A metalloproteinase inhibitor blocks the shedding of soluble cytokine receptors and processing of transmembrane cytokine precursors in human monocytic cells

A number of membrane-anchored cytokines and cytokine receptors are susceptible to yield soluble counterparts. Recently, peptide-hydroxamate metalloproteinase inhibitors have been reported to block the proteolytic processing of tumour necrosis factor (TNF)-alpha 55- and 75-kDa TNF receptors (TNF-R55 and TNF-R75), and interleukin (IL)-6R. In this report the authors studied the effect of an hydroxamate metalloproteinase inhibitor on the secretion of cytokines and the generation of cytokine soluble receptors by human myelomonoycytic cell lines and purified monocytes. Whereas secretion of cytokines lacking a transmembrane domain precursor (IL-1 alpha, IL-1 beta, IL-6 or IL-10) is either unaffected or augmented, shedding/secretion of transmembrane domain-containing cytokines and cytokine receptors [TNF-alpha, macrophage colony-stimulating factor (M-CSF), transforming growth factor (TGF)-alpha, stem cell factor (SCF), TNF-R55, TNF-R75, and IL-6R] was dramatically decreased in the presence of the metalloproteinase inhibitor. The diversity of sequences in the cleavage site of these proteins and differences found in the inhibitory concentration values suggest the existence of a metalloproteinase family displaying different substrate specificity. These results emphasize the important role of metalloproteinases as regulators of membrane expression and secretion of cytokines and cytokine receptors.     

TNF-induced superoxide anion production in adherent human neutrophils involves both the p55 and p75 TNF receptor

TNF, a potent activator of neutrophil granulocytes, acts via two cell-surface receptors: the p55-TNF receptor (TNF-R55) and the p75-TNF receptor (TNF-R75), which can be cleaved from the cell surface and thus form soluble TNF-binding proteins (TNF-BP). The role of the two receptors in activation of the neutrophil respiratory burst was investigated. Two mAbs reacting with TNF-R55 (H398 and TBP2) induced O2 release in a similar manner but to a lesser extent than TNF. TBP2, however, required preincubation at 4 degrees C to exert its effect. Preincubation of neutrophils (both at 4 and 37 degrees C) with mAb to TNF-R75 decreased TNF-induced superoxide anion production by 67 and 64%, respectively, indicating the essential role also for TNF-R75 in neutrophil activation. This inhibitory effect could not be explained by cross-down-regulation of TNF-R55 because the TNF-R75 mAb had no effect on TNF binding to TNF-R55 as determined by binding of 125I-labeled TNF or release of TNF-R55-BP as measured by ELISA. Furthermore, the TNF-R75 mAb did not decrease superoxide anion generation induced by the TNF-R55 mAb H398, thus ruling out that the inhibitory effect of the TNF-R75 mAb is due to inhibition of the signaling pathway downstream of TNF-R55. In contrast to the TNF-R75 mAb, TNF-R55 mAbs induced down-regulation of TNF-R75 and shedding of both TNF-R55-BP and TNF-R75-BP. We conclude that both TNF-R55 and TNF-R75 are involved in TNF-induced activation of the neutrophil respiratory burst.     

TNF-alpha, unlike other pro- and anti-inflammatory cytokines, induces rapid release of the IL-1 type II decoy receptor in human myelomonocytic cells

The present study was designed to investigate the effect of a series of cytokines on the release of the type II IL-1 decoy receptor, which represents a unique pathway of negative regulation of the IL-1 system. After 20 min, IL-1, IL-2, IL-4, IL-6, IL-10, IL-12, IL-13, IFN-gamma, granulocyte-CSF, macrophage-CSF, and TGF-beta had little or no effect on IL-1 binding by human polymorphonuclear cells. In contrast granulocyte-macrophage-CSF and, to a greater extent, TNF markedly reduced IL-1 binding. The action of TNF was rapid, reaching 50% of its maximum (80%) at 2 min, and plateauing at 20 min with decrease in receptor number and no significant change in affinity. Loss of surface receptor was associated to rapid release of a 45-kDa IL-1-binding molecule identified as the decoy RII. TNF-induced release of the decoy RII was independent of protein synthesis and reactive oxygen intermediates. Monocytes showed a similar response to TNF, except for the size of the released molecule (approximately 60 kDa). TNF induced rapid release of its own receptors. In contrast IL-1beta affected neither its own receptors nor the TNF-R. TNF and, more efficiently, PMA caused release of the decoy RII in fibroblasts transfected with the full-length decoy RII or with a cytoplasmatic deletion mutant. TNF-induced decoy RII release represents an unidirectional pathway of communication in the interplay between the IL-1 and TNF system.     

Soluble cytokine receptors and receptor antagonists are sequentially released after trauma

Cytokine receptors and receptor antagonists (RAs) have been identified in trauma patients. We hypothesized that after traumatic injury, a sequential release of soluble cytokine receptors and RAs may exist that mirrors the release of the primary cytokines themselves. Twenty-two patients were included in the study: 14 males and 8 females. The mean age was 30.1 +/- 12.5 (range, 19 to 71), and the mean Injury Severity Score was 28.7 +/- 12.6 (range, 4 to 57). There were 15 survivors and 7 nonsurvivors. Samples were collected on arrival to the emergency department and at serial intervals for up to 7 days. Monoclonal antibody enzyme-linked immunosorbent assay kits to tumor necrosis factor (TNF), soluble TNF-receptor (sTNF-R) 55 kd and 75 kd, interleukin (IL)-1 and IL-1 RA, and IL-2 and IL-2r were used. Sera from 22 healthy individuals were used as normal controls. No TNF, IL-1, or IL-2 could be detected in any patient sera after injury. Control levels for the soluble cytokine receptors and RAs were as follows: sTNF-R 55 kd, 607 +/- 89 pg/mL; sTNF-R 75 kd, 2,141 +/- 169 pg/mL; IL-1 RA, 291 +/- 35 pg/mL; and IL-2r, 426 +/- 53 U/mL. In trauma patients, both 55 kd and 75 kd sTNF-R were significantly elevated on arrival to the emergency department, with values of 2,441 +/- 506 pg/mL (p < 0.001) and 4,736 +/- 537 pg/mL (p < 0.001), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

TNF receptor p55 plays a major role in centrally mediated increases of serum IL-6 and corticosterone after intracerebroventricular injection of TNF

The aim of this work was to study the relative role of the two TNF receptors (p55 and p75) in the central actions of TNF, studying the elevation of serum corticosterone (CS) and IL-6 levels after injection of recombinant murine (rm)TNF (intracerebroventricularly (i.c.v.)) in normal or p55-deficient (p55 -/-) mice. rmTNF induced high serum IL-6 levels and doubled serum CS in normal mice, whereas no elevation of serum IL-6 or CS was induced in p55 -/- mice. However, a normal CS response was observed in p55 -/- mice after LPS (2.5 microg, i.c.v.). p55 -/- mice also responded, although to a lesser extent than p55 +/+, in terms of LPS-induced IL-6 production. We also injected two agonist Abs specific for the two receptors, alpha p55 and alpha p75. While alpha p55 injected i.c.v. induced a marked elevation in CS and IL-6, alpha p75 induced CS (although less than alpha p55) but no IL-6. rmTNF, which binds both receptors, was more potent in inducing IL-6 and CS than injection of rhTNF, which in mice binds only p55. Finally, we investigated the role of p55 and p75 in IL-6 induction by TNF in a murine brain endothelioma. The results resembled closely those obtained in vivo: rmTNF was more potent than rhTNF and only alpha p55, and not alpha p75, induced IL-6 production. These data indicate that p55 plays a major role in TNF activation of the hypothalamus-pituitary-adrenal axis and in the centrally mediated induction of peripheral IL-6 by TNF, but p75, despite having little IL-6 inductive properties by itself, seems to potentiate p55 induction of IL-6.     

Effects of interleukins on secretion of luteinizing hormone from ovine pituitary cells

OBJECTIVE: To determine whether cytokines of homologous species might mediate the stimulatory effects of endotoxin on release of luteinizing hormone (LH) from pituitary cells. SAMPLE POPULATION: Cells from pituitary glands collected from 8- to 14-month-old wethers. PROCEDURE: Cells from the anterior pituitary gland were cultured in the presence of recombinant ovine or bovine cytokines (interleukin [IL]-1alpha, IL-1beta, and IL-2), tumor necrosis factor-alpha (TNF), and interferon-gamma (IFN-gamma). Luteinizing hormone that was released into the medium was measured. Cells were also cultured with modulators of signal transduction pathways to evaluate the second messenger system used by IL-1 alpha and IL-1beta. RESULTS: Similar to effects of endotoxin, IL-1alpha and IL-1beta stimulated release of LH. Interleukin 2, TNF, and IFN-gamma did not have a detectable effect on release of LH. Stimulation of LH release by IL-1alpha and IL-1beta required activation of voltage-dependent Ca2+ channels and appeared to involve protein kinase C. CONCLUSIONS: IL-1alpha and IL-1beta may mediate the direct stimulatory effect of endotoxin on release of LH in vitro. Interleukin 2, TNF, and IFN-gamma do not have a direct effect on release of LH; therefore, they do not mediate this effect of endotoxin. CLINICAL RELEVANCE: Stressors, including infection, are often associated with reduced fertility. Infection resulting in endotoxin release, production of interleukins, or both, can lead to direct stimulation of LH release from the pituitary gland. Inopportune release of LH via cytokines may interfere with normal pulsatile release of LH, thereby suppressing gonadal function.     

Interleukin-6, gamma interferon, and tumor necrosis factor receptors in typhoid fever related to outcome of antimicrobial therapy

To study mechanisms of antibiotic effects in typhoid fever, levels of interleukin-6 (IL-6), gamma interferon (IFN-gamma), and cytokine receptors (tumor necrosis factor receptor [TNF-R] p55 and TNF-R p75) were measured in the plasma of 29 adult Nepalese with culture-positive typhoid fever before therapy and on days 4 and 15 after start of therapy with either ceftriaxone at 2 g/day for 3 days or chloramphenicol at 50 mg/kg of body weight per day for 14 days. Bacteriologic cure was defined as blood cultures testing negative on days 4 and 15 after start of therapy; clinical cure was defined as symptomatic improvement within 5 days after start of therapy and absence of relapse. Clinical and bacteriologic cures occurred in 24 patients. There were two clinical failures, two patients who failed to complete therapy because of leukopenia, and one relapse. Mean levels before therapy were elevated compared with those in healthy controls (IL-6, 11.4 pg/ml; IFN-gamma, 1.3 ng/ml; TNF-R p55, 3.8 ng/ml; and TNF-R p75, 6.1 ng/ml) and fell progressively during and after therapy. For six patients (three in each treatment group) who showed prolonged fever (> 5 days) or relapse, mean levels of IL-6 and TNF-R p55 before therapy (29.5 pg/ml and 6.1 ng/ml, respectively) and on day 4 (17.7 pg/ml and 4.0 ng/ml) were significantly greater than corresponding means for 23 patients who showed early defervescence (on admission, 6.7 pg/ml and 3.3 ng/ml, and on day 4, 1.8 pg/ml and 2.7 ng/ml, P < .05). These results indicate that the concentrations of plasma cytokines and their receptors are elevated in typhoid fever and that these concentrations can be useful in predicting outcome.     

Measuring the quality of outpatient treatment for schizophrenia

OBJECTIVE: Usually it is not possible to study the initial systemic response in patients with acute pancreatitis in the first hours after onset of the disease. We used postendoscopic retrograde pancreatography (ERP) pancreatitis as a model to study cytokine and anticytokine release in the early phase of human acute pancreatitis. METHODS: Post-ERP pancreatitis was defined as a threefold increase in serum amylase and at least two of the following clinical symptoms: abdominal pain, nausea, vomiting or peritonism 24 h after ERP. Serum levels of pro-inflammatory cytokines interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interleukin-8 (IL-8), tumour necrosis factor alpha (TNF), as well as endogenous antagonistic mediators of the systemic inflammatory response such as soluble tumour necrosis factor alpha receptors p55 (TNFR p55) and p75 (TNFR p75), and IL-1-receptor antagonist (IL-1-RA) and interleukin-2-receptor (IL-2R) as indicators of lymphocyte activation were measured before and 0, 1, 4, 12, 24 and 48 h after ERP. In nine patients with acute post-ERP pancreatitis, these parameters were monitored daily until C-reactive protein (CRP) was within normal ranges and were compared to patients without pancreatitis after ERP. RESULTS: IL-1beta was not detectable in five patients with and four patients without post-ERP pancreatitis. The values of the remaining patients in both groups were lower than 3.9 pg/ml. IL-8 and IL-1-RA serum concentrations peaked 12 h after ERP (132.9 and 3245.0 pg/ml respectively) compared to patients without post-ERP pancreatitis (25.8 and 389.9 pg/ml respectively). The IL-6 concentration increased to 81.6 pg/ml (8.0 pg/ml in control patients) 24 h after ERP, while the peak values for CRP were measured 72 h after ERP (164.0 versus 7.7 mg/l). IL-2R content was maximally elevated 144 h after ERP (688.8 versus 255.9 U/ml), while concentrations of TNF and its receptors showed no significant change over time. CONCLUSION: The initial response of the cytokine network to damage of the human pancreas leading to acute pancreatitis includes the release of IL-8 and the IL-1 antagonist IL-1-RA, while IL-1beta is not found in the systemic circulation. The TNF system does not seem to be involved as indicated by the lack of detectable changes in TNF and the soluble TNFR p55 and p75 serum concentrations. Lymphocyte activation as indicated by elevated IL-2R levels occurred days after the initial trauma. Even mild post-ERP pancreatitis leads to significant systemic release of cytokines and their biological counterparts.     

Gene expression and secretion of cytokines and cytokine receptors from highly purified CD56+ natural killer cells stimulated with interleukin-2, interleukin-7 and interleukin-12

Interleukin (IL)-2 IL-7 and IL-12 stimulate the generation of lymphokine-activated killer activity and proliferation in natural killer (NK) cells by different mechanisms. In this study, we have compared the ability of IL-2, IL-7 and IL-12 to induce expression of cytokines and cytokine receptors both at the gene and protein level. IL-2 and IL-12 stimulated the CD56+ NK cells to release significant amounts of soluble p55 and p75 tumor necrosis factor receptor (TNFR), whereas less amounts of soluble TNFR were detected in IL-7-stimulated cultures. The p55 and p75 TNFR mRNA were expressed in resting NK cells, and no further induction was observed after cytokine-stimulation. Compared to the effects of IL-2, IL-7 induced lower, but substantial levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA, and IL-7 was a more potent GM-CSF-inducing stimulus than IL-12. IL-12 induced higher levels of interferon-gamma (IFN-gamma) mRNA than did IL-2, and IL-7 only weakly influenced the IFN-gamma expression. In accordance with the mRNA studies, IL-7 induced the secretion of high amounts of GM-CSF and no or low levels of IFN-gamma, whereas high amounts of IFN-gamma and low levels of GM-CSF were detected in supernatants from IL-12-stimulated NK cells. In conclusion, IL-2, IL-7 and IL-12 differentially regulate expression of cytokines and cytokine receptors both at the gene and protein level.     

A critical role of the p75 tumor necrosis factor receptor (p75TNF-R) in organ inflammation independent of TNF, lymphotoxin alpha, or the p55TNF-R

Despite overwhelming evidence that enhanced production of the p75 tumor necrosis factor receptor (p75TNF-R) accompanies development of specific human inflammatory pathologies such as multi-organ failure during sepsis, inflammatory liver disease, pancreatitis, respiratory distress syndrome, or AIDS, the function of this receptor remains poorly defined in vivo. We show here that at levels relevant to human disease, production of the human p75TNF-R in transgenic mice results in a severe inflammatory syndrome involving mainly the pancreas, liver, kidney, and lung, and characterized by constitutively increased NF-kappaB activity in the peripheral blood mononuclear cell compartment. This process is shown to evolve independently of the presence of TNF, lymphotoxin alpha, or the p55TNF-R, although coexpression of a human TNF transgene accelerated pathology. These results establish an independent role for enhanced p75TNF-R production in the pathogenesis of inflammatory disease and implicate the direct involvement of this receptor in a wide range of human inflammatory pathologies.     

Dimerization of chimeric erythropoietin/75 kDa tumour necrosis factor (TNF) receptors transduces TNF signals: necessity for the 75 kDa-TNF receptor transmembrane domain

We developed a transfection-based assay for evaluating human (h) Tumour Necrosis Factor receptor (TNF-R) activities in a rat/mouse T-cell hybridoma, viz. PC60. Here we report on the role of TNF-R75 cross-linking in induction of GM-CSF secretion and apoptosis. The effect of TNF-R75 dimerization, in contrast to trimerization, was analysed by replacing the extracellular domain of this receptor with the equivalent domain of the murine erythropoietin receptor (EPO-R), which dimerizes upon ligand interaction. To determine the role of the transmembrane region in signal transduction, chimeric EPO-R/TNF-R75 were constructed in which the respective transmembrane domains were interchanged. The hybrid receptors were introduced into PC60hTNFR55 cells, which already expressed functional, transfected hTNF-R55. By this approach we demonstrated that dimerized chimeric EPO-R/TNF-R75 receptors act synergistically with hTNF-R55-induced cytokine production and apoptosis as does trimerized wild-type hTNF-R75. Dimeric triggering of these hybrid receptors with EPO alone was less efficient than trimerization of hTNF-R75. Furthermore, EPO-R/TNFR75 only responded to EPO when the matching transmembrane region of TNF-R75 was present. Our results also prove that the hTNF-R75 extracellular part per se is not required for signalling. Finally, our data indicate that the expression of chimeric EPO-R/TNF-R75 in PC60hTNF-R55 cells, regardless of the presence of the TNF-R75 transmembrane region, facilitates TNF-R55-dependent signal transduction leading to apoptosis. This means that introduction of the intracellular domain of hTNF-R75, even without triggering, is sufficient to promote hTNF-R55-dependent activities in PC60 cells.     

Inhibition of interferon gamma induced interleukin 12 production: a potential mechanism for the anti-inflammatory activities of tumor necrosis factor

Inflammation is associated with production of cytokines and chemokines that recruit and activate inflammatory cells. Interleukin (IL) 12 produced by macrophages in response to various stimuli is a potent inducer of interferon (IFN) gamma production. IFN-gamma, in turn, markedly enhances IL-12 production. Although the immune response is typically self-limiting, the mechanisms involved are unclear. We demonstrate that IFN-gamma inhibits production of chemokines (macrophage inflammatory proteins MIP-1alpha and MIP-1beta). Furthermore, pre-exposure to tumor necrosis factor (TNF) inhibited IFN-gamma priming for production of high levels of IL-12 by macrophages in vitro. Inhibition of IL-12 by TNF can be mediated by both IL-10-dependent and IL-10-independent mechanisms. To determine whether TNF inhibition of IFN-gamma-induced IL-12 production contributed to the resolution of an inflammatory response in vivo, the response of TNF+/+ and TNF-/- mice injected with Corynebacterium parvum were compared. TNF-/- mice developed a delayed, but vigorous, inflammatory response leading to death, whereas TNF+/+ mice exhibited a prompt response that resolved. Serum IL-12 levels were elevated 3-fold in C. parvum-treated TNF-/- mice compared with TNF+/+ mice. Treatment with a neutralizing anti-IL-12 antibody led to resolution of the response to C. parvum in TNF-/- mice. We conclude that the role of TNF in limiting the extent and duration of inflammatory responses in vivo involves its capacity to regulate macrophage IL-12 production. IFN-gamma inhibition of chemokine production and inhibition of IFN-gamma-induced IL-12 production by TNF provide potential mechanisms by which these cytokines can exert anti-inflammatory/repair function(s).     

Peripheral monocyte culture supernatants of menopausal women can induce bone resorption: involvement of cytokines

Increased bone resorption is a mechanism contributing to bone loss in the postmenopausal period. Cytokines are involved in osteoclastic differentiation and, therefore, may play a role in the regulation of bone resorption. Several previous works showed the implication of interleukin-1 (IL-1), IL-6, and tumor necrosis factor-alpha (TNF alpha) in the modulation of bone remodeling. This study determines the concomitant production of the three cytokines and tests the bone-resorbing activity of peripheral monocyte supernatants. Four groups of women were studied: premenopausal women (n = 13; mean age, 47 +/- 0.9 yr), untreated postmenopausal women (n = 21; mean age, 52 +/- 0.6 yr), postmenopausal women treated with estrogens (n = 14; mean age, 54.2 +/- 1.1 yr), or postmenopausal women treated with ethanehydroxydiphosphonate (n = 12; mean age, 53.2 +/- 2 yr). Assignment to clinical groups was verified by plasma FSH and estradiol determinations. Lumbar spine bone mineral density was significantly higher in the premenopausal women group than in the three postmenopausal groups. Peripheral blood monocytes were cultured for 48 h with 20% autologous plasma, and after stimulation with lipopolysaccharides. IL-1, IL-6, and TNF alpha levels were measured by RIA in the monocyte surpernatants. The three cytokines were highly correlated to each other, IL-1 with IL-6 (r = 0.76; P < 0.001), IL-1 with TNF alpha (r = 0.89; P < 0.001), and IL-6 with TNF alpha (r = 0.89; P < 0.001). The mean levels of the three cytokines could not be compared because of the variations in the values. However, a trend toward lower levels in the three cytokines was noted in estrogen-treated women compared to the untreated postmenopausals. The bone-resorbing activity of monocyte supernatants, assessed by fetal long bone-resorbing assay, increased in untreated postmenopausal compared to that in premenopausal women (1.22 +/- 0.08 vs. 0.87 +/- 0.11; P < 0.05). In estrogen-treated patients, this activity decreased to premenopausal levels (0.89 +/- 0.04 vs. 0.87 +/- 0.11; P = NS). The resorbing activity was correlated to IL-1 (r = 0.28; P = 0.03), IL-6 (r = 0.52; P < 0.01), and TNF alpha (r = 0.48; P < 0.01). The addition of cytokine inhibitors and IL-1 receptor antagonist and TNF alpha antibodies to the supernatant bone culture medium induced a significant decrease in the calcium release. Those data show the involvement of several cytokines in the bone resorption process after estrogen deficiency.     

Effects of interferons on tumour necrosis factor alpha production from human keratinocytes

Interferons (IFNs) have been reported to have pleiotrophic effects including the ability to induce the production of other cytokines in several cell types. Tumour necrosis factor alpha (TNF-alpha) is pro-inflammatory cytokine a known to be produced by a variety of cells including human keratinocytes. In the present study, we sought to determine the effects of IFNs on TNF-alpha production from human keratinocytes. IFN-gamma (50-100 ng/ml) induced TNF-alpha production dose dependently, but no induction of TNF-alpha was observed with IFN-alpha or IFN-beta. Since in the epidermis cytokines often work with in a cascade fashion and keratinocytes are a source of primary cytokine, IL-1 alpha, whether combined treatment with IFN-gamma and IL-1 alpha had a synergistic effect on TNF-alpha production was examined. Combined treatment with IFN-gamma (100 ng/ml) and IL-1 alpha (10 ng/ml) induced 2-3-fold higher level of TNF-alpha than IL-1 alpha alone. These results suggest that IFN-gamma is a positive regulator for the production of TNF-alpha from human keratinocytes and likely to increase skin inflammation.     

Soluble tumor necrosis factor receptors are present in human vitreous and shed by retinal pigment epithelial cells

Tumor necrosis factor-alpha (TNF) has been implicated in the pathogenesis of several retinal diseases. Soluble forms of the TNF receptors, p55 (55 kDa) and p75 (75 kDa), have recently been identified in biological fluids and may regulate TNF activity. The potential biological significance of these receptors for the human retina was examined by determining their presence in human vitreous and their release from eye cup explants in which the retina has been removed leaving an intact retinal pigment epithelium (HRPE). Normal human vitreous and conditioned medium from eye-cup HRPE explants demonstrated the presence of soluble p55 and p75. Soluble p55 was significantly more abundant than p75 in all vitreous samples (P < 0.03). Conditioned medium from eye-cup HRPE explants contained significantly more soluble p55 than p75 (P < 0.00002). Enzyme-linked immunosorbent assay showed the presence of soluble p55, and not p75, in conditioned medium from primary cultured HRPE cells. Activation of the protein kinase C pathway in these cells with the phorbol ester PMA significantly increased the release of soluble p55 (P < or = 0.001); whereas, pharmacological inhibition of protein kinase C with calphostin-C significantly decreased the shedding of p55 (P < or = 0.001). The results indicate that primary cultured HRPE cells shed p55 and regulate this shedding in part through the protein kinase C pathway. The presence of soluble TNF receptors within normal human vitreous and within conditioned medium from the eye-cup HRPE explant model suggests that these soluble receptors may have a biological function in the eye.     

Serial prognostic capabilities of electrocardiographic indices of infarcted and hibernating myocardium in predicting short- and long-term outcome following coronary artery bypass surgery

Concentrations and ex vivo production of interleukin 1 beta (IL-1), tumour necrosis alpha (TNF), interleukin 6 (IL-6), interleukin-1 receptor antagonist (IL-1RA) and TNF soluble receptors (sTNF-receptors, P55 and P75) were measured in bronchoalveolar lavage (BAL) fluid and blood in 23 HIV-seropositive (HIV+) patients with Pneumocystis carinii pneumonia (PCP) and compared with values found in healthy HIV-seronegative (HIV-) controls and asymptomatic HIV+ subjects. Concentrations of the proinflammatory cytokine IL-1 beta were increased in BAL fluid of HIV+ patients with PCP (184 +/- 47 pg mL-1) compared with undetectable levels in healthy control subjects (P = 0.0001). In plasma of these patients higher concentrations of the anti-inflammatory cytokine IL-1RA were found during acute PCP than after recovery (2.1 +/- 0.7 vs. 0.5 +/- 0.2 ng mL-1, P = 0.01). No correlations could be found between cytokine concentrations and clinical severity of the infection. Corticosteroid treatment did not influence cytokine concentrations in BAL or blood, nor did it suppress the production in alveolar cells. In whole-blood cultures, however, lipopolysaccharide (LPS)-stimulated production was significantly suppressed for IL-1 (1.3 vs. 5.5 ng mL-1, P = 0.009) and for IL-6 (0.6 vs. 2.5 ng mL-1, P = 0.01). The overall data show that in HIV+ patients with PCP (similar to what we had found previously in HIV-patients with PCP) proinflammatory cytokines are more prominently present in BAL, whereas anti-inflammatory reaction is predominant in the circulation.     

IFN-gamma-mediated control of Coxiella burnetii survival in monocytes: the role of cell apoptosis and TNF

The treatment of infectious diseases caused by intracellular bacteria, such as Q fever, may benefit from cytokines acting on macrophages. Monocytic THP-1 cells were infected with Coxiella burnetii, the etiological agent of Q fever, and then treated with IFN-gamma. While C. burnetii multiplied in untreated monocytes, IFN-gamma reduced bacterial viability after 24 h of treatment and reached maximum inhibition after 96 h. IFN-gamma also affected the viability of infected cells. Cell death resulted from apoptosis; occurring 24 h after the addition of IFN-gamma, it reached a maximum after 48 h and was followed by necrosis. Reactive oxygen intermediates were not required for C. burnetii killing, since monocytes from patients with chronic granulomatous disease were microbicidal in response to IFN-gamma. The role of cytokines was also investigated. IFN-gamma elicited a moderate release of IL-1beta in infected monocytes. Moreover, the IL-1 receptor antagonist did not affect C. burnetii survival, suggesting that IL-1beta was not involved in the bacterial killing induced by IFN-gamma. TNF was involved in IFN-gamma-induced killing of C. burnetii and cell death. IFN-gamma induced mRNA expression and sustained secretion of TNF. Neutralizing Abs to TNF as well as Abs directed against TNF receptors I and II, significantly prevented IFN-gamma-dependent killing of C. burnetii and cell death. These results suggest that IFN-gamma promotes the killing of C. burnetii in monocytes through an apoptotic mechanism mediated in part by TNF.