Expression of iron transport proteins divalent metal transporter-1, Ferroportin-1, HFE and transferrin receptor-1 in human monocyte-derived dendritic cells

Iron is essential for cell survival and regulates many cell functions. In the context of the immune response, iron-related metabolism is tightly controlled in activated lymphocytes as well as in cells of the innate immunity. More precisely, for dendritic cells (DCs), which are the key cell type in the development of a specific immune response, the importance of iron absorption was recently unravelled by showing that depletion of iron inhibits the maturation of DCs. On this basis, we studied in detail the expression of iron transport proteins and HFE in DCs. We found that iron uptake in this cell type is mediated by divalent-metal transporter 1 (DMT1) and transferrin receptor-1 (TfR) whereas Ferroportin-1 is very weakly expressed. HFE that regulates TfR's activity is also detected at the mRNA level. The expression of DMT1 and HFE barely varies upon endotoxin-induced maturation but TfR is up-regulated and the iron export molecule Ferroportin-1 is down-regulated. As opposed to MHC class II molecules, the intracellular localization of TfR is not changed during maturation. Our results indicate that the uptake of iron during DCs development and maturation is mediated by a strong expression of iron-uptake molecules such as DMT1 and TfR as well as a down-regulation of iron export molecules such as Ferroportin-1.

Direct recognition by alphabeta cytolytic T cells of Hfe, a MHC class Ib molecule without antigen-presenting function

Crystallographic analysis of human Hfe has documented an overall structure similar to classical (class Ia) MHC molecules with a peptide binding groove deprived of ligand. Thus, to address the question of whether alphabeta T cells could recognize MHC molecules independently of bound ligands, we studied human and mouse Hfe interactions with T lymphocytes. We provide formal evidence of direct cytolytic recognition of human Hfe by mouse alphabeta T cell receptors (TCR) in HLA-A*0201 transgenic mice and that this interaction results in ZAP-70 phosphorylation. Furthermore, direct recognition of mouse Hfe molecules by cytotoxic T lymphocytes (CTLs) was demonstrated in DBA/2 Hfe knockout mice. These CTLs express predominantly two T cell antigen receptor alpha variable gene segments (AV6.1 and AV6.6). Interestingly, in wild-type mice we identified a subset of CD8+ T cells positively selected by Hfe that expresses the AV6.1/AV6.6 gene segments. T cell antigen receptor recognition of MHC molecules independently of bound ligand has potential general implications in alloreactivity and identifies in the Hfe case a cognitive link supporting the concept that the immune system could be involved in the control of iron metabolism.

Single point mutations in the zinc finger motifs of the human immunodeficiency virus type 1 nucleocapsid alter RNA binding specificities of the gag protein and enhance packaging and infectivity

A specific interaction between the nucleocapsid (NC) domain of the Gag polyprotein and the RNA encapsidation signal (Psi) is required for preferential incorporation of the retroviral genomic RNA into the assembled virion. Using the yeast three-hybrid system, we developed a genetic screen to detect human immunodeficiency virus type 1 (HIV-1) Gag mutants with altered RNA binding specificities. Specifically, we randomly mutated full-length HIV-1 Gag or its NC portion and screened the mutants for an increase in affinity for the Harvey murine sarcoma virus encapsidation signal. These screens identified several NC zinc finger mutants with altered RNA binding specificities. Furthermore, additional zinc finger mutants that also demonstrated this phenotype were made by site-directed mutagenesis. The majority of these mutants were able to produce normal virion-like particles; however, when tested in a single-cycle infection assay, some of the mutants demonstrated higher transduction efficiencies than that of wild-type Gag. In particular, the N17K mutant showed a seven- to ninefold increase in transduction, which correlated with enhanced vector RNA packaging. This mutant also packaged larger amounts of foreign RNA. Our results emphasize the importance of the NC zinc fingers, and not other Gag sequences, in achieving specificity in the genome encapsidation process. In addition, the described mutations may contribute to our understanding of HIV diversity resulting from recombination events between copackaged viral genomes and foreign RNA.

The non-classical HLA class I molecule HFE does not influence the NK-like activity contained in fresh human PBMCs and does not interact with NK cells

In humans, four beta2-microglobulin-associated non-classical class I molecules are encoded in the MHC: HLA-E, -F, -G and -H. Three of them (HLA-E, -F and -G) were shown to inhibit NK activity. On the contrary, the fourth one, HLA-H, named HFE after it was found to be mutated in patients suffering from inherited hemochromatosis, has been shown to be involved only in the regulation of iron uptake. We tested the capacity of HFE to affect (enhance or reduce) specifically the NK activity contained in non-manipulated fresh human PBMCs. We showed that HFE expression by target cells does not affect their killing by the NK-like activity contained in PBMCs. Moreover, using fluorescent HFE tetramers, we could confirm that blood NK cells as well as blood gammadelta T cells do not bind HFE. Altogether, our data indicate that HFE does not affect the NK activity contained in the PBMCs.

The conserved carboxy terminus of the capsid domain of human immunodeficiency virus type 1 gag protein is important for virion assembly and release

The retroviral Gag precursor plays an important role in the assembly of virion particles. The capsid (CA) protein of the Gag molecule makes a major contribution to this process. In the crystal structure of the free CA protein of the human immunodeficiency virus type 1 (HIV-1), 11 residues of the C terminus were found to be unstructured, and to date no information exists on the structure of these residues in the context of the Gag precursor molecule. We performed phylogenetic analysis and demonstrated a high degree of conservation of these 11 amino acids. Deletion of this cluster or introduction of various point mutations into these residues resulted in significant impairment of particle infectivity. In this cluster, two putative structural regions were identified, residues that form a hinge region (353-VGGP-356) and those that contribute to an alpha-helix (357-GHKARVL-363). Overall, mutations in these regions resulted in inhibition of virion production, but mutations in the hinge region demonstrated the most significant reduction. Although all the Gag mutants appeared to have normal Gag-Gag and Gag-RNA interactions, the hinge mutants were characterized by abnormal formation of cytoplasmic Gag complexes. Gag proteins with mutations in the hinge region demonstrated normal membrane association but aberrant rod-like membrane structures. More detailed analysis of these structures in one of the mutants demonstrated abnormal trapped Gag assemblies. These data suggest that the conserved CA C terminus is important for HIV-1 virion assembly and release and define a putative target for drug design geared to inhibit the HIV-1 assembly process.

Natural HLA class I polymorphism controls the pathway of antigen presentation and susceptibility to viral evasion

HLA class I polymorphism creates diversity in epitope specificity and T cell repertoire. We show that HLA polymorphism also controls the choice of Ag presentation pathway. A single amino acid polymorphism that distinguishes HLA-B*4402 (Asp116) from B*4405 (Tyr116) permits B*4405 to constitutively acquire peptides without any detectable incorporation into the transporter associated with Ag presentation (TAP)-associated peptide loading complex even under conditions of extreme peptide starvation. This mode of peptide capture is less susceptible to viral interference than the conventional loading pathway used by HLA-B*4402 that involves assembly of class I molecules within the peptide loading complex. Thus, B*4402 and B*4405 are at opposite extremes of a natural spectrum in HLA class I dependence on the PLC for Ag presentation. These findings unveil a new layer of MHC polymorphism that affects the generic pathway of Ag loading, revealing an unsuspected evolutionary trade-off in selection for optimal HLA class I loading versus effective pathogen evasion.

Mouse HFE inhibits Tf-uptake and iron accumulation but induces non-transferrin bound iron (NTBI)-uptake in transformed mouse fibroblasts

Iron-uptake and storage are tightly regulated to guarantee sufficient iron for essential cellular processes and to prevent the production of damaging free radicals. A non-classical class I MHC molecule, the hemochromatosis factor (HFE), has been shown to regulate iron metabolism, potentially via its interaction with the transferrin receptor. Whereas, the effect of human HFE (hHFE) on transferrin/transferrin receptor association, as well as on transferrin receptor recycling and the level of cellular iron pools in various cell lines was analyzed, very little is known about the mouse HFE (mHFE) protein. In the following study, our aim was to analyze in more detail the function of mHFE. Surprisingly, we observed that over-expression of mHFE, but not of hHFE, in a mouse transformed cell line, results in a most significant inhibition of transferrin-uptake which correlated with apoptotic cell death. mHFE inhibited transferrin-uptake immediately following transfection and this inhibition persisted in the surviving stable transfectants. Concomitantly, cellular iron derived from transferrin-iron uptake was dramatically limited. The activation of a non-transferrin bound iron-uptake pathway that functions in the stable mHFE-transfected clones could explain their normal growth curves and survival. The hypothesis that iron starvation can induce iron-uptake by a novel transferrin-independent pathway is discussed.

Manipulation of Iron to Determine Survival: Competition Between Host and Pathogen

Iron is an essential nutrient that can determine cellular survival. Many organisms have evolved sophisticated mechanisms for iron uptake and transport to support their growth. The dual dependence on iron of both the host and invading pathogen initiates a competition for this nutrient following infection. Microorganisms have developed various strategies to acquire iron from the host. These are counter-balanced by an iron-withholding strategy that the host deploys as part of its defense system. This strategy, involving many iron-regulatory proteins, mediates iron depletion at the mucosal surfaces, in the extracellular environment, and within the cells. Iron is sequestered into storage by the host in order to deprive the pathogens of this factor and to prevent their proliferation. This system can be compromised. In particular, new evidence is emerging that suggests that viruses are able to specifically target and regulate proteins involved in iron homeostasis. This review focuses on the procedures employed by the host and viruses to regulate iron as a means of defense and survival, respectively.

Tranferrins receptor association and endosomal localization of soluble HFE are not sufficient for regulation of cellular iron homeostasis

Iron uptake and storage are tightly regulated to guarantee sufficient iron for essential cellular processes and to prevent the production of damaging free radicals. A non-classical class I MHC molecule, the hemochromatosis factor HFE, has been shown to regulate iron metabolism, potentially via its direct interaction with the transferrin receptor (TfR). In this study, we demonstrate that a soluble beta2microglobulin-HFE monochain (sHFE) folds with beta2microglobulin (beta2m) and associates with the TfR, indicating that the transmembrane and cytoplasmic domains are not necessary for assembly and trafficking through the ER-Golgi network. We also demonstrate human TfR-specific uptake and accumulation of extracellular sHFE by treated cells. The sHFE localized to the endosomal compartment albeit we observed variation in the time taken for endosomal trafficking between different cell types. The sHFE monochain was effective in reducing Tf uptake into cells, however this did not correlate to any changes in TfR or ferritin synthesis, in contrast to the HFE-induced increase and decrease of TfR and ferritin, respectively. These findings of incongruent sHFE activity suggest that either variation in affinity binding of sHFE to TfR prevents efficient modulation of iron-regulated proteins or that HFE has multiple functions some of which may be independent of TfR but dependent on interactions within the endosomal compartment for effective modulation of iron metabolism.

A single viral protein HCMV US2 affects antigen presentation and intracellular iron homeostasis by degradation of classical HLA class I and HFE molecules

HFE is a nonclassical class I molecule that associates with beta 2-microglobulin (beta 2m) and with the transferrin receptor. HFE accumulates in transferrin-containing endosomes, and its overexpression in human cell lines correlates with decreased transferrin receptor (TFR)-mediated iron uptake and decreased intracellular iron pools. A mutation that interferes with proper folding and assembly of HFE complexes results in a severe iron-overload disease hereditary hemochromatosis. We previously suggested that viruses could also interfere with iron metabolism through the production of proteins that inactivate HFE, similarly to classical class I proteins. In particular, we demonstrated in a transient expression system that human cytomegalovirus (HCMV) US2 targeted HFE for proteasomal degradation. Here we demonstrate that the stable expression of HCMV US2 in HEK 293 cells constitutively expressing HFE leads to loss of HFE expression both intracellularly and on the cell surface, and the significant reduction of classical class I expression. Both HFE and classical class I molecules are targeted to degradation via a similar pathway. This HCMV US2-mediated degradation of HFE leads to increased intracellular iron pools as indicated by reduced synthesis of TfR and increased ferritin synthesis. Whether this interference with regulation of iron metabolism potentiates viral replication and/or promotes damage of HCMV-infected tissues remains to be determined. Nevertheless, the deleterious effect of US2 on the expression of HFE and classical class I major histo-compatibility complexes (MHC) provides HCMV with an efficient tool for altering cellular metabolic functions, as well as supporting the escape of virus-infected cells from cytotoxic T lymphocyte (CTL)-mediated immune responses.

Elevated interleukin-8 concentrations in cervical secretions are associated with preterm labour

The aim of this study was to assess the potential clinical utility of interleukin-8 (IL-8) present in cervical secretions as a marker of preterm labour and delivery. Samples of cervical mucus from 91 pregnant women were assessed for the presence and concentration of IL-8. Two samples were collected (at 18 +/- 2 and 28 +/- 2.5 weeks of gestation) and correlated with cervicovaginal microbiology and cervical length, as measured by transvaginal ultrasound. The IL-8 concentration at 28/40 was significantly higher in women who went on to deliver preterm (p < 0.01), and there was a greater than five-fold increase from 18 to 28 weeks in 6/7 of these women.

Quantitative and qualitative influences of tapasin on the class I peptide repertoire

Tapasin is critical for efficient loading and surface expression of most HLA class I molecules. The high level surface expression of HLA-B*2705 on tapasin-deficient 721.220 cells allowed the influence of this chaperone on peptide repertoire to be examined. Comparison of peptides bound to HLA-B*2705 expressed on tapasin-deficient and -proficient cells by mass spectrometry revealed an overall reduction in the recovery of B*2705-bound peptides isolated from tapasin-deficient cells despite similar yields of B27 heavy chain and beta(2)-microglobulin. This indicated that a proportion of suboptimal ligands were associated with B27, and they were lost during the purification process. Notwithstanding this failure to recover these suboptimal peptides, there was substantial overlap in the repertoire and biochemical properties of peptides recovered from B27 complexes derived from tapasin-positive and -negative cells. Although many peptides were preferentially or uniquely isolated from B*2705 in tapasin-positive cells, a number of species were preferentially recovered in the absence of tapasin, and some of these peptide ligands have been sequenced. In general, these ligands did not exhibit exceptional binding affinity, and we invoke an argument based on lumenal availability and affinity to explain their tapasin independence. The differential display of peptides in tapasin-negative and -positive cells was also apparent in the reactivity of peptide-sensitive alloreactive CTL raised against tapasin-positive and -negative targets, demonstrating the functional relevance of the biochemical observation of changes in peptide repertoire in the tapasin-deficient APC. Overall, the data reveal that tapasin quantitatively and qualitatively influences ligand selection by class I molecules.

Distinct functions of tapasin revealed by polymorphism in MHC class I peptide loading

Peptide assembly with class I molecules is orchestrated by multiple chaperones including tapasin, which bridges class I molecules with the TAP and is critical for efficient Ag presentation. In this paper, we show that, although constitutive levels of endogenous murine tapasin apparently are sufficient to form stable and long-lived complexes between the human HLA-B*4402 (B*4402) and mouse TAP proteins, this does not result in normal peptide loading and surface expression of B*4402 molecules on mouse APC. However, increased expression of murine tapasin, but not of the human TAP proteins, does restore normal cell surface expression of B*4402 and efficient presentation of viral Ags to CTL. High levels of soluble murine tapasin, which do not bridge TAP and class I molecules, still restore normal surface expression of B*4402 in the tapasin-deficient human cell line 721.220. These findings indicate distinct roles for tapasin in class I peptide loading. First, tapasin-mediated bridging of TAP-class I complexes, which despite being conserved across the human-mouse species barrier, is not necessarily sufficient for peptide loading. Second, tapasin mediates a function which probably involves stabilization of empty class I molecules and which is sensitive to structural compatibility of components within the loading complex. These discrete functions of tapasin predict limitations to the study of HLA molecules across some polymorphic and species barriers.

Interleukin-8 release from human gestational tissue explants: effects of gestation, labor, and chorioamnionitis

Interleukin-8 (IL-8) is a chemotactic cytokine that has been implicated in the process of human parturition, including the processes of cervical ripening and rupture of fetal membranes. In this study, the in vitro release of IL-8 from human amnion, choriodecidua, and placenta tissues obtained before and after spontaneous labor onset both at term and preterm, was assessed. The effect of chorioamnionitis on IL-8 release was also established. All tissue explants examined released IL-8; however, IL-8 release from choriodecidual explants was significantly (p < 0.02) greater than that observed from amnion and placenta. Furthermore, choriodecidual IL-8 release was significantly (p < 0.001) greater from term tissues (850 +/- 134.4 ng/mg DNA, n = 18) than from preterm tissues (458 +/- 68.8 ng/mg DNA, n = 17). Spontaneous onset of labor, irrespective of the eventual mode of delivery, was not associated with any significant changes in IL-8 release from human gestational tissues compared to not-in-labor tissues, both at term and preterm. IL-8 release from gestational tissues was not significantly different in the absence or presence of chorioamnionitis. These data are in contrast to the previously reported stimulatory effects of bacterial endotoxin on IL-8 release from human gestational tissues. The data are consistent, however, with the suggestion that IL-8 release is an early event in chorioamnionitis that precedes the appearance of clinically overt symptoms.

Interleukin-8 release from human gestational tissue explants: the effects of lipopolysaccharide and cytokines

Interleukin (IL)-8 is a chemotactic cytokine that has been implicated in the etiology of infection-induced and normal human labor. In particular, IL-8 has been implicated in the processes of cervical ripening and rupture of fetal membranes because of its role in neutrophil activation and release of cellular matrix remodeling enzymes. In this study, we tested the hypotheses that IL-8 is released locally in the intrauterine environment from human amnion, choriodecidua, and placenta, and that IL-8 release from these tissues is increased by bacterial endotoxin, lipopolysaccharides (LPS), and inflammatory cytokines. IL-8 was released from human amnion, choriodecidual, and placental explants, with choriodecidua demonstrating the most abundant release. IL-8 release was significantly (multiple analysis of variance, p < 0.05) increased by LPS in a time- and dose-dependent manner from both choriodecidual and placental explants, but not from amnion explants. In addition, IL-1alpha (0.28 nM) and tumor necrosis factor alpha (TNFalpha, 10 nM) significantly (Student's t-test, p < 0.05) increased IL-8 release from placental explants 2- to 3-fold. These studies establish that the amnion, choriodecidua, and placenta are a source of IL-8 and demonstrate tissue-specific and differential regulation of IL-8 release by LPS, IL-1alpha, and TNF-alpha. These data support a role for IL-8 in a cascade of inflammatory events initiated by an intrauterine infection and resulting in activation of the labor process.

Tumor necrosis factor-beta in human pregnancy and labor

The aims of this study were to determine tumor necrosis factor-beta (TNF-beta) concentration profiles in peripheral venous plasma and amniotic fluid during pregnancy and at the time of labor and to characterise TNF-beta mRNA expression and TNF-beta release from human gestational tissues. In addition, we investigated the expression of TNF-beta binding protein, lymphotoxin-beta (LT-beta), in human gestational tissues. The mean (+/-S.E.M.) TNF-beta concentrations in maternal plasma (TIL, 78 +/- 12 pg/ml, n = 7 vs. TNIL, 304 +/- 88 pg/ml, n = 7) and amniotic fluid (TIL, 8 +/- 5 pg/ml, n = 6 vs. TNIL, 73 +/- 20 pg/ml, n = 20) were significantly (P < 0.05) decreased in association with term labor-onset (TIL) compared to term not-in-labor (TNIL). TNF-beta concentration in maternal plasma and amniotic fluid did not change significantly either with preterm labor (PIL), or during pregnancy. Group-matched comparison of maternal plasma and amniotic fluid TNF-beta concentrations demonstrated that amniotic fluid TNF-beta concentrations were 6-8 fold lower than maternal plasma TNF-beta concentrations. Furthermore, no detectable TNF-beta was secreted from cultured human amniotic, choriodecidual and placental explants. Although, TNF-beta mRNA was detected in amnion, choriodecidual and placenta, LT-beta was similarly expressed in these tissues, suggesting that TNF-beta may be cell membrane bound. These data demonstrate that TNF-beta is present at low levels within the intrauterine environment and may suggest that TNF-beta is specifically inhibited at the maternal-fetal interface.

Labour-associated increase in interleukin-1 alpha release in vitro by human gestational tissues

The aims of this study were to investigate the concentration and release of interleukin-1 alpha (IL-1 alpha) at the time of human term labour, and to study the regulation of IL-1 alpha release from human gestational tissue explants by bacterial endotoxin. Immunoreactive IL-1 alpha concentrations in maternal plasma, amniotic fluid and conditioned media from human amniotic fluid and conditioned media from human amniotic, choriodecidual and placental explants were quantified before and after spontaneous term labour-onset and delivery. Furthermore, the effects of a bacterial endotoxin, lipopolysaccharide (LPS), on the release of IL-1 alpha from human gestational tissue explants over a time course of 24 h (n = 3) and LPS concentrations ranging from 10-10(7) pg/ml (n = 3) were investigated. IL-1 alpha concentrations in maternal plasma and amniotic fluid did not change significantly with spontaneous term labour-onset. In contrast, IL-1 alpha was released in detectable amounts from human amniotic and choriodecidual explants only in association with term labour-onset and delivery. Similarly, placental release of IL-1 alpha was increased significantly in explant cultures in association with term labour-onset and delivery. LPS increased IL-1 alpha release significantly only from human placental explants from both term not-in-labour and term after-labour tissues. The data demonstrate differential regulation of IL-1 alpha release from human gestational tissues in association with labour and LPS treatment and the observations support the hypothesis that the labour-associated increase in IL-1 alpha release from the fetal membranes is independent of exposure to bacterial endotoxin.

Differential release of interleukin-6 from human gestational tissues in association with labour and in vitro endotoxin treatment

In this study, we quantified interleukin-6 (IL-6) concentrations in amniotic fluid at term and preterm labour, and determined the gestational tissue source of IL-6. In addition, aspects of the regulatory mechanisms involved in IL-6 release at the time of term labour and in response to bacterial endotoxin, lipopolysaccharide (LPS), have been established. IL-6 concentrations were 2-fold higher in amniotic fluid collected at term compared with preterm gestation, with an additional 2-fold increase in association with term labour. IL-6 was released from all choriodecidual and placental explants but was detected in only 33% of amniotic explant cultures of tissues obtained before labour onset. In contrast, IL-6 was detected in all amniotic, choriodecidual and placental cultures of tissues obtained after term labour onset and delivery, and the mean IL-6 release was significantly higher than that measured in explant cultures of both amniotic (80-fold increase, P < 0.0001) and choriodecidual (3-fold increase, P < 0.02) but not placental explants taken at the time of elective Caesarean section at term before labour onset. LPS significantly (P < 0.05) increased the release of IL-6 from human choriodecidual and placental explants but not amniotic explants, in a time- and dose-dependent manner. IL-6 is a physiological constituent of amniotic fluid and its production by gestational tissues is differentially regulated by LPS and spontaneous labour onset and delivery.

Cellular localization and steroid hormone regulation of mRNA encoding tumour necrosis factor receptor I in mouse uterus

Signals transduced by binding of tumour necrosis factor alpha (TNF) and lymphotoxin alpha (LT-alpha) trimers to high-affinity cell membrane receptors, TNF-RI (p55/p60) and TNF-RII (p75/p80), affect many cell functions. In this study, expression of the gene encoding TNF-RI in uteri of cyclic mice was mapped using in situ hybridization. TNF-RI hybridization signals fluctuated during the cycle. Signal intensity was highest during dioestrus-II, when mRNA encoding TNF-RI was present in endometrial epithelial and stroma cells, as well as in myometrial smooth muscle and connective tissue cells. The ability of oestradiol and progesterone to modulate steady state concentrations of mRNA encoding TNF-RI in uterine cells was assessed by using in situ and northern blot hybridization procedures. Seven days after ovariectomy, low concentrations of mRNA encoding TNF-RI were detected by northern analysis and weak in situ hybridization signals were identified in epithelia and some myometrial connective tissue cells. Administration of oestradiol, progesterone or oestradiol plus progesterone to ovariectomized animals stimulated temporal and cell type-specific changes in steady state concentrations of mRNA encoding TNF-RI that were unique to each hormonal regimen. Maximal induction of mRNA encoding TNF-RI required 24 h of oestradiol stimulation and 72 h of progesterone stimulation. In uteri treated with oestradiol plus progesterone, the oestradiol pattern predominated over the progesterone pattern. Thus, multiple cell types in cyclic mouse uteri express the gene encoding TNF-RI, and expression in specific cells is controlled by female steroid hormones.

Expression and localization of messenger RNA for tumor necrosis factor receptor (TNF-R) I and TNF-RII in pregnant mouse uterus and placenta

The temporal and cell-specific localization of tumor necrosis factor (TNF) receptor mRNAs in the uterus and placenta during pregnancy in the mouse was investigated. Messenger RNA for TNF and the TNF receptors (TNF-RI, p55/p60 and TNF-RII, p75/p80) was assessed by northern blot andin situ hybridization. TNF, TNF-RI and TNF-RII specific transcripts were present on days 7 through 18 of pregnancy. Relative concentrations of TNF mRNA decreased from days 7 to 18 with levels being higher in the uterus than the placenta. In contrast TNF-RI mRNA levels were constant throughout gestation and no differences were seen between steady state levels in the uterus and placenta. Two transcripts for TNF-RII (3.6 and 4.5 kb) were identified in all tissues. Steady state levels of TNF-RII mRNA increased throughout gestation and levels were higher in the placenta than in the uterus. On day 9 of gestation, TNF-RI and TNF-RII mRNAs were localized to undecidualized endometrium, mesometrial decidual cells, and the developing placenta. In addition, muscle cells contained TNF-RI but not TNF-RII mRNA. By day 15 of gestation, TNF-RI and TNF-RII transcripts were primarily localized to the uterine epithelium and trophoblast giant cells and spongiotrophoblast cells in the placenta. The results of these studies reveal the uterine and placental cell-specific expression of TNF receptor mRNAs during pregnancy in the mouse and provide insight into the cellular targets of TNF action.

Tumour necrosis factor alpha during human pregnancy and labour: maternal plasma and amniotic fluid concentrations and release from intrauterine tissues

The aims of this study were: to quantify immunoreactive tumour necrosis factor alpha (TNF-alpha) concentrations in maternal plasma and amniotic fluid obtained from women during pregnancy and labour, both at term and preterm; and to establish the effects of bacterial endotoxin and cytokines on the in vitro release of TNF-alpha from intrauterine tissues. Maternal plasma TNF-alpha concentrations did not change during pregnancy (457.2 +/- 102.9 ng/l, mean +/- SEM, N = 52) or at the time of labour (543.5 +/- 138.6 ng/l, N = 43). In contrast, amniotic fluid TNF-alpha concentrations increased significantly (p < 0.05) during pregnancy (early pregnancy, EP, 93.0 +/- 24.8 ng/l, N = 7; preterm not-in-labour, PNIL, 186.8 +/- 42.9 ng/l, N = 16; term not-in-labour. TNIL, 499.7 +/- 150.9 ng/l, N = 13) and in association with preterm labour (preterm in-labour, PIL, 958.7 +/- 575.6 ng/l, N = 5 vs PNIL, 186.8 +/- 42.9 ng/l, N = 16). Choriodecidual and placental explants (N = 3) maintained in in vitro culture released TNF-alpha. Furthermore, the release of TNF-alpha was increased significantly (p < 0.05) by bacterial endotoxin (lipopolysaccharide, 10 ng/l-10 mg/l) but was not affected by the following cytokines at the indicated doses: interleukin-1 alpha (0.28 nmol/l), interleukin-6 (12.5 nmol/l), granulocyte colony-stimulating factor (2.5 nmol/l), granulocyte-macrophage colony-stimulating factor (35 nmol/l), macrophage colony-stimulating factor (1.2 nmol/l), leukaemia inhibitory factor (0.45 nmol/l) and transforming growth factor-beta (0.4 nmol/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Leukemia inhibitory factor: association with intraamniotic infection

OBJECTIVE

Our purpose was to investigate whether leukemia inhibitory factor is associated with intraamniotic infection.

STUDY DESIGN

A comparative clinical study of amniotic fluid leukemia inhibitory factor concentrations was performed.

RESULTS

Leukemia inhibitory factor was undetectable (< 1 ng/ml) by radioreceptor assay during normal pregnancy at midtrimester and at term. Among women in labor those with intraamniotic infection had higher leukemia factor concentrations than those without infection before term (p < 0.001) and at term (p < 0.005). The leukemia inhibitory factor concentrations correlated with the amniotic fluid white blood cell counts (r = 0.47) (p < 0.001). In cultured human gestational tissue explants, leukemia inhibitory factor release was significantly enhanced by endotoxin, interleukin-1 alpha, and tumor necrosis factor-alpha however, leukemia inhibitory factor did not enhance the release of prostaglandin E2 by these tissues.

CONCLUSIONS

Amniotic fluid leukemia inhibitory factor concentrations were elevated during intraamniotic infection and gestational tissues released leukemia inhibitory factor in response to bacterial products and inflammatory mediators.

Interleukin 8 concentrations in amniotic fluid and peripheral venous plasma during human pregnancy and parturition

To establish the gestational and labour-associated changes in interleukin 8 (IL-8) release, we have determined the concentration of this cytokine in maternal peripheral plasma and amniotic fluid from 15 weeks of gestation to term and in association with spontaneous-onset labour at term and preterm. No statistically significant changes in peripheral plasma IL-8 concentration were observed during pregnancy or in association with labour onset (mean concentration 56.5 +/- 14.5 ng/l, N = 64). The IL-8 concentrations in amniotic fluid were up to 50-fold greater than those observed in peripheral plasma (p < 0.05) and increased significantly (p < 0.05) during pregnancy. At term, but before the onset of labour, amniotic fluid concentrations of IL-8 averaged 969.2 +/- 553.5 ng/l (N = 12). In association with labour at term, IL-8 concentrations increased to 3895.8 +/- 1414.4 ng/l (N = 6, p < 0.03). The concentration of IL-8 in amniotic fluid obtained from women in preterm labour averaged 1854.7 +/- 1352.6 ng/l (N = 6) but was not statistically different from the concentration of IL-8 in amniotic fluid obtained from gestational aged-matched non-labouring controls. Although the precise role of intrauterine IL-8 at the time of parturition awaits elucidation, these data support the concept that this cytokine may be involved in the biochemical events associated with the onset and/or propagation of normal labour in the human.

Elevated plasma interleukin 6: a biochemical marker of human preterm labour

Maternal peripheral venous plasma interleukin 6 (IL-6) concentrations were determined during human pregnancy and labour at term and preterm. During preterm labour, IL-6 concentrations were significantly elevated (p < 0.02) compared to gestationally matched, non-labouring controls (53.7 +/- 15.7 pg/ml, n = 17, and 15.4 +/- 6.4 pg/ml, n = 23, respectively). IL-6 concentrations did not vary significantly during normal pregnancy and labour at term. These data support a role for IL-6 in the pathogenesis of human preterm labour, are evidence for the contention that preterm labour is mechanistically distinct at a biochemical level from normal labour at term and identify maternal peripheral venous plasma IL-6 as a biochemical marker of this condition.