) for 18 h increased and decreased, respectively, the percentage of cells positively stained by phycoerythrin-labeled IL-1 beta which suggests these cytokines regulate IL-1 receptor expression in these cells. These data indicate a specific receptor for IL-1 exists in vascular smooth muscle cells.

Characterization and identification of interleukin-1 receptors on bovine fibroblasts

Interleukin-1 (IL-1), a pro-inflammatory cytokine, initiates its many biological effects by first binding to cell-surface receptors. Prior to this study, there were no published reports addressing the nature of the bovine IL-1 receptor. In this study, we characterized and identified cell-surface IL-1 receptors on bovine fibroblasts. Direct binding studies using [125I]-labeled bovine IL-1 beta demonstrated that bovine fibroblasts had approximately 130 high affinity and 2,500 low affinity binding sites (Kd = 4.9 x 10(-11) M and 3.7 x 10(-9) M, respectively). Competitive binding studies using unlabeled recombinant bovine IL-1 beta, IL-2, IFN-alpha, and bovine insulin demonstrated that only unlabeled bovine IL-1 beta competitively blocked fibroblast binding of [125I]-labeled bovine IL-1 beta. Affinity cross-linking of [125I]-labeled IL-1 beta to fibroblasts demonstrated that IL-1 receptors on bovine fibroblasts have an apparent M(r) of 71.5 kD. This report provides the first characterization and identification of IL-1 receptors on bovine fibroblasts.

Heterogeneity of type-II interleukin-1 receptors. Heterogeneity of B-cell interleukin-1 binding created by dimerization of type-II interleukin-1 receptors

The binding of IL-1 alpha and IL-1 beta to two human lymphoblastoid B-cell lines, Raji and RPMI 1788, was compared with binding to the murine T-cell line, EL4. Dramatic differences in IL-1 binding were observed. Both human B-cell lines bound much less IL-1 alpha than IL-1 beta, expressed 5-10 times more receptors per cell for IL-1 beta than did the EL4 cell line, and demonstrated a large difference in the ability of IL-1 alpha to compete with IL-1 beta for binding. The B-cell lines demonstrated a low number of high-affinity IL-1 alpha receptors and a large number of IL-1 alpha receptors with a much lower affinity. Inhibition studies demonstrated that only IL-1 beta could compete for the binding of radiolabeled IL-1 beta to the B-cell IL-1R. Furthermore, SDS-PAGE analyses of lysates of the B-cell lines that had been affinity cross-linked with 125I-IL-1 alpha revealed two bands corresponding to IL-1R structures of 60 and 110 kD. These results coupled with a nonequilibrium binding study suggested a dimerization of a common type-II IL-1R polypeptide, the dimer being responsible for the high-affinity IL-1 alpha-binding site of the B-cell lines.

Receptor binding and biological activity of IL-1 alpha, IL-1 beta, IL-1 beta analogues and an IL-1 antagonist in A375 human melanoma cells

A receptor binding assay for IL-1 peptides on human melanoma cells of the A 375 cell line is reported. Strains differing in their sensitivity to the cytotoxic effects of IL-1 beta were compared. In both strains, binding equilibrium at temperatures between 0 degrees and 37 degrees C was reached after 4 to 8 hours. At 37 degrees C, most of the bound ligand was rapidly internalized leaving a constant level of surface receptors. Scatchard analysis at 0 degrees C revealed a single class of high affinity receptors with a similar KD in both IL-1 resistant (0.18 +/- 0.07 nM) and sensitive strains (0.14 +/- 0.06 nM) but a 10-fold difference in the number of binding sites. Whereas > 1000 binding sites per cell were regularly observed in all resistant strains, only 100-200 sites could be detected on the IL-1 sensitive cells. In displacement assays, IL-1 beta was found to be slightly more potent than IL-1 alpha in both strains. In an attempt to further characterize the IL-1 binding site in these cells, the binding characteristics and biological activity of 20 point mutations of IL-1 beta were examined. EC50 values similar to those of the wild type peptide were found in all these analogues with the exception R11S and E128K: their EC50 was increased by a factor of 10 but the biological activity was reduced 1000-fold as compared to IL-1 beta. The relative potency of an IL-1 receptor antagonist was similar to that of IL-1 beta in the displacement binding assay but a 100-fold higher concentration was required to completely block the cytotoxic effects of IL-1 beta. These results show that A375 human melanoma cells are useful for screening the binding and biological properties of analogues of the IL-1 family of peptides.

Expression and biological activity of interleukin-1 receptors in mouse gamma/delta thymocytes during ontogeny

We have recently shown that the response of mouse thymocytes to interleukin (IL)-1 + IL-2 was maximal at birth and that the responding cells displayed a CD4-CD8- T cell receptor (TcR) gamma/delta + phenotype. Unexpectedly, despite their high proportion of gamma/delta + cells, fetal thymocyte populations responded only weakly to IL-1 + IL-2. In this report, we demonstrate that the discrepancy between the day 17.5 fetal and newborn sensitivities to the combined action of IL-1 and IL-2 is a consequence of the different patterns of high-affinity IL-1 receptor (IL-1R) expression displayed by these two cell subsets. Actually, high- and low-affinity IL-1R are found in TcR gamma/delta + newborn cells and, in contrast, only low-affinity IL-1R are detectable in day 17.5 fetal cells. Our binding and functional studies strongly support the hypothesis that high-affinity IL-1R on the one hand, and low-affinity ones on the other hand, are involved in the response to IL-1 + IL-2 of newborn and day 17.5 fetal thymocytes, respectively. In addition, the high-affinity IL-1R appear to be far more efficient than the low-affinity receptors in promoting IL-2 responsiveness of thymocytes.

Selective regulation of beta 2-adrenergic receptor gene expression by interleukin-1 in cultured human lung tumor cells

The regulation of beta 1- and beta 2-adrenergic receptors (beta 1AR and beta 2AR) and receptor gene expression by interleukin-1 alpha (IL-1 alpha) was studied in cultured A549 human lung adenocarcinoma cells. The density and affinity of beta 1 AR and beta 2 AR were analyzed by computerized curve fitting of 125I-pindolol binding and its displacement by subtype selective antagonists. Steady state levels of receptor mRNAs were quantified by DNA excess solution hybridization assays. A549 cells in preconfluent cultures had fewer beta 1AR than beta 2AR (beta 1: 1.9 +/- 0.3 vs beta 2: 4.0 +/- 0.5 fmol/mg protein, means +/- SE), but lost most of their beta 2 AR upon reaching confluency (beta 1: 2.7 +/- 0.4, beta 2: 0.8 +/- 0.3 fmol/mg). Incubation of preconfluent cells for 24 hr with 20 pM of human recombinant IL-1 alpha did not modify the density of either of the beta AR subtypes. Similar incubations of confluent cells increased the density of beta 2 AR from 0.8 +/- 0.3 to 4.2 +/- 0.9 fmol/mg, while the density of beta 1 AR and the antagonist affinities of both receptors remained unaltered. The IL-1 alpha-induced increase in beta 2 AR density in confluent cells was antagonized in a concentration-dependent manner by a recombinant protein antagonist of type I IL-1 receptors (IC50: 0.2 nM). The IL-1 alpha-induced increase in beta 2AR density was preceded by an increase in the steady state level of beta 2AR mRNA, while levels of beta 1AR mRNA remained unchanged. IL-1 alpha increased the stability as well as the rate of transcription of beta 2AR mRNA. These findings demonstrate for the first time that activation of type I IL-1 receptors in A549 cells leads to a cell density-dependent, selective upregulation of beta 2AR, and that the mechanism of this effect involves increased formation and stability of the beta 2AR message.

Native cytokine antagonists

Cytokines orchestrate the complex homeostasis of cells and tissues by acting in both an autocrine and paracrine fashion. The processes responsible for regulation of cytokines is not well understood. This chapter has summarized what is known about antagonism and inhibition of the action of cytokines. Several concepts have emerged from work in this area. At least two cytokines (IL-1 alpha and IL-1 beta) have an endogenous receptor antagonist, the IL-1 receptor antagonist. This is the first example of one endogenous molecule directly blocking the binding of another molecule to its receptor: most forms of regulation occur through independent receptors. Several cytokines, including TNF, IFN-gamma, IL-2 and IL-4, are inhibited by soluble receptors. Several cytokines, including IL-10, TGF-beta and MDF, act to inhibit other cytokines. It is likely that these inhibitors will be found to have pleiotropic actions in vivo. Finally, we describe antibody inhibition of cytokines. Detailed studies will be required to understand the complex interplay of the aforementioned cytokine inhibitors and the processes they regulate.

Non-specific binding of normal human IgG, including F(ab')2 and Fc fragments, to embryonic rat brain neurons and human cortex synaptosomes

Binding of normal human IgG to embryonic rat brain neurons was quantitated by flow cytometry. IgG binding was linear between 0.05 and 1.5 mg/ml; slight binding was detectable even at normal cerebrospinal fluid concentrations. Similar binding curves were obtained for purified Fc and F(ab')2 fragments from normal human IgG. Normal human IgG also bound to synaptosomes (resealed nerve terminals) from human cerebral cortex. However, competition assays utilizing 125I-IgG showed no evidence for specific binding. This study indicates that the specificity of putative anti-neuronal antibodies should be confirmed by competition assays as for other receptor-ligand binding.