Native interleukin 1 inhibitors

Expression of Interleukin-1 and Interleukin-1 Receptors Type 1 and Type 2 in Hodgkin Lymphoma

Signaling through the IL-1-receptor type 1 (IL-1R1), IL-1 is required for initiation and maintenance of diverse activities of the immune system. A second receptor, IL-1R2, blocks IL-1 signal transduction. We studied expression of IL-1beta, IL-1R1, and IL-1R2 in 17 Hodgkin lymphomas (HL) by in situ hybridization (ISH). IL-1beta expressing cells, morphologically consistent with endothelial cells and fibroblasts, occurred in all HL tissues with elevated transcript levels in areas of active fibrosis. Hodgkin and Reed-Sternberg (HRS) cells of all cases expressed low IL-1R1 transcript levels in some tumor cells, and high levels of IL-1R2 in large proportions of HRS cells. Only few bystander cells showed low levels of IL-1R1 and IL-1R2 RNA. Supernatants of 4 out of 7 HL-derived cell lines contained soluble IL-1R2 protein at high levels. HL patient sera carried variably amounts of IL-1R2 protein with significantly increased titers in patients with active disease compared to patients in complete remission and control individuals without HL. Western blots and co-immunoprecipitations showed binding of the IL-1R2 to the intracellular IL-1R-accessory protein (IL-1IRAcP). These data suggest functions of the IL-1R2 as a „decoy-receptor” sequestrating paracrine IL-1 extracellularly and intracellularly by engaging IL-1IRAcP, thus depriving IL1-R1 molecules of their extracellular and intracellular ligands. Expression of IL1-R2 by HRS cells seems to contribute to local and systemic modulation of immune function in HL.

A primer in cytokines

The host response to injury or infection is a complex interplay of endocrine, metabolic, and immunological alterations designed to promote wound healing and restore the system to a state of homeostasis. Cytokines are the primary mediators of the inflammatory response to injury. This article serves as an introduction to this important class of inflammatory mediators. The major pro- and anti-inflammatory cytokines as well as the chemokines are discussed. Results from laboratory and clinical attempts at manipulation of these mediators are discussed and recommendations for future research in anticytokine therapy are made.

Abnormal interleukin-1 receptor type II gene expression in the endometrium of women with endometriosis

Interleukin 1 (IL-1) is a major proinflammatory cytokine that is believed to play a central role in the pathophysiology of endometriosis. The IL-1 receptor type II (IL-1RII) is known to bind to IL-1 and to inhibit its biological effects. In our previous studies, we showed that human endometrium expresses IL-1RII, and we observed reduced expression of the protein in women with endometriosis. The aim of this study was to investigate IL-1RII mRNA in the endometrial tissue of normal women (n = 26) and of patients with various degrees of endometriosis (n = 53). In situ hybridization showed that IL-1RII mRNA expression was significantly decreased in endometriosis, particularly during the early stages of the disease (stages I and II). This was quite obvious in both glandular and stromal cells, and it was corroborated by reverse transcription-polymerase chain reaction analysis of IL-1RII mRNA in the endometrial tissue of women with (n = 10) and without (n = 8) endometriosis. The reduced levels of IL-1RII mRNA in the endometrium of women suffering from endometriosis reveals a profound defect in IL-1RII gene expression and, consequently, a reduced capability of endometrial tissue to down-regulate IL-1 activity. Defective IL-1RII gene expression during the early stages of endometriosis (stages I and II) may contribute to the etiology of the disease.

Autologous serum deprivation restored IL-1 receptor antagonist production by peripheral blood mononuclear cells in patients with gastric cancer

It has been established that cancer patients have immunosuppressive substances in their sera that depress cellular immunity. Although plasma exchanges have been attempted to remove these substances and to improve immunity to cancer, little is known about its mechanism from the viewpoint of cytokine pattern. The levels of the cytokines, tumour necrosis factor-alpha, interleukin 1beta, interleukin 6, interferon-gamma and interleukin-1 receptor antagonist (IL-1ra) by peripheral blood mononuclear cells (PBMC) were determined simultaneously by the whole-blood assay and the PBMC assay in 20 patients with gastric cancer and in 10 healthy volunteers. In both assays the cytokine levels were lower in patients with cancer compared with healthy controls, with the exception of IL-1ra. In the PBMC assay, the IL-1ra level in cancer patients was significantly higher than that in controls. No statistical correlation between the cytokine levels determined by the two assays was found. We suggest that autologous serum deprivation restored and enhanced IL-1ra production, and normalized the cytokine cascade in immune response, in patients with gastric cancer.

Immunohistochemical evaluation of interface membranes from failed cemented and uncemented acetabular components

Aseptic loosening of acetabular components is a primary factor compromising the long-term outcome of cemented and cementless total hip replacement. It is unknown whether the pathogenesis of the loosening process is identical for both types of fixation. The specific aim of this study was to determine whether there is a difference in the cellular and cytokine profiles of interface membranes removed from between the implant and the host bone from failed cemented (n = 5) and failed cementless acetabulae (n = 5). Routine histology and immunohistochemical evaluations were completed on each tissue specimen. The monoclonal antibodies used included those specific for cell types (macrophages, fibroblasts, T lymphocytes) and for cytokines (IL-1beta, IL-6, TNF-alpha). The patients were all revised for loosening. The time to revision was significantly longer for the cemented group (16.6 yr; 13-21 range) than for the cementless group (8.9 yr; 4-13 range). In all cases, slides from each group stained positively for each of the cell types and cytokines evaluated. Immunohistochemical analyses indicated a predominance of macrophages and ubiquitous staining for the cytokines IL-1beta and TNF-alpha within the membranes of both patient groups. The intensities of cytokine staining were similar for both patient groups. More regions of fibroblastic connective tissue were observed surrounding failed cementless components as compared to those of the cemented group. The clinical ramification of our findings is that, despite differences in the cellular composition of the periprosthetic membranes, the membranes from failed cemented and cementless implants contain cytokines, which have been shown to be capable of modulating the inflammatory response. These inflammatory mediators are likely to play a significant role in the development of osteolysis and prosthetic loosening.

Balance of interleukin-1 beta and interleukin-1 receptor antagonist in human periapical lesions

Interleukin-1 beta (IL-1 beta) has been considered as a major potent mediator of bone resorption and implicated in the development of human periapical lesions. Among naturally occurring interleukin-1 (IL-1) inhibitors, IL-1 receptor antagonist (IL-1ra) is a 22 kDa protein that shares homology with IL-1 beta and IL-1 alpha, binds to IL-1 receptor with similar affinity to IL-1, and has no known agonist properties. In this study, we measured the periapical exudate (PE) levels of IL-1 beta and IL-1ra from human periapical lesions. PE samples were collected from root canals during routine endodontic treatments, and the enzyme-linked immunosorbent assay was used to measure PE-IL-1 beta and IL-1ra. Detectable levels of both IL-1 beta and IL-1ra were found in 25 of 29 clinical samples. Relatively high levels of IL-1ra compared with IL-1 beta (mean IL-1ra:IL-1 beta ratio = 128:7; range: 0.9 to 495.4), and significantly positive correlation between IL-1ra and IL-1 beta levels was found. The PE-IL-1ra:IL-1 beta ratios obtained from symptomatic lesions were significantly lower than those from asymptomatic lesions. These results suggest that IL-1ra-mediated IL-1 antagonism occurred to block locally produced IL-1 activity, and the balance of IL-1 to IL-1ra production may be crucial in the development of periapical lesions.

Gingival crevicular interleukin-1 and interleukin-1 receptor antagonist levels in periodontally healthy and diseased sites

Interleukin-1 (IL-1) molecules, IL-1 alpha and IL-1 beta are cytokines involved in the acute-phase response against infection and in the pathogenesis of periodontal destruction. Administration of exogenous IL-1 receptor antagonist (IL-1ra) is effective in reducing the inflammatory reactions mediated by IL-1. However, the relationship between these three naturally occurring IL-1 molecules and periodontal diseases has been poorly characterized. We investigated the correlation of gingival crevicular IL-1 molecules and the clinical status of patients with different severities of periodontitis. IL-1 alpha, IL-1 beta, IL-1ra and the total IL-1/IL-1ra ratio (IL-1 activity index; IL-1AI) were measured in 75 gingival crevicular fluid (GCF) samples from non-inflamed gingiva sites in 2 healthy subjects and diseased sites in 7 patients with several types of periodontitis. IL-1 alpha, IL-1 beta and IL-1ra were measured by specific non-cross-reactive enzyme linked immunosorbent assay. The probing depth, gingival index and alveolar bone loss of each site was recorded at the time of GCF sampling. The total amount of IL-1 alpha, IL-1 beta and the IL-1AI, but not total IL-1ra, were found to be correlated with alveolar bone loss score. Three IL-1 molecules were also measured in the gingival tissue of patients with periodontitis. A similar progressive decrease of the IL-1AI was detected in gingival tissue with periodontitis. These results suggest that the amounts of both crevicular IL-1 and IL-1AI are closely associated with periodontal disease severity.

Autocrine interleukin-1 receptor antagonist can support malignant growth of glioblastoma by blocking growth-inhibiting autocrine loop of interleukin-1

In situ hybridization (ISH) of human glioblastoma tissue sections revealed expression of interleukin-1 (IL-1)alpha and/or beta and IL-1 receptor types I and II (IL-1R I and II) in the majority of cases evaluable. To understand the function of IL-1-family members in human glioblastomas, we have studied 6 glioblastoma cell lines. RT-PCR, ISH, ELISA and 125I-IL-1-binding assays revealed expression of IL-1 and high-affinity receptors for human (h)IL-1 in all but 1 cell line. Using a colony growth assay in semi-solid media for testing serial plating efficacy (PE, number of colonies per number of cells seeded in %), only the IL-1R-negative cell line was not influenced by recombinant human (rh)IL-1alpha or -beta, whereas IL-1 down-regulated the self-renewal of clonogenic cells of the other glioblastomas. Tritiated thymidine uptake was down-regulated by rhIL-1 in all cell lines studied. Cell viability remained unchanged by rhIL-1. Wherever growth modulation by rhIL-1 was detected, it could be reversed by either soluble IL-1R I or II or by rhIL-1 receptor antagonist (ra). IL-1ra not only was able to reverse rhIL-1-induced growth modulation but alone could modulate glioblastoma growth in comparison with control in cell lines producing IL-1. Our results show the presence of public autocrine loops for IL-1 leading to growth inhibition in some glioblastomas. To understand these loops, we have studied expression and function of IL-1ra in glioblastomas. ISH of human glioblastoma tissue sections revealed expression of hIL-1ra in all 8 cases evaluable. In 4 of 6 cell lines, IL-1ra was found in the supernatant under constitutive conditions, the IL-1R-negative line being among the 2 non-producers. The other non-producing cell line, HTB 17, showed expression of hIL-1R II. Most interestingly, a neutralizing antibody against IL-1ra down-regulated growth of IL-1- and IL-1ra-producing glioblastoma cells to approx. 30% of the controls. Thus, public autocrine loops for IL-1 in human glioblastomas exist and result in growth inhibition. An autocrine production of IL-1-antagonizing molecules such as IL-1ra by these tumors can counteract this IL-1 function and represent a basic escape mechanism supporting malignant growth in some glioblastomas.

Interleukin-1 receptor antagonists and other markers in colorectal cancer patients

BACKGROUND

Although the interleukin-1 receptor antagonist (IL-1ra) has been suggested as a potentially valuable therapeutic agent and has been shown to improve outcome in various animal models of arthritis, septic shock, and inflammatory bowel disease, there is little information available about its level in the circulation in patients with cancer.

METHODS

Serum levels of IL-1ra, soluble interleukin-2 receptor (sIL-2r), soluble intercellular adhesion molecule-1 (sICAM-1), and cortisol were measured in normal controls and patients with colorectal cancer.

RESULTS

The data showed that serum IL-1ra levels in patients were significantly lower than those of healthy controls (P < 0.05). In contrast, serum sIL-2r and cortisol levels in patients were significantly higher than those of normal controls (P < 0.01). Serum sICAM-1 levels in patients were the same as in normal controls.

CONCLUSIONS

These results suggested that a reduced level of IL-1ra exists in colorectal cancer patients relative to normal controls, indicating that cancer patients have an immunologic disorder and that exogenous IL-1ra administration might be a future alternative for cancer treatment.

Comparative effects of lipopolysaccharide on newborn versus adult rat hepatocyte and nonparenchymal cell cocultures

OBJECTIVE

To examine the effects of development on the response of hepatocytes and nonparenchymal cells to an endotoxin challenge as an in vitro model of organ system dysfunction at differing developmental ages.

DESIGN

In vitro animal cell culture model.

SETTING

University teaching hospital research laboratory.

SUBJECTS

Adult and newborn Sprague-Dawley rats.

INTERVENTIONS

The method of hepatocyte and nonparenchymal cell coculture was utilized and modified to allow evaluation of cells derived from newborns. Cells were isolated from adult rats by standard perfusion technique. Hepatocytes and nonparenchymal cells were isolated from newborn rats by use of identical enzymatic degradation after fine mincing of the organ. Isolated cells were purified by density gradient. The hepatocytes were incubated in standard cell culture plates for 24 hrs before the addition of nonparenchymal cells. Hepatocytes were incubated with similar-age nonparenchymal cells. After an additional 24 hrs, serial log dilutions of lipopolysaccharide were added as a stimulus and the system was cultured an additional 24 hrs. The response of the hepatocytes was assessed by determination of 3H-leucine incorporation in acid-precipitated protein. In addition, the production of tumor necrosis factor, interleukin (IL)-1, and IL-6 by isolated nonparenchymal cells from adult and newborn rats was determined after stimulation with serial log dilutions of lipopolysaccharide by bioassay.

MEASUREMENTS AND MAIN RESULTS

Both adult and newborn hepatocytes cocultivated with nonparenchymal cells demonstrated a comparable and statistically significant dose response to lipopolysaccharide (p < .01). The newborn hepatocytes demonstrated a greater rate of protein synthesis than the adult hepatocytes at all concentrations of lipopolysaccharide. Tumor necrosis factor production by newborn and adult nonparenchymal cells was similar at all lipopolysaccharide doses. IL-1 production demonstrated a positive dose response to lipopolysaccharide in the adult and newborn nonparenchymal cells, with a trend (p = .17) toward greater IL-1 secretion by the adult cells. There were significant differences in IL-6 production by isolated nonparenchymal cells at lipopolysaccharide doses of 0.01, 0.1, and 10 micrograms/mL. While a similar trend was apparent in the cocultured cells, the significance was not apparent, except at the highest lipopolysaccharide dose.

CONCLUSIONS

The dose responses of newborn and adult hepatocytes to nonparenchymal cells stimulated with lipopolysaccharide were similar, although newborn hepatocytes appeared to have an inherently higher rate of protein synthesis compared with adult hepatocytes. Cytokine production was similar in nonparenchymal cells of both ages, although IL-1 production by stimulated newborn nonparenchymal cells appeared to be less than IL-1 production by adult nonparenchymal cells.

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.

Cytokine inhibitors in autoimmune disease

The cytokine network participates in the modulation of the immune system. Furthermore, the formation of the cytokine-receptor complex, as well as the transcription, translation, secretion, or degradation of cytokines interfere with the functions of cytokines. Cytokine inhibitors include antagonists, soluble receptors, cytokine-binding proteins, and cytokines that block other cytokines. In autoimmune diseases, an abnormal production of proinflammatory cytokines, or a reduced inhibition of their actions, may lead to an imbalance. The main cytokine inhibitors include interleukin-1 receptor antagonist (IL-1ra), soluble IL-1 receptor (sIL-1R), soluble TNF-alpha receptors (soluble TNF-Rs), and certain cytokines, such as IL-4, TGF beta, and IL-10. The combination of cytokine inhibitors is a potential therapeutic approach in the treatment of immunoinflammatory diseases. The nonspecific effects of immunosuppressive drugs are improved by using inhibitors with more specific actions on the functions of proinflammatory cytokines.

Interleukin-1 receptor antagonist and interleukin-4 in gingival crevicular fluid of patients with inflammatory periodontal disease

Interleukin-1 receptor antagonist (IL-1ra) and interleukin-4 (IL-4) were detected in gingival crevicular fluid (GCF) by an immunochemical method. However, we could not detect IL-4 in GCF from severe inflammation sites. In addition, we sought to detect which cells had produced cytokines in moderately inflamed gingival tissues by means of immunohistochemistry. The cell types expressing CD 68 were identified as monocytes/macrophages and stained positively for IL-1ra. The helper T cells identified by immunostaining for CD 4 stained positively for IL-4. These results suggest that IL-4 is one of the mediators regulating the degree of local inflammation in periodontal disease.

Human chorionic gonadotrophin-induced testicular inflammation may be related to increased sensitivity to interleukin-1

Treatment of adult male rats with human chorionic gonadotrophin (hCG) results in an inflammation-like response in the testicular microcirculation. Polymorphonuclear (PMN) leukocytes accumulate in venules and vascular permeability is increased. The mechanism behind this response was studied. Treatment with an interleukin-1 receptor antagonist partly prevented the hCG induced accumulation of PMN leukocytes 4 h after treatment. Human recombinant interleukin-1 alpha (IL-1 alpha) and beta (IL-1 beta), serotonin, and histamine were injected intratesticularly on one side and saline injected on the contralateral side in both intact and hCG-pretreated adult rats. A low dose of IL-alpha (a dose that did not increase vascular permeability in unstimulated testes) increased vascular permeability in the testes of animals treated with hCG 4, 6 or 8 h earlier, but it was without effect in testes from rats treated with hCG 0,1, 2, 16 or 32 h prior to IL-1 injection. The sensitivity to the pro-inflammatory effect of locally injected IL-1 beta was also increased by hCG treatment. There was no increase in vascular permeability after local injection of a large dose of histamine or serotonin in either saline- or in hCG-pretreated animals. Hypothetically, the hCG-induced inflammation-like increase in testicular vascular permeability could be related to increased sensitivity to constitutively produced mediators such as IL-1.

Regulatory effects of endogenous interleukin-1 receptor antagonist protein in immunoglobulin G immune complex-induced lung injury

IL-1 receptor antagonist (IL-1Ra) has regulatory effects on IL-1 activity both in vitro and in vivo. In the IgG immune complex model of lung injury in rats, exogenously administered human IL-1Ra suppressed neutrophil recruitment and ensuing lung injury. In this study, we sought to determine if endogenous rat IL-1Ra might regulate this lung-inflammatory response. By Northern blot analysis of lung mRNA and Western analysis of bronchoalveolar lavage (BAL) fluids, rat IL-1Ra expression was found to increase during development of inflammation in IgG immune complex-mediated alveolitis. By immunostaining, alveolar macrophages and recruited neutrophils were the apparent sources of IL-1Ra. In vivo blocking of endogenous IL-1Ra resulted in a 53% increase in lung vascular permeability and a 180% increase in BAL fluid neutrophils. In companion studies, a significant increase in IL-1beta was found, whereas no significant change in TNF-alpha activity was observed. Whereas the in vivo regulatory effects of IL-1R appear to be limited to IL-1beta, IL-10 regulates both IL-1beta and TNF-alpha in this model, reflected by a 48% increase in BAL IL-1beta in rats treated with anti-IL-10. These findings suggest that IL-1Ra is an intrinsic regulator of inflammatory injury after deposition of IgG immune complexes and that it regulates production of IL-1beta.

Successful eradicating treatment of Helicobacter pylori in patients with chronic gastritis: gastric levels of cytokines, epidermal growth factor and polyamines before and after therapy

In 10 patients with Helicobacter pylori (HP) positive chronic gastritis, gastric mucosal content of interleukin (IL)-1 beta, IL-8, Transforming Growth Factor (TGF)-beta 1, Epidermal Growth Factor (EGF) and Polyamines (putrescine, spermine and spermidine) was evaluated before and after eradicating treatment. Histologically, in all patients eradication of HP was accompanied by a marked reduction of the inflammatory infiltrate. At the same time, at the end of the therapeutical regimen, elevated levels of IL-1 beta, IL-8, TGF-beta 1, putrescine and spermidine/spermine ratio significantly dropped, while EGF mucosal content, significantly increased. Results are discussed in terms of the reciprocal role of inflammatory cytokines, growth factors and polyamines in the evolution of the HP-associated chronic gastritis.

Subcellular localization and characterization of interleukin-1 alpha produced by rat bladder cancer cells

A rat bladder cancer cell line BC31ad, previously reported to constitutively release tumor necrosis factor alpha (TNF alpha), was found to produce an interleukin (IL)-1-like factor inducing proliferation of murine thymocytes in a standard costimulation assay (LAF activity). IL-1-like factor was partially purified by DEAE-Sephacel, Sephacryl S-200 and MonoQ-FPLC chromatographies from the serum-free conditioned medium of a BC31 adderived clone, C19, to the specific activity of 3.2 x 10(6) U/mg and characterized as a protein of molecular weight 17 kDa with isoelectric point 5.2. LAF activity of IL-1-like factor was specifically neutralized with anti-rat IL-1 alpha but not with anti-rat IL-1 beta. These findings show that the IL-1-like factor is rat IL-1 alpha, although the precise molecular relationship with monocyte IL-1 alpha is unclear. Furthermore, IL-1 alpha was shown to be primarily located in the cytosol and plasma membrane without spontaneous release. A kinetics study indicated that it was leaked into the medium late in culture resulting from cell destruction, in contrast to TNF alpha which was released as the cell number was increased. We discussed the possible role of IL-1 alpha as an autocrine or paracrine growth regulator.

The effect of human myelomonocytic leukemic cell line (M20) derived IL-1 inhibitor on human erythroid cell development

The effect of an inhibitor of IL-1, purified from a human myelomonocytic cell line (M20) on the development of human erythroid cell development was studied. The inhibitor, is a protein of 52 kD molecular weight that is distinct immunologically and functionally from other reported IL-1 inhibitors. The experiments were performed in a two-phase culture system that allows separation of the erythroid cell development into an erythropoietin (EPO)-independent phase, where early erythroid-committed BFUe proliferate and differentiate into the more mature progenitors, CFUe, and EPO-dependent phase, where CFUe further proliferate and mature into hemoglobin-containing orthochromatic normoblasts. The results indicated that in both developmental stages the M20-derived inhibitor reversibly blocked cell proliferation without interfering with cell differentiation.

Functional characterization of cytokine autoantibodies in chronic renal failure patients

We have recently reported on an increase of IL-1 alpha and IL-6 autoantibodies in patients maintained on chronic hemodialysis treatment. The aim of the present study was to evaluate functional properties of these autoantibodies. Serum samples of more then 500 chronic renal failure patients with and without replacement therapy were screened for the presence of IL-1 alpha and IL-6 autoantibodies by second antibody precipitation. The neutralizing capacity of IL-1 alpha autoantibody serum was studied by immunofluorescence flow cytometry analysis of IL-1 alpha induced expression of E-selectin (ELAM-1, CD62e) on HUVEC (human umbilical vein endothelial cells). Results of these inhibition studies were confirmed with IgG preparations from antibody positive sera, purified by affinity chromatography. Functional studies on IL-6-dependent B9 cell proliferation were performed with IL-6 autoantibody positive sera, and quantitated with the colorimetric MTT assay. IL-1 alpha induced expression of E-selectin on HUVEC (considered 100% positive cells) was inhibited by each IL-1 alpha autoantibody positive serum sample (N = 13; anti-IL-1 alpha activity: 7.62 to 57.52% binding). Inhibition of E-selectin expression by IL-1 alpha autoantibodies ranged from 0.11 to 80.22% positive cells (0.15 to 92.31% mean fluorescence intensity). A strong correlation of E-selectin expression with IL-1 alpha autoantibody concentration was observed (P < 0.005). Furthermore, IgG eluates from autoantibody positive patients inhibited E-selectin expression to 41.0 +/- 23.1% positive cells if compared with 83.7 +/- 5.7% positive cells of the IgG depleted serum samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Ethanol-induced suppression of interleukin 1-like activity: reversal by a quinone derivative

Chronic ethanol intake impairs several parameters of immune function. Since there is evidence that cytokine production by immune cells may contribute to the immunosuppressive effect of ethanol, we examined interleukin 1 (IL1) production by liver non-parenchymal cells (NPC) in ethanol-fed rats. Male Wistar rats (225-250 g) were fed by continuous intragastric infusion. The source of fat was either saturated fat or polyunsaturated fat. In addition, the effect of a quinone compound on IL1 production was assessed. Animals were fed for various periods: 1 week, 2 weeks, 1 month and 2 months. NPC were isolated and stimulated by lipopolysaccharide. IL1 production by NPC and the ratio of stimulated to unstimulated (S:U) IL1 production were evaluated in the different groups and related to the presence of liver injury. As expected, animals fed corn oil and ethanol (CO+E) developed pathologic liver injury, whereas animals fed saturated fat and ethanol (SF+E) had no liver injury. A progressive decrease in the S:U IL1 ratio was seen in the CO+E group over the 8-week period. The ratio in the SF+E group was higher. The quinone compound reversed the suppressive effect of ethanol on IL1 production. In summary, ethanol-induced suppression of IL1 production was modulated by diet and the presence of liver injury. This suppression of IL1 production was reversed by a quinone compound; the exact mechanism for the reversal of this inhibition is unknown.

Sex- and age-dependency of IgG auto-antibodies against IL-1 alpha in healthy humans

Naturally occurring anti-interleukin (IL)-1 alpha IgG antibodies (Ab-IL-1 alpha) were measured in sera of 466 healthy Danish blood donors. Ab-IL-1 alpha bound IL-1 alpha with exceptionally high affinity (Kd: 10(-11) M) and neutralized both cell-associated and extracellular IL-1 alpha but not IL-1 beta or IL-1 receptor antagonist. More than 80% of the saturable binding of rIL-1 alpha to serum was to Ab-IL-1 alpha, suggesting that these antibodies are the quantitatively most important IL-1 alpha-binding components in serum. Judged by second antibody precipitation assay, the prevalence of Ab-IL-1 alpha varied between 30% and 75% and correlated positively with age (P = 0.037). The binding capacity of serum also increased with age. Although men were more frequently positive than women (P < 0.001), there were no sex- or age-dependent alterations in the average affinities of the antibodies. Free IL-1 alpha-like molecules were generally not detected in these sera. However, acid treatment showed that 25% of Ab-IL-1 alpha-positive sera contained low amounts of IL-1 alpha-Ab-IL-1 alpha immune complexes. IgG4 represented the main IgG isotype, whereas IgG3 Ab-IL-1 alpha were undetectable. The relative amounts of IgG4 Ab-IL-1 alpha increased while IgG2-and IgG1 Ab-IL-1 alpha decreased in elderly individuals. The presence in normal individuals and the lack of affinity maturation with age suggest that Ab-IL-1 alpha may be regulatory natural auto-antibodies perhaps coded by germline genes.

Mouse interleukin-1 receptor antagonist induced by Actinobacillus actinomycetemcomitans lipopolysaccharide blocks the effects of interleukin-1 on bone resorption and osteoclast-like cell formation

We have reported that P388D1 cell line murine macrophages stimulated with lipopolysaccharide (LPS) from Actinobacillus actinomycetemcomitans release interleukin-1 (IL-1) inhibitor. The IL-1 inhibitor was purified from conditioned media of P388D1 cells stimulated with A. actinomycetemcomitans LPS for 72 h to homogeneity by a four-step procedure: acetic acid extraction from conditioned media; Bio-Gel P-60 gel filtration chromatography; DEAE-Sepharose CL-6B column chromatography; and reverse-phase high-performance liquid chromatography on a C18 hydrophobic support. The purified IL-1 inhibitor gave a single band of protein with a molecular mass of 26 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified IL-1 inhibitor was a heat- and acid-stable protein that was inactivated by digestion with trypsin and reduction with dithiothreitol. This inhibitory factor suppressed the proliferation of C3H/HeJ mouse thymocytes and the proliferation of IL-1-dependent cell lines, D10.G4.1 and RPMI 1788, induced by IL-1. However, this inhibitor did not affect the proliferation of IL-2-dependent CTLL-2 cells induced by IL-2, the proliferation of C3H/HeJ mouse thymocytes stimulated with a mitogenic dose of concanavalin A, and the proliferation of IL-6-dependent B9 cells induced by IL-6. Furthermore, the IL-1 inhibitor significantly blocked stimulation of bone resorption in organ cultures of newborn mouse calvaria and inhibited the osteoclast-like cell formation in mouse marrow cultures. A monoclonal antibody prepared against the purified IL-1 inhibitor reacted with mouse recombinant IL-1 receptor antagonist (rIL-1ra), and a polyclonal antibody to mouse rIL-1ra reacted with the IL-1 inhibitor by Western blot (immunoblot) analysis. These results indicate that the IL-1 inhibitor is an identical molecule to rIL-1ra, suggesting that the IL-1 inhibitor (IL-1ra) released by macrophages stimulated with LPS from A. actinomycetemcomitans may play an important mediative role in the development of periodontal disease.

Biology of interleukin-1 (IL-1), with respect to otorhinolaryngology-head and neck surgery

Interleukin-1 (IL-1) has a number of fundamental immunoregulatory, hematologic, metabolic, and physiologic effects and thus is instrumental in the coordination of tissue interactions, such as wound healing, inflammation, and host tumor response. IL-1 stimulates the activation and differentiation of pre-B cells and T cells, chemotaxis of neutrophils, recruitment of bone marrow stem cells, stimulation of arachidonic acid metabolism, degradation of proteoglycans, and increase in basal body temperature. Altered production of IL-1 or IL-1 regulatory factors may have profound clinical consequences, such as seen in AIDS, other viral and malignant diseases, and in uncontrolled inflammatory processes. A variety of positive and negative feedback mechanisms for regulation of IL-1 production have been found; therapeutic interventions are aimed at these regulatory pathways. Through approaches interfering with the signal transduction or processing of IL-1, especially by interleukin-1-receptor antagonists (IL-1RA), future treatment modalities are on the horizon.

In vivo anti-inflammatory effects of the M20 IL-1 inhibitor: II. Effects on serum reactants

We have previously described an IL-1 Inhibitor derived from the M20 myelomoncytic cell line. This line also secretes several molecules of IL-1. We have shown that this factor is specific to IL-1 in vitro, as well as in vivo. In vitro IL-1 induced proliferative responses of mouse thymocytes, human T cells and fibroblasts and IL-1 stimulated PGE2 secretion from fibroblasts, were all inhibited by the M20 IL-1 Inhibitor. In vivo, the IL-1 Inhibitor reduced parameters of acute inflammation such as fever, leukocytosis and local inflammation. This study describes additional effects of the M20 IL-1 Inhibitor on inflammatory serum reactants. Levels of corticosterone and fibrinogen were increased by injection of IL-1, and decreased by the IL-1 Inhibitor. IL-1 reduced zinc and iron plasma levels and elevated copper plasma levels. The M20 IL-1 Inhibitor reversed these changes in a dose dependent manner. Similar effects produced by IL-6 and TNF were unaffected by the M20 IL-1 Inhibitor. Our results indicate that the M20 IL-1 Inhibitor acts specifically on IL-1 induced responses in vivo. Therefore we conclude that this IL-1 Inhibitor has a great potential as an anti-inflammatory agent.

In vivo anti inflammatory effects of the M20 IL-1 inhibitor: I. Effects on acute inflammatory parameters

Previous studies have described an IL-1 Inhibitor produced by a myelomonocytic line developed in our laboratory (Eur J Immunol 1986; 16: 1449). This IL-1 Inhibitor was secreted by the M20 line constitutively in addition to IL-1, from which it could be separated. We have recently shown that the M20 IL-1 Inhibitor is distinct from the IL-1ra. In vitro this factor inhibited IL-1 induced proliferative responses as well as PGE2 secretion by IL-1 induced fibroblasts. We also showed for the first time (Lymphokine Research 1988; 7(3): 268) that an IL-1 inhibitor can reduce IL-1 induced inflammatory effects. This study describes the specific effect of the M20 IL-1 Inhibitor on IL-1 induced parameters of inflammation: fever, leukocytosis and local foot pad swelling or lymph node enlargement. Purified preparations of the IL-1 Inhibitor, when injected together with IL-1, or before the IL-1, reduced fever, leukocytosis, foot pad swelling and lymph node enlargement caused by IL-1. Similar responses were obtained by injection of IL-6 or TNF, but were unaffected by the IL-1 Inhibitor, when injected together. These results indicate that the M20 IL-1 Inhibitor acts specifically on IL-1 induced responses in vivo. The potential importance of this factor as an anti-inflammatory and immune regulatory factor, is supported by the findings of this study.

Binding of cytokines to pharmaceutically prepared human immunoglobulin

Pharmaceutically prepared IgG, pooled from sera of over 2,000 normal individuals, contained both monomeric and dimeric IgG. Each type of IgG bound 125I-labeled interleukin (IL)-1 alpha, IL-1 beta, IL-6, and tumor necrosis factor (TNF)-alpha. Increased binding to IgG was observed if 125I-IL-1 beta was denatured by heating to 39 degrees C. However, the binding of both nondenatured and denatured 125I-IL-1 beta was not inhibited by unlabeled IL-1 beta. In contrast, binding of 125I-IL-1 alpha, 125I-IL-6, and 125I-TNF alpha was inhibited by the corresponding unlabeled cytokine. Papain-digestion of IgG abolished binding of 125I-TNF alpha but failed to influence the displaceable binding of 125I-IL-1 alpha and 125I-IL-6. 125I-TNF alpha was a mixture of trimeric and monomeric forms, the latter being the predominant form at lower concentrations. The apparent saturability of 125I-TNF alpha was explained by a higher nonspecific binding of monomeric than of trimeric 125I-TNF alpha to IgG. The amounts of cytokine antibodies in IgG preparations would contribute approximately 2 micrograms anti-IL-1 alpha IgG and 1 microgram anti-IL-6 IgG per kg body wt during high dose immune globulin therapy. In conclusion, pharmaceutical preparations of human IgG contain specific and neutralizing, high affinity antibodies against IL-1 alpha and IL-6, but not against TNF alpha or IL-1 beta. There are significant methodological pitfalls that hamper detection of IgG autoantibodies against cytokines.

Fever: causes and consequences

The present review distinguishes pathogenic, neurogenic, and psychogenic fever, but focuses largely on pathogenic fever, the hallmark of infectious disease. The data presented show that a complex cascade of events underlies pathogenic fever, which in broad outline - and with frank disregard of contradictory data - can be described as follows. An invading microorganism releases endotoxin that stimulates macrophages to synthesize a variety of pyrogenic compounds called cytokines. Carried in blood, these cytokines reach the perivascular spaces of the organum vasculosum laminae terminalis (OVLT) and other regions near the brain where they promote the synthesis and release of prostaglandin (PGE2). This prostaglandin then penetrates the blood-brain barrier to evoke the autonomic and behavioral responses characteristic of fever. But then once expressed, fever does not continue unchecked; endogenous antipyretics likely act on the septum to limit the rise in body temperature. The present review also examines fever-resistance in neonates, the blunting of fever in the aged, and the behaviorally induced rise in body temperature following infection in ectotherms. And finally it takes up the question of whether fever enhances immune responsiveness, and through such enhancement contributes to host survival.

Early induction of IL-1 receptor antagonist (IL-1Ra) in infants and children undergoing surgery

The cytokine response to injury or trauma is of interest in terms of both its mediation of the acute phase response and its possible relation to the immunological depression observed after major surgery. In this study, the production of cytokines IL-1 beta, tumour necrosis factor-alpha (TNF-alpha), IL-6 and the naturally occurring inhibitor of IL-1, IL-1Ra, have been investigated in infants and children undergoing Swenson's pull-through operation for Hirschsprung's disease. Samples of peripheral blood were taken before, during and after surgery for the measurement of cytokines. IL-1Ra levels increased significantly (P < 0.01) at 2 h after commencement of surgery, with maximal levels for individual patients being attained between 3 h and 5 h (range 7.6-67.9 ng/ml). The mean level of IL-1Ra was maximal (26.2 ng/ml) at 5 h and returned to baseline levels between 24 h and 72 h. There were no changes observed in the circulating levels of IL-1 beta in nine out of 11 patients following commencement of surgery. TNF-alpha levels did not increase in any of the patients studied. IL-6 levels increased significantly (P < 0.02) 3 h after commencement of surgery, reaching maximum concentrations at 24 h (range 20-670 pg/ml), with levels falling between 48 h and 72 h. This study demonstrates, in vivo, the independent induction of IL-1Ra without a concomitant increase of IL-1 beta levels after major surgery. It also shows that IL-1Ra is the earliest cytokine produced in response to surgical stress.

In vivo cytokine expression in normal and perturbed murine skin--analysis by competitive quantitative polymerase chain reaction

Although cells from both epidermis and dermis have been shown to produce a variety of soluble mediators in vitro, it is not clear whether this reflects the in vivo situation. To study in vivo cytokine expression, whole skin as well as dispase-separated epidermis and dermis from normal adult mice were prepared and snap-frozen immediately. RNA was then extracted and analyzed both by conventional and by competitive quantitative polymerase chain reaction. Molecular analysis showed that murine skin in vivo constitutively expresses several cytokine genes at moderate (e.g., interleukin-1 alpha) or low (e.g., interleukin-6 and granulocyte-macrophage colony-stimulating factor) abundance. A striking, rapid upregulation was observed for some of these cytokines in the process of tissue separation. Of interest, the epidermal and dermal compartments exhibited different induction patterns: interleukin-1 alpha, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor-alpha expression were detected preferentially in the epidermis, whereas upregulation of interleukin-6 was found to be most prominent in the dermis. This pattern of cytokine expression was also reflected in supernatants generated from the respective single-cell suspensions. Thus, this study determines the baseline in vivo cytokine expression in the skin and the occurrence of immediate, compartment-specific alterations on perturbation. These data should contribute to our understanding of both skin homeostasis and the host-defense mechanisms initiated following injury to this organ.

Cytokine mediators of septic infections in the normal and granulocytopenic host

Cytokines presently known to be involved in systemic bacterial infection are tumour-necrosis factor (TNF), interleukin (IL)-1, IL-6, IL-8 and interferon-gamma (IFN-gamma) and the counterregulatory molecules soluble TNF receptor (sTNFR) and IL-1 receptor antagonist (IL-1 Ra). In animal models TNF, IL-1 and IFN-gamma mediate organ damage, low blood pressure and fatality, whereas IL-6 is involved in infection-related manifestations, like the production of acute-phase protein and fever, and IL-8 is chemotactic to granulocytes. TNF and IL-1 increase expression of adhesion molecules on endothelial cells and influence a number of components of the haemostatic system in favour of coagulation. The presence of cytokines in the circulation is characterized by sequential releases of TNF, IL-1 and IL-6/IL-8; however, many variations of this pattern exist during human infection. In experiments as well as in human infection TNF, IL-1, IL-6, IL-8 and IFN-gamma have been detected, and levels of TNF, IL-6 and IL-8 have been found to be associated with the severity of the disease. Collectively, TNF, IL-1 and IFN-gamma emerge as mediators of systemic infection and septic shock whereas IL-6 and IL-8 are related to other manifestations of infection. Counteracting molecules like sTNFR are released after somewhat of a delay following TNF and IL-1Ra is released concomitantly with IL-1. Probably these factors modulate the cytokine effect although their true potency in natural infection has yet to be clarified. In granulocytopenic infections TNF, IL-1, IL-6 and IL-8 can be detected in serum, and levels of TNF and IL-6 are even higher than in the normal situation in experimental animals. Antibodies to TNF inhibit bacteria-induced fatality in granulocytopenic mice. Altogether, few data related to the granulocytopenic situation are available. However, it is reasonable to believe that the altered development of granulocytopenic infections is due to changes in the cellular constitution and not to changes in cytokine production.

Post-translational regulation of interleukin 1 beta secretion

In view of the key role played by interleukin 1 (IL-1) beta in inflammation, its production is likely to be precisely regulated. Previous studies have shown that IL-1 beta biosynthesis is controlled at the transcriptional and translational levels. We have investigated whether post-translational events also play a role in regulating the production of bioactive IL-1 beta. IL-1 beta, which lacks a signal sequence, is released by activated monocytes through a novel pathway of secretion, alternative to the classical endoplasmic reticulum-Golgi route. Secretion of mature 17 kDA IL-1 beta is increased when pulse-labelled activated monocytes are chased in the presence of heat-aggregated immunoglobulins or of various drugs. Febrile temperatures inhibit secretion of mature IL-1 beta, but only reduce its synthesis: treatment with cycloheximide restores secretion. Processing of the 33 kDa precursor to the 17 kDa mature molecule is inhibited when the external pH is 8 or higher: under these conditions, release of unprocessed, biologically inactive 33 kDa IL-1 beta is observed. Thus, secretion of IL-1 beta is regulated by post-translational mechanisms which operate at the level of both proteolytic processing and extracellular export.

Interleukin-1 receptor antagonist

IL-1ra is the first described naturally occurring receptor antagonist of any cytokine or hormone-like molecule. IL-1ra is a member of the IL-1 family by three criteria: amino acid sequence homology of 26 to 30% to IL-1 beta and 19% to IL-1 alpha; similarities in gene structure; and common gene localization to human chromosome 2q14. Two structural variants of IL-1ra exist: sIL-1ra, a secretory molecule produced by monocytes, macrophages, neutrophils, fibroblasts, and other cells; and icIL-1ra, an intracellular molecule produced by keratinocytes and other epithelial cells, macrophages, and fibroblasts. IL-1ra production by monocytes, macrophages, and neutrophils may be regulated in a differential fashion with IL-1 beta. Human IL-1ra binds to both human IL-1RIs and IL-1RIIs on cell surfaces, although with 100-fold greater avidity to IL-1RIs. IL-1ra may bind preferentially to soluble IL-1RIs and not at all to soluble IL-1RIIs. IL-1ra competitively inhibits binding of both IL-1 alpha and IL-1 beta to cell surface receptors without inducing any discernible intracellular responses. All three forms of IL-1 may bind to IL-1 receptors in a similar fashion but IL-1ra may lack the secondary interactions necessary to trigger cell responses. A 100-fold or greater excess of IL-1ra over IL-1 may be necessary to inhibit biological responses to IL-1 both in vitro and in vivo. The roles of sIL-1ra and icIL-1ra in normal physiology or in host defense mechanisms remain unclear. The administration of IL-1ra blocks the effects of IL-1 in some animal models of septic shock, inflammatory arthritis, graft-versus-host disease, and inflammatory bowel disease. The preliminary results of clinical trials in humans indicate possible efficacy of IL-1ra in sepsis syndrome, rheumatoid arthritis, and GVHD.

Cytokine production and serum levels in systemic sclerosis

Serum levels of various cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin 1-beta (IL1-beta), and interleukin 2 (IL2), and of soluble IL2 receptors (sIL2R) were determined in 30 patients with definite systemic sclerosis (SSc). Spontaneous and lipopolysaccharide-or mitogen-induced production of the cytokines, TNF-alpha, IL1-beta, and IFN-gamma, by peripheral blood mononuclear cells (PBMNC) of these SSc patients was measured by immunoassays. The patients were divided into three groups: 12 with limited cutaneous disease (lcSSc), 7 with diffuse cutaneous disease (dcSSc) < 3 years duration, and 11 with dcSSc > 3 years duration. None were treated with cytotoxic drugs or biologic response modifiers. Sera of patients with SSc had elevated sIL2R levels, and only low levels of IL2 (1-2 U/ml) were detected in 10/29 sera tested. Spontaneous production of TNF-alpha and IL1-beta by PBMNC of patients with SSc (829 pg/ml +/- 215 SEM and 728 pg/ml +/- 186, respectively) was significantly higher than that by normal PBMNC obtained from 30 volunteers (25 +/- 10 and 34 +/- 6 pg/ml, respectively) and tested at the same time as patients' PBMNC. The largest increases in spontaneous release of TNF-alpha or IL1-beta were seen in patients with early dcSSc. No significant difference in spontaneous IFN-gamma production by patient or control PBMNC was detected. On the other hand, the mean level of mitogen-induced IFN-gamma production by PBMNC was significantly depressed in patients with SSc (103 U/ml +/- 18 vs 255 +/- 33 U/ml in controls). In vitro-induced production of TNF-alpha or IL1-beta by patients' PBMNC was comparable to that of normal PBMNC. These data indicate that in vivo-activated PBMNC of patients with SSc spontaneously secrete excessive amounts of fibrogenic cytokines, which are involved in modulation of connective tissue synthesis.

The M20 IL-1 inhibitor prevents onset of adjuvant arthritis

Cytokines, specifically IL-1 and TNF, have been implicated as important mediators of joint destruction in rheumatoid arthritis (RA). Elevated levels of IL-1 in the joint fluid of patients with RA have been reported, as well as the presence of IL-1 inhibitory activity. We have reported the characterization of an inhibitor derived from a myelomonocytic cell line cloned in our laboratory which is specific for IL-1. This IL-1 inhibitor is protein in nature which specifically inhibits activity in vitro and in vivo. Previous studies showed that the inhibitor reduced acute inflammatory reactions associated with IL-1 (fever, leukocytosis, local foot pad swelling, lymph node enlargement and acute phase reactants). Thus it was of interest to study whether the M20 IL-1 inhibitor could modify adjuvant-induced chronic inflammation in rats, which is often used as a model for human RA. Administration of complete Freund's adjuvant (CFA) into Lewis rats, resulted in a severe adjuvant arthritis (AA) which reached peak severity after 14 days. Daily administration of IL-1 inhibitor, beginning after injection of CFA, abolished the appearance of AA. The parameters investigated were: joint swelling (the increase in diameter of joints), peri-articular erythema, limping of the rats and histological examination. The effect of the M20 IL-1 inhibitor was shown to be dose dependent and the IL-1 inhibitor alone had no adverse effects. These results indicate that the M20 IL-1 inhibitor may have a role in the treatment of AA and may be used to reduce pathological processes in joint inflammation.

The M20 IL-1 inhibitor. II. Biological characterization

Interleukin-1 (IL-1) is an important mediator in inflammation and immunological processes. The findings of native IL-1 inhibitors suggest a negative feedback mechanism to down-regulate IL-1 mediated acute inflammation. IL-1 inhibitors were also found elevated in disease states associated with high IL-1 levels. We have previously described one such IL-1 inhibitor derived from the human M20 myelomonocytic cell line. In this paper we present several biological and biochemical characteristics of the M20 IL-1 inhibitor. Various in vitro activities of the inhibitor are described and its IL-1 specificity in these assays is demonstrated. Purification of the inhibitor was performed by DEAE-high performance liquid chromatography, isoelectric focusing, gel filtration and dye ligand chromatography column. This protein factor has a MW of 52 +/- 4 kDa and a pI of 4.15 +/- 0.1. The inhibitor has no cross-reactivity against a panel of known cytokines (IL-1 alpha, IL-1 beta, IL-2, sIL-2R, IL-6, tumor necrosis factor (TNF), interferon-gamma (IFN-gamma)) and is distinct from the IL-1 receptor antagonist (IL-1ra). The purified IL-1 inhibitor was destroyed by trypsin, 2-mercaptoethanol, sodium dodecyl sulfate and extremes in pH and in temperature. Only IL-1 induced (but not the IL-2, IL-6 or TNF induced) thymocyte proliferation and PGE2 production by fibroblasts were inhibited by the inhibitor, thus showing specificity to IL-1 in these assays.

The M20 IL-1 inhibitor. I. Purification by preparative isoelectric focusing in free solution

An interleukin-1 (IL-1) inhibitor produced by the M20 myelomonocytic cell line has been shown to be active in various in vitro and in vivo IL-1 induced parameters. This inhibitor has been purified from the conditioned medium by gel filtration through a Sephacryl S-300 column or dye ligand chromatography on Affi-Gel blue column, followed by isoelectric focusing in free solution in the pH range 3-5 using the Rotofor cell. When gel filtration by FPLC with the Superose 12 column was used as the final step, the combined sequence of purification procedures resulted in a 1600-fold purification of the IL-1 inhibitor. The purified IL-1 inhibitor has a molecular weight of approximately 52 +/- 4 kDa and a pI of 4.15 +/- 0.1. By SDS-PAGE analysis the inhibitor preparation thus obtained showed the presence of two protein bands, while a few closely spaced protein bands were seen by analytical isoelectric focusing in polyacrylamide gels (pH 3-6). Some of these bands in PAGIF might correspond to different degrees of glycosylation of the inhibitory protein. Although the M20 IL-1 inhibitor has not yet been purified to homogeneity, it should be stressed that the procedures used, allowed us to remove the great majority of the proteins present in the medium in which the M20 cells were cultured, and to recover in satisfactory yield the inhibitor which we consider likely to be present in the conditioned medium in subnanomolar concentrations.

A soluble receptor for interleukin-1 beta encoded by vaccinia virus: a novel mechanism of virus modulation of the host response to infection

Vaccinia virus gene B15R is shown to encode an abundant, secretory glycoprotein that functions as a soluble interleukin-1 (IL-1) receptor. This IL-1 receptor has novel specificity since, in contrast with cellular counterparts, it binds only IL-1 beta and not IL-1 alpha or the natural competitor IL-1 receptor antagonist. The vaccinia IL-1 beta receptor is secreted when expressed in a baculovirus system and competitively inhibited binding of IL-1 beta to the natural receptor on T cells. Deletion of B15R from vaccinia virus accelerated the appearance of symptoms of illness and mortality in intranasally infected mice, suggesting that the blockade of IL-1 beta by vaccinia virus can diminish the systemic acute phase response to infection and modulate the severity of the disease. The IL-1 beta binding activity is present in other orthopoxviruses.