The release of soluble p55 TNF receptor from U937 cells studied by a new p55 immunoassay

Effect of thalidomide on cardiac remodeling in chronic heart failure: results of a double-blind, placebo-controlled study

BACKGROUND

Inflammation and matrix degradation may play a pathogenic role in chronic heart failure (CHF), and therefore, we examined whether thalidomide, a drug with potential immunomodulating and matrix-stabilizing properties, could improve left ventricular (LV) function in patients with CHF secondary to idiopathic dilated cardiomyopathy (IDCM) or coronary artery disease (CAD).

METHODS AND RESULTS

Fifty-six patients with CHF and an LV ejection fraction (LVEF) <40% who were already on optimal conventional cardiovascular treatment were randomized to thalidomide (25 mg QD increasing to 200 mg QD) or placebo and followed up for 12 weeks. Our main findings were as follows: (1) During thalidomide treatment but not during placebo, there was a marked increase in LVEF (&7 EF units) along with a significant decrease in LV end-diastolic volume and heart rate. (2) This improvement in LVEF was accompanied by a decrease in matrix metalloproteinase-2 without any changes in its endogenous tissue inhibitor, suggesting a matrix-stabilizing net effect. (3) Thalidomide also induced a decrease in total neutrophil count and an increase in plasma levels of tumor necrosis factor-alpha, suggesting both proinflammatory and antiinflammatory effects. (4) The effect of thalidomide on LVEF was more marked in IDCM than in CAD, possibly partly reflecting that the former group was able to tolerate a higher thalidomide dosage.

CONCLUSIONS

Although our results must be confirmed in larger studies that also examine the effects on morbidity and mortality, our findings suggest a role for thalidomide in the management of CHF in addition to traditional cardiovascular medications.

Expression of chromogranin A and somatostatin receptors in pancreatic AR42J cells

The exocrine pancreatic cell line AR42J is also known to display some neuroendocrine (NE) features. We have extended this fact by showing that AR42J cells express mRNA of chromogranin A (CgA), display immunoreactivity (IR) to CgA, and secrete its cleavage product pancreastatin. A sparse occurrence of typical NE secretion granules, together with only a faint IR to conventional NE markers, indicates that the NE cells are of a poorly differentiated type. CgA promoter reporter plasmid experiments showed that gastrin, epidermal growth factor, and phorbol 12-myristate 13-acetate, induce upregulation of CgA after 24 h. By RT-PCR, it was found that AR42J expresses all of the five subtypes of the somatostatin (SST) receptor (SSTR) family, except SSTR4. The existence of functional SSTRs was confirmed by showing that the SST analog octreotide could inhibit gastrin-induced proliferation. Thus, the AR42J cell line may function as a valuable experimental model to study the regulation of CgA and SSTRs in poorly differentiated NE tumor cells.

Inflammatory mediators in umbilical plasma from neonates who develop early-onset sepsis

OBJECTIVES

To study whether early-onset neonatal sepsis is associated with a prenatal immune response with elevated umbilical plasma levels of inflammatory mediators, and to study whether mediator levels may be helpful in identifying infected neonates.

SETTING

Nested case-control study.

METHODS

Cord blood was sampled from 7,073 consecutively delivered neonates. After review of the medical records, neonates suspected to suffer from infection were classified as infected (n = 52) or noninfected but sick controls (n = 33). We also included a group of healthy controls (n = 99). Umbilical plasma levels of tumour necrosis factor-alpha (TNFalpha), interleukin (IL)-1beta, IL-6, IL-8, soluble TNF receptors (p55 and p75), IL-1 receptor antagonist (IL-1RA) and C-reactive protein were measured by immunoassays.

RESULTS

Infected neonates had higher levels of TNFalpha, IL-1beta, IL-6, IL-8, p55, p75 and IL-1RA than healthy controls (all p < 0.01). Among preterm infants (GA <37 weeks), those with infection (n = 11) had higher levels of IL-1beta, IL-6, IL-8, p55 and p75 than noninfected sick controls (n = 13) (all p < 0.05), but among term infants, the infected did not differ from the noninfected sick controls. Receiver operator characteristic plots showed that IL-1beta, IL-6 and IL-8 identified preterm infected neonates accurately.

CONCLUSIONS

Early-onset neonatal sepsis is associated with a prenatal immune response with increased TNFalpha, IL-1beta, IL-6, IL-8, p55, p75 and IL-1RA levels in umbilical plasma. Among neonates who present symptoms suggestive of infection, cytokine levels may be helpful in identifying preterm, but not term infected individuals.

High level of fatigue in lymphoma patients treated with high dose therapy

With the success of high dose therapy supported by autologous bone marrow transplantation (ABMT) for malignant lymphomas, medical late-effects and secondary effects on subjective health, like fatigue, are of concern. Fatigue is poorly understood and correlates have been barely addressed. Health-related quality of life (HRQL), fatigue, and correlates to fatigue, including endocrinological status and serum levels of interleukin-6, tumor necrosis factor, and soluble tumor necrosis factor receptors, were investigated in a cross-sectional study of 33 lymphoma patients (median age 39 years) 4-10 years after ABMT. The survivors were compared to general population norms. Fatigue was highly prevalent, and females reported significantly more fatigue and impaired HRQL compared to males and the normal population. Gonadal dysfunction was found in the majority of the patients, but no statistically significant endocrinological or immunological associations with fatigue could be demonstrated. The high level of fatigue among female long-term survivors after ABMT may be related to the gonadal dysfunction, but further studies of possible mechanisms behind fatigue are necessary.

Effect of high- versus low-dose angiotensin converting enzyme inhibition on cytokine levels in chronic heart failure

OBJECTIVES

We examined the effect of long-term treatment with two doses of the angiotensin converting enzyme (ACE) inhibitor enalapril on various immunological variables in patients with chronic congestive heart failure (CHF).

BACKGROUND

Immunological mediators are increasingly recognized to play a pathogenic role in the pathophysiology of CHF. Whether ACE inhibitor therapy modifies immunological variables has not previously been investigated.

METHODS

Seventy-five patients (mean age 52 +/- 11 years) with CHF were randomized between low-(5 m g daily) and high-dose (40 mg daily) enalapril in a double-blind trial. Circulating levels of immunological parameters (i.e., proinflammatory cytokines, chemokines and adhesion molecules) were measured at baseline, at 10 weeks and at the end of the study (34 weeks).

RESULTS

All immunological parameters, except soluble interleukin (IL)-6 receptor, were increased in CHF compared with 21 healthy controls. During the study immunoreactive IL-6 levels decreased (p < 0.05) and soluble IL-6 receptor increased (p < 0.05) during high-dose but not during low-dose enalapril therapy. Furthermore, IL-6 bioactivity decreased only during the high-dose (p < 0.001), resulting in a significant difference in change during treatment between the two dosage groups (p < 0.001). This decrease in IL-6 bioactivity was significantly associated with decreased interventricular septum thickness as assessed by echocardiography (r = 0.56, p = 0.013). No other variables changed during treatment.

CONCLUSIONS

In patients with severe CHF, high-dose enalapril therapy is associated with a significant decrease in IL-6 activity. However, despite treatment with a high-dose ACE inhibitor, a persistent immune activation exists in these patients which may be of importance for the progression of CHF.

Cytokine network in congestive heart failure secondary to ischemic or idiopathic dilated cardiomyopathy

Inflammatory cytokines may play a pathogenic role in the development of congestive heart failure (CHF). Elevated circulating levels of inflammatory cytokines have been reported in CHF, but most studies have focused on only a few cytokine parameters. However, the activity of these cytokines are modulated by soluble cytokine receptors and cytokines with anti-inflammatory activities, and in the present study several of these interacting factors were examined simultaneously in 38 CHF patients with various degrees of heart failure and in 21 healthy controls. Patients with CHF had increased plasma concentrations of tumor necrosis factor (TNF)alpha, interleukin-6, soluble TNF receptors and the soluble interleukin-6 receptor, glycoprotein (gp)130. They also had elevated ratios of TNFalpha/soluble TNF receptors and interleukin-6/soluble gp130 as well as enhanced interleukin-6 bioactivity in serum, suggesting inflammatory net effects. In addition to raised circulating levels of inflammatory cytokines, CHF patients with severe heart failure also had abnormalities in the levels of anti-inflammatory cytokines, with decreased levels of transforming growth factor beta1 and inadequately raised interleukin-10 in relation to the elevated TNFalpha concentrations. This dysbalance between inflammatory and anti-inflammatory cytokines was also found in monocyte supernatants from CHF patients. The abnormalities in the cytokine network were most pronounced in patients with the most severe heart failure, and several of the immunologic parameters, in particular soluble gp130, were correlated with variables reflecting deranged hemodynamic status. The present study analyzing the complexity of the cytokine network in CHF, demonstrates profound disturbances in the levels of both inflammatory and anti-inflammatory mediators with a marked dysbalance favoring inflammatory effects.

Decreased bone formative and enhanced resorptive markers in human immunodeficiency virus infection: indication of normalization of the bone-remodeling process during highly active antiretroviral therapy

As cytokines and 1,25-dihydroxyvitamin D [1,25-(OH)2D] appear to have an important role in bone homeostasis, we examined the possibility that human immunodeficiency virus (HIV)-infected patients, characterized by enhanced levels of proinflammatory cytokines and 1,25-(OH)2D deficiency, have disturbed bone metabolism by analyzing serum markers of bone formation (osteocalcin) and bone resorption (C-telopeptide) in 73 HIV-infected patients. HIV-infected patients with advanced clinical and immunological disease and high viral load were characterized by increased C-telopeptide and particularly by markedly depressed osteocalcin levels. HIV-infected patients had enhanced activation of the TNF system. Serum concentrations of p55 and p75-TNF receptors were negatively correlated with osteocalcin, and p75-TNF receptor was positively correlated with C-telopeptide. HIV-infected patients with advanced disease also had decreased serum concentrations of 1,25-(OH)2D, but this parameter was not correlated with osteocalcin or C-telopeptide. During 24 months with highly active antiretroviral therapy there was a marked rise in serum osteolcalcin levels together with a profound fall in viral load and TNF components and a marked rise in CD4+ T cell counts. Also, there was a shift from no correlation to a significant correlation between osteocalcin and C-telopeptide levels during such therapy. The present study suggests disturbed bone formation and resorption during HIV infection. Our findings indicating synchronization of bone remodeling during highly active antiretroviral therapy may represent a previously unrecognized beneficial effect of such therapy and expand our knowledge of the interactions between cytokines and bone in the bone-remodeling process.

Increased serum concentrations of soluble tumor necrosis factor receptors p55 and p75 in early onset neonatal sepsis

Sepsis and pneumonia are major causes of morbidity and mortality in the neonatal period. The symptoms are variable and unspecific. So far, no reliable diagnostic test for neonatal infection has been found. In this study we measured serum levels of soluble tumor necrosis factor receptors (sTNFR) p55 and p75 in non-infected and infected neonates, and evaluated the diagnostic value of these mediators as tests for early detection of neonates with sepsis or pneumonia. Blood was collected on admission and after 3-4 days from 161 neonates consecutively admitted to the Neonatal Intensive Care Unit (NICU) during the first week of life. Twenty two neonates suffered from infection and 127 were classified as non-infected (controls). Samples were analyzed for p55 and p75, C-reactive protein (CRP) and white blood cell count with differential. Both preterm and term infected neonates had initially higher concentrations of p55 (both p <0.01) and p75 (p = 0.01 and p = 0.05, respectively) than controls. In non-infected neonates p55 levels decreased in the perinatal period, whereas p75 levels remained stable. Levels of both p55 and p75 decreased in neonates with infection during the perinatal period. CRP was a more specific parameter than p55 and p75 (CRP: 97%, p55: 65% and p75: 75%) whereas the sensitivity of all three parameters was at similar levels (CRP: 59%, p55: 70% and p75: 67%). We conclude that assessment of sTNFR may not improve accuracy in the diagnosis of early onset neonatal sepsis compared to the use of CRP.

TNF, IL-1, IL-6, IL-8 and soluble TNF receptors in relation to chorioamnionitis and premature labor

Inflammatory cytokines seem to play a key role in mechanisms initiating labor. Since cytokine levels are higher in preterm than in term labor, it has been hypothesized that labor-inducing effects of cytokines are inhibited by an upregulated production of cytokine antagonists, such as soluble cytokine receptors, at early stages of gestation. In this study, TNF, IL-1, IL-6, IL-8 and soluble TNF receptors (sTNFRs) were measured in amniotic fluid samples from a) 39 women in premature labor, b) 25 women who where not in labor but delivered prematurely, and c) 33 women in term labor. Fifty-four of the placentas from premature deliveries were evaluated for presence of histological chorioamnionitis. Chorioamnionitis was associated with increased levels of TNF, IL-1 and IL-6, whereas elevated IL-1, IL-6 and IL-8 concentrations were found in premature parturition with no signs of infection. Concentrations of sTNFR were lower in preterm than in term deliveries. The present study confirms the participation of inflammatory cytokines in parturition. Multivariate analysis suggests a dominant, role of IL-1 in the presence of chorioamnionitis, whereas IL-6 seems to be more important during idiopathic premature labor. TNFR data do not support the hypothesis that production of cytokine antagonists is upregulated prematurely to prevent partirution.

Dysregulation of Membrane-Bound Tumor Necrosis Factor-α and Tumor Necrosis Factor Receptors on Mononuclear Cells in Human Immunodeficiency Virus Type 1 Infection: Low Percentage of p75-Tumor Necrosis Factor Receptor Positive Cells in Patients With Advanced Disease and High Viral Load

The correlation of persistent tumor necrosis factor-α (TNF-α) activation with disease progression in patients infected with human immunodeficiency virus type 1 (HIV-1), suggests a role for TNF-α in the pathogenesis of HIV-1 infection. In the present study, we examined by flow cytometry the expression of membrane-bound (m) components of the TNF system in 33 HIV-1–infected patients and 12 healthy controls. While peripheral blood mononuclear cells (PBMC) from asymptomatic and symptomatic non-acquired immune deficiency syndrome (AIDS) patients showed a significantly increased percentage of mTNF-α+ and mTNF receptor (TNFR)+ cells compared with controls, this was not found in the AIDS group. Compared with healthy controls, AIDS patients had a significantly decreased percentage of both monocytes and lymphocytes expressing p75-TNFR. PBMC from AIDS patients showed a higher p75-TNFR mRNA level and a higher spontaneous release of soluble p75-TNFR than healthy individuals, suggesting enhanced cell surface turnover of this TNFR. The low expression of TNFRs on both lymphocytes and monocytes in the AIDS group was associated with high numbers of HIV-1 RNA copies in plasma, low numbers of CD4+ lymphocytes, and high serum levels of soluble TNFRs. AIDS patients had a decreased percentage of CD8+ lymphocytes expressing TNFRs compared with healthy controls. In contrast, these patients, as well as symptomatic non-AIDS patients, had an increased percentage of TNF-α+ and TNFRs+ cells among remaining CD4+ lymphocytes. The pattern of abnormalities seen in AIDS patients suggests a role for persistent activation of the TNF system in the accelerated CD4+ lymphocyte destruction, the enhanced HIV-1 replication, and the markedly impaired antimicrobial defense in advanced HIV-1-related disease.

Dysregulation of Membrane-Bound Tumor Necrosis Factor-α and Tumor Necrosis Factor Receptors on Mononuclear Cells in Human Immunodeficiency Virus Type 1 Infection: Low Percentage of p75-Tumor Necrosis Factor Receptor Positive Cells in Patients With Advanced Disease and High Viral Load

The correlation of persistent tumor necrosis factor-α (TNF-α) activation with disease progression in patients infected with human immunodeficiency virus type 1 (HIV-1), suggests a role for TNF-α in the pathogenesis of HIV-1 infection. In the present study, we examined by flow cytometry the expression of membrane-bound (m) components of the TNF system in 33 HIV-1–infected patients and 12 healthy controls. While peripheral blood mononuclear cells (PBMC) from asymptomatic and symptomatic non-acquired immune deficiency syndrome (AIDS) patients showed a significantly increased percentage of mTNF-α+ and mTNF receptor (TNFR)+ cells compared with controls, this was not found in the AIDS group. Compared with healthy controls, AIDS patients had a significantly decreased percentage of both monocytes and lymphocytes expressing p75-TNFR. PBMC from AIDS patients showed a higher p75-TNFR mRNA level and a higher spontaneous release of soluble p75-TNFR than healthy individuals, suggesting enhanced cell surface turnover of this TNFR. The low expression of TNFRs on both lymphocytes and monocytes in the AIDS group was associated with high numbers of HIV-1 RNA copies in plasma, low numbers of CD4+ lymphocytes, and high serum levels of soluble TNFRs. AIDS patients had a decreased percentage of CD8+ lymphocytes expressing TNFRs compared with healthy controls. In contrast, these patients, as well as symptomatic non-AIDS patients, had an increased percentage of TNF-α+ and TNFRs+ cells among remaining CD4+ lymphocytes. The pattern of abnormalities seen in AIDS patients suggests a role for persistent activation of the TNF system in the accelerated CD4+ lymphocyte destruction, the enhanced HIV-1 replication, and the markedly impaired antimicrobial defense in advanced HIV-1-related disease.

Evidence for exclusive role of the p55 tumor necrosis factor (TNF) receptor in mediating the TNF-induced collagenase expression by human dermal fibroblasts

The aim of this study was to examine the roles of the TNF receptors p55 and p75 in the TNF-enhanced expression of collagenase by human dermal fibroblasts. The agonistic p55 monoclonal antibody Htr9 and TNF induced production of similar amounts of collagenase. Polyclonal or monoclonal agonistic p75 antibodies failed to enhance collagenase production, and the antagonistic p75 antibody 5E12 did not inhibit TNF-enhanced expression of collagenase. This strongly suggests that p55, but not p75, is involved in TNF-induced production of collagenase. Cells continued to produce an elevated level of collagenase after the removal of TNF or Htr9. These data suggest that it may be useful to use specific inhibitors of collagenase rather than to block cytokine action directly in the treatment of diseases with chronic enhanced collagenolytic activity. A peptide of residues 36-62 of TNF previously reported to be chemotactic to leukocytes was also able to enhance the expression of collagenase activity by dermal fibroblasts. Thus, design of peptides with specific TNF effects may offer a novel approach for treatment of fibrotic disorders.

Modulation of tumor necrosis factor (TNF) receptor expression during monocytic differentiation by glucocorticoids

OBJECTIVE AND DESIGN

Regulation of tumor necrosis factor receptors by glucocorticoids was investigated during phorbol ester-induced monocytic differentiation.

MATERIALS AND TREATMENT

As model system the human monocytic cell lines U937 and THP-1, which express both types of TNF receptors (TNF-R60 and TNF-R80), were differentiated with tetradecanoyl phorbol-13-acetate (TPA, 5 x 10(-9) M) in the presence or absence of dexamethasone (10(-9) - 10(-6) M).

METHODS

Expression of TNF receptors was determined at the mRNA level by Northern blot analysis and at the protein level by FACS analysis.

RESULTS

During differentiation, TNF-R60 mRNA was down-regulated, whereas TNF-R80 mRNA levels were increased. Dexamethasone had no effect on TNF-R60 mRNA expression but attenuated TNF-R80 mRNA expression in both cell lines. Cell surface expression of TNF-R60 protein remained essentially unchanged during differentiation of THP-1 cells, whereas a rapid down-regulation of TNF-R80 was observed that was followed by a slow recovery. Surface expression of TNF-R80 was not affected by dexamethasone, whereas TNF-R60 expression was reduced by about 25%.

CONCLUSIONS

These results indicate differential regulation of the two types of TNF receptors at the mRNA and protein level during monocytic differentiation. Glucocorticoids interfered with mRNA expression of TNF-R80 and protein expression of TNF-R60, but the rather limited effect leaves the question of its functional relevance open. In contrast to other cytokine systems, TNF receptors do not appear to be major targets of glucocorticoid action.

Metalloproteases and serineproteases are involved in the cleavage of the two tumour necrosis factor (TNF) receptors to soluble forms in the myeloid cell lines U-937 and THP-1

The proteolytic processing of the two TNF receptors (TNF-R55 and TNF-R75) into soluble forms was investigated in the myeloid cell lines U-937 and THP-1. Phorbol myristate acetate (PMA) rapidly stimulated release of soluble forms of both TNF-receptors. Incubations were made with PMA and protease inhibitors directed against different target protease groups. The serineprotease inhibitors TPCK and dichloroisocoumarin and the metalloprotease inhibitor 1,10-phenanthroline reduced PMA-induced release of both soluble receptor forms with about 60-70%. Furthermore, 1,10-phenanthroline also reduced PMA-induced down-regulation of TNF-receptors in both cell lines as judged by TNF-binding to cells. Reduced down-regulation and TNF-receptor shedding by 1,10-phenanthroline was reversed by Zn2+, indicating involvement of a Zn(2+)-dependent metalloprotease. Thus, both serine proteases and metalloproteases are involved in the processing of TNF-receptors.

Polymorphonuclear granulocytes enhance lipopolysaccharide-induced soluble p75 tumor necrosis factor receptor release from mononuclear cells

Lipopolysaccharide (LPS), a part of the Gram-negative bacteria cell wall, is a potent inducer of tumor necrosis factor (TNF). TNF is an important mediator in Gram-negative infections such as meningococcal septic shock, but its harmful action can be prevented by the natural occurring soluble (s) TNF receptors (sTNFR) sp55 and sp75. In this study, the effect of LPS on release of sTNFR was investigated. First, we found a selective increase in human whole-blood sp75 TNFR levels following LPS stimulation, accompanied by no increase in sp55. Separating the different blood cell populations, mononuclear cells (PBMC) selectively released sp75 upon LPS stimulation, while LPS induced a minor increase in sp75 release from polymorphonuclear granulocytes. Interestingly, in co-cultures of PBMC and granulocytes, the release of LPS-induced sp75 TNFR was enhanced. Second, adherent monocytes were also found to selectively release sp75 TNFR upon LPS stimulation, where Neisseria meningitidis LPS was found to be 100-1000 times more potent in inducing sp75 release than Escherichia coli LPS. Using flow cytometry, the monocyte membrane distribution of both TNFR were found to be increased after LPS stimulation. Third, human umbilical vein endothelial cells selectively released sp55 TNFR after stimulation with LPS. We conclude that mononuclear and endothelial cells might be the main sources of soluble p75 and p55 TNFR, respectively, observed in Gram-negative sepsis, although these receptors are released in vivo more rapidly than they are in vitro.

Soluble tumor necrosis factor receptor in serum and urine throughout normal pregnancy and at delivery

PROBLEM

To determine the concentration of the two soluble tumor necrosis factor receptors (sTNFR), sp55 and sp75, in healthy pregnant women.

METHOD

Serum and urine samples were longitudinally collected from a group of pregnant women (N = 53) five times throughout pregnancy. Maternal and umbilical sera were obtained from some of the deliveries (N = 31). The samples were analysed using ELISA based on two monoclonal antibodies (IV4E and 3H5) against the soluble tumor necrosis factor receptors (sp55 and sp75).

RESULTS

Serum concentration of sp55 and sp75 were increased in pregnant women compared to that of nonpregnant controls. Concentration of both sTNFRs increased towards term. Labor was associated with further increase of sp55. Concentrations of sp55 and sp75 in umbilical serum were significantly higher than those of maternal serum. Significant correlations were observed between maternal and umbilical sTNFR concentrations.

CONCLUSIONS

The current study suggests that pregnancy is associated with an activation of mechanisms regulating the biological activities of TNF.

Soluble tumour necrosis factor receptors, tumour necrosis factor and interleukin-6 in serum in granulocytopenic patients with fever

Serum levels of TNF, IL-6 and soluble TNF receptors p55 and p75 (sTNFR-p55 and sTNFR-p75) were examined in 14 patients with acute myeloid leukaemia during 43 courses of chemotherapy. The patients experienced 30 episodes of fever which occurred during granulocytopenia (defined as granulocyte counts < 0.2 x 10(9)/l) and six fever episodes when granulocyte counts were > 1.0 x 10(9)/l. Febrile episodes were classified as microbiologically defined infection, clinically defined infection, and unexplained fever. Levels of bioactive IL-6 and immunoreactive TNF increased in response to fever during granulocytopenia, whereas bioactive TNF was not detected in any sample in this study. During granulocytopenia, both sTNFR rose significantly in microbiologically defined infection (P < 0.01 for sTNFR-p55 and P < 0.05 for sTNFR-p75), but not in the other two categories. The ratio of sTNFR-p55 to sTNFR-p75 was higher during febrile periods in granulocytopenia than in a non-granulocytopenic situation with granulocyte counts > 1.0 x 10(9)/l (P < 0.01). We conclude that granulocytopenia affects release of the two sTNFR differently during febrile periods, and that release of sTNFR-p75 in response to fever is reduced during granulocytopenia, suggesting a role for the granulocytes in systemic release of sTNFR-p75.

Activation of tumor necrosis factor--alpha system in HIV-1 infection: association with markers of immune activation

The relationships between serum levels of soluble tumor necrosis factor receptors (sTNFRs) and other prognostic and immunological parameters in different immunological subgroups of 64 HIV-1 infected patients were studied. In the patient group as a whole, the raised serum levels of sTNFRs were significantly inversely correlated to the numbers of CD4+ and CD8+ lymphocytes and significantly positively correlated with serum levels of neopterin, HIV-1 p24 antigen and the soluble CD8/CD8+ lymphocyte ratio. However, when the patients were classified into three separate immunological subgroups according to the numbers of CD4+ lymphocytes, only serum levels of neopterin were significantly correlated to levels of sTNFRs in all the defined immunological subgroups. These results indicate that HIV-1 infection is associated with a persistent and chronic immune activation in the TNF system manifested by raised serum levels of sTNFRs, which may reflect sustained activation of the immune system particularly in monocytes/macrophages. Further, these results confirm that, when comparing immunological and virological parameters in HIV-1 infection, different results may be obtained in different immunological subgroups of patients.

Increased levels of cytokines and cytokine activity modifiers in normal pregnancy

Accumulating evidence suggests that cytokines are major participants in human reproduction. Cytokines may have beneficial or negative influence on pregnancy outcome, depending on the cytokine level present. Thus, successful reproduction appears to depend on a tight regulation of cytokine activities. The present study raised the question whether normal pregnancy is associated with an activation of native cytokine buffer mechanisms. Soluble interleukin 6 receptors (IL-6Rs) and soluble interleukin 1 receptor antagonists (IL-1RAs) may modify the activity of IL-6 and IL-1, respectively. The production of soluble IL-6R and IL-1RA in pregnancy was studied by assessing the IL-6R and IL-1RA concentrations in serum samples from healthy pregnant women at different gestational ages. At delivery, both maternal and umbilical blood was obtained. Concentrations of IL-6 and IL-1 in the samples were determined to study the influence of cytokines on the activity level of the corresponding buffer mechanism. Serum levels of both IL-6R and IL-1RA were increased in pregnant women, as were levels of IL-6 and IL-1. Cytokine levels did not demonstrate a significant correlation with the concentration of the corresponding activity modifier. IL-1RA and IL-6 increased with gestational age and with labor activity. A significant correlation was observed between the levels of IL-6 and IL-1RA.

Involvement of the tumor necrosis factor receptor p75 in mediating cytotoxicity and gene regulating activities

Using agonistic antibodies (Ab) we have examined whether the 75-kDa chain of the tumor necrosis factor receptor (p75 TNFR) is capable of mediating cytotoxic response and gene regulation alone or in cooperation with p55 TNFR. Addition of an anti-p75 TNFR polyclonal antiserum or anti-p75 monoclonal antibody (mAb) plus anti-immunoglobulin (Ig) led to cytotoxic response of human KYM-1 rhabdomyosarcoma cells. Anti-p75 mAb alone had no effect pointing out the importance of strong receptor stimulation for signal transduction into the cell. Simultaneous triggering of both the p55 and p75 TNFR by agonistic Ab resulted in additive cytotoxic action on KYM-1 cells. The anti-p75 mAb 3H5, directed to a non-TNF binding site on the human p75 TNFR, was used to confirm further the ability of the p75 TNFR to potentiate p55 TNFR-mediated cell death. While exhibiting no cytotoxicity by its own, 3H5 significantly augmented the cytotoxic effect of the anti-p55 mAb htr9 towards KYM-1 cells. Neither the anti-p75 TNFR antiserum nor anti-p75 mAb were cytotoxic for human U937 cells suggesting that the cytolysis resulting from p75 TNFR cross-linking is cell specific. Noteworthy, stimulation of the p75 TNFR with mAb plus anti-Ig or polyclonal antiserum led to a marked enhancement of the p55 TNFR-induced U937 cell death, indicating collaboration between the two TNFR in induction of cytotoxicity also in this cell line. However, 3H5 mAb did not affect the ability of anti-p55 mAb to lyse U937 cells. Altogether, these data demonstrate the difference between KYM-1 and U937 cell lines with respect to the role for the p75 TNFR in mediating cytotoxicity. Both TNFR were found to mediate cytomegalovirus (CMV) promoter activation in human SW480T-beta Gal cells and nuclear transcription factor kappa B (NF-kappa B) induction in this cell line as well as in KYM-1 cells. It was demonstrated for the first time that independent stimulation of both TNFR resulted in an additive effect on the CMV promoter activation and induction of the NF-kappa B. Taken together, these results indicate that the p75 TNFR induces cytotoxicity in a cell-specific manner and potentiates p55 TNFR-mediated cytotoxic response and gene regulation.