[Two individuals under the same skin--immune mechanisms in pregnancy]

The fetus may be regarded as an allograft in the maternal organism. This paper gives an overview of pregnancy-associated immune mechanisms, based on the literature and studies performed by the authors. During implantation, maternal tissues are invaded by fetal trophoblasts expressing HLA-G, a trophoblast-specific variant of HLA Class I antigens. Recognition of HLA-G stimulates uterine natural killer cells to cytokine production, by which an intrauterine immunosuppression is established. Development, growth and differentiation of placenta is regulated by the cytokines produced. Uterine leukocyte population and expression of cytokine receptors in placental tissues varies throughout gestation, and the complex interplay between trophoblasts and uterine cells, involving a number of cytokines, cytokine receptors, adhesion molecules, enzymes and hormones, changes with gestation. Some cytokines, such as tumour necrosis factor and interleukin-1, may threathen the reproductive process and fetal well-being in high doses. A tight regulation of cytokine activities is probably obtained by the observed upregulation of endogenous cytokine buffer mechanisms in pregnancy. The reproductive success and phenomenons like implantation, placental growth and development, maintenance of pregnancy and delivery, appear to rely on complex, gestational age related interplay between cells of fetal origin and the maternal immune system.

LPS mediated production of IL-1, PGE2 and PGF2alpha from term decidua involves tumour necrosis factor and tumour necrosis factor receptor p55

Prostaglandins, with cytokines involved as intermediate factors, may have an essential role in premature labour when infection is present. We therefore wanted to study tumour necrosis factor (TNF), in cytokine and prostaglandin production in reproductive tissue. Decidual cell cultures were established and cells were stimulated with lipopolysaccharides (LPS). Media concentrations of TNF, interleukin-1 (IL-1), IL-6 and prostaglandin E2 and F2alpha were analysed, and involvement of LPS receptor CD14, TNF and TNF receptors (p55 and p75) were analysed, by studying effects after administration of specific antibodies. LPS induced an early peak elevation of TNF, with a subsequent release of IL-1, IL-6 and prostaglandins. Antibodies against CD14 inhibited these LPS effects. TNF antibodies reduced production of IL-1 and prostaglandins, whereas no significant influence on IL-6 production was observed. Antibodies against the TNF receptor p55 reduced all observed TNF effects. In contrast, p75 antibodies did not influence cytokine or prostaglandin production in this system. Our results suggest that increased TNF production is a prerequisite for LPS stimulated production of IL-1 and prostaglandins from decidual cells. LPS may directly stimulate IL-6 production. Of the two TNF receptors studied, only p55 seemed to be involved in the TNF signal transduction.

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.

Reduced production of PGE2 and PGF2 alpha from decidual cell cultures supplemented with N-3 polyunsaturated fatty acids

A diet rich in n-3 polyunsaturated fatty acid (PUFA) may reduce the intrauterine production of prostaglandins and prolong pregnancy. We tested this hypothesis by assessing the influence of various PUFAs on the spontaneous production of PGE2 and PGF2 alpha from decidual cell cultures. In addition, we assessed prostaglandin and cytokine production stimulated by lipopolysaccharides (LPS) in order to mimic parturition where infection is involved. In both settings, we found that after supplementing with n-3 PUFA, PGE2 and PGF2 alpha were significantly reduced. After supplementing with n-6 PUFA, there was a significant increase in both prostaglandins. Both n-3 and n-6 PUFAs reduced the production of interleukin 1 (IL-1), while n-6 PUFAs reduced TNF production. PUFAs did not influence IL-6 production. Our findings support the hypothesis that dietary n-3 PUFA may prolong pregnancy by reducing intrauterine production of prostaglandins.

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.

Interleukin-6 concentrations in neonates evaluated for sepsis

OBJECTIVES

This study was performed to determine serum concentrations of interleukin-6 (IL-6) during bacterial infections in the first week of life and to evaluate the usefulness of IL-6 as a diagnostic test for perinatal bacterial infections, alone and in combination with C-reactive protein (CRP).

STUDY DESIGN

Blood was obtained from 241 newborn children on admission to the neonatal intensive care unit and at 3 to 4 days after admission. Both samples were analyzed for IL-6, CRP, and white blood cell count with differential.

RESULTS

Twenty-four newborns were classified as having an infection. Increased serum IL-6 levels were detected in infected compared with noninfected newborns on admission (p < 0.0001). Detection of IL-6 (> or = 20 pg/ml) alone yielded a sensitivity of 78%, a specificity of 71%, a positive predictive value of 40%, and a negative predictive value of 93%. A combined parameter of IL-6 (> or = 50 pg/ml) and CRP (> or = 10 mg/L) yielded a sensitivity of 96%, a specificity of 74%, a positive predictive value of 49%, and a negative predictive value of 99%.

CONCLUSIONS

Used in combination with CRP, IL-6 seems to be a valuable parameter in the early diagnosis of neonatal infections.

Infections in neonates delivered at term are associated with increased serum levels of ICAM-1 and E-selectin

All newborn infants consecutively admitted to the Neonatal Intensive Care Unit (NICU) at the University Hospital of Trondheim during 1993 were eligible to participate in the study. In total, 241 neonates were included, for whom anamnestic, clinical and laboratory characteristics were recorded. Peripheral blood was retrieved at admittance, and serum levels of soluble intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin were determined. Newborn infants were classified as infected or non-infected according to selected criteria, and 24 newborn infants fulfilled the criteria of having an infection, whereas 168 newborn infants were classified as non-infected. ICAM-1, VCAM-1 and E-selectin were detected in all neonatal samples. Serum concentrations of E-selectin varied by gestational age (GA), higher levels were found in non-infected term (GA > or = 37 weeks) neonates (n = 53) than in those (n = 115) delivered prematurely (GA < 37 weeks) without infection (p < 0.0001), whereas ICAM-1 and VCAM-1 concentrations did not differ between groups of non-infected term and preterm newborn infants. Similarly, newborn infants delivered at term (n = 16) demonstrated higher levels of E-selectin than premature infants (n = 8) in association with infection (p < 0.001). Both ICAM-1 and E-selectin were increased in term newborn infants with infection (n = 16) compared to the non-infected term group (n = 53) (both p < 0.01), whereas VCAM-1 concentrations did not differ between the two groups. In the premature groups of infected (n = 8) and non-infected (n = 115) neonates, no differences in ICAM-1, VCAM-1 and E-selectin concentrations were observed. The use of ICAM-1 concentration (cut-off level: 250 micrograms l-1) as a diagnostic test for infection in term neonates yielded a sensitivity of 80% and a specificity of 61%, whereas a sensitivity of 70% and a specificity of 79% were found when E-selectin concentration (cut-off level: 150 micrograms l-1) was used. Conclusively, increased shedding of soluble ICAM-1 and E-selectin is one component of infection-induced neonatal immune response after full-time pregnancies. Our data suggest that the ability of increased shedding of soluble ICAM-1 and E-selectin molecules is developed during the final weeks of pregnancy. Assessment of ICAM-1 and E-selectin concentrations may be used as diagnostic tools with a high sensitivity and a moderate specificity in term neonates suspected of infection.

Maternal serum levels of interleukin-6 and clinical characteristics of normal delivery at term

BACKGROUND

The objective of the present study was to study participation of cytokines and cytokine inhibitors during the process of normal parturition, as assessed by maternal serum levels of interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor (TNF) and soluble tumor necrosis factor receptors (sTNFRs, p55 and p75).

MATERIALS AND METHODS

Twenty-six healthy women in normal term labor were observed during parturition and until 2 h post partum. Serum was sampled every 2 h, and an evaluation of strength and frequency of contractions was performed at the time of sampling. Concentrations of IL-1, IL-6, TNF, p55 and p75 were analyzed, and non-parametric tests were used to study whether any relationship existed between the serum analyzes and the clinical characteristics of parturition.

RESULTS

There was a significant association between the strength of contractions and the levels of IL-6 and p55. In addition, IL-6 concentrations and frequency of contractions were correlated. Maternal serum levels of IL-6 and p55 were highest 2 h post partum. TNF activity was detected in samples from nine women, whereas IL-1 was not found in any sample.

CONCLUSIONS

The present study suggests a role of IL-6 and p55 in normal labor. However, as women being studied already were in labor, the study does not allow any conclusions whether observed changes in IL-6 and p55 levels have a causal relation to the process of labor or if changes are secondary effects of the process itself.

Chromogranin A and pancreastatin-like immunoreactivity in normal pregnancies

Placenta is a neuroendocrine organ, and we therefore wanted to study the occurrence of the general neuroendocrine marker chromogranin A (CgA) and its split product pancreastatin. CgA and pancreastatin-like immunoreactivity (PST-LI) were determined by ELISA and RIA methods, respectively, in homogenates from term placentas, sera from pregnant women, nonpregnant women, umbilical cords, and in amniotic fluids. In placental homogenates, the mean level of CgA was 7.1 +/- 8.6 pmol/g wet wt (mean +/- SD), whereas PST-LI was not detectable. CgA immunoreactivity was demonstrated by immunofluorescence studies of isolated trophoblasts and decidual cells from term placentas. In trophoblasts, CgA was colocalized with human chorionic gonadotropin (hCG) and human placental lactogen. By Northern blotting, a distinct band corresponding to CgA messenger RNA (mRNA) was demonstrated in the placental cell line, whereas, in placental homogenates, a mRNA band of a slightly larger size was found. Median CgA level in maternal sera at term tended to be higher (median: 469 pmol/L, range 61-980 pmol/L, P < 0.1) than at 6-11 weeks (286 pmol/L, 61-653 pmol/L) or in sera from nonpregnant women (306 pmol/L, 204-469 pmol/L). In umbilical cord sera, median CgA level was significantly higher (898 pmol/L, 102-2245 pmol/L, P < 0.05) than in term sera. Median serum level of PST-LI was significantly higher at term (38 pmol/L, 0-131 pmol/L) than at 6-11 weeks (9 pmol/L (0-85 pmol/L, P < 0.05), than in nonpregnant women (6 pmol/L, 0-52 pmol/L, P < 0.05), and in umbilical cord sera (12 pmol/L, 0-76 pmol/L, P < 0.05). In amniotic fluid, median CgA value was significantly higher at term (1163 pmol/L, 714-1673 pmol/L) than at 14-17 weeks (551 pmol/L, 82-980 pmol/L, P < 0.01), whereas median level of PST-LI was significantly higher at 14-17 weeks (32 pmol/L, 6-97 pmol/L) than at term (0 pmol/L, 0-15 pmol/L, P < 0.01). To our knowledge, this is the first report describing the presence of CgA and PST-LI in placenta and amniotic fluid and the occurrence CgA mRNA in placental tissue and in a placental cell line. The presence of CgA in placenta may indicate a physiological role in pregnancy.

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.

Detection of cytokines (interleukin-1, interleukin-6, transforming growth factor-beta) and soluble tumour necrosis factor receptors in embryo culture fluids during in-vitro fertilization

Several lines of evidence suggest that a number of immunoactive cytokines participate in early reproductive events such as implantation and placental development. Furthermore, cytokines may influence embryo growth and differentiation. In the present study, the production of tumour necrosis factor (TNF), interleukin-1 (IL1), interleukin-6 (IL6) and transforming growth factor-beta (TGF beta) during the first 48 h after oocyte retrieval during in-vitro fertilization was investigated. In addition, the question was raised whether soluble receptors may contribute to cytokine activity regulation in early reproduction, and concentrations of TNF and IL6 receptors in culture media were determined. Finally, an investigation of whether any association exists between cytokine concentrations and embryo morphology was performed. Media from 256 embryos were analysed. IL1, IL6 and TGF beta were produced during the 48 h culture period, whereas no TNF was detected. Levels of IL1 and IL6 were significantly higher in media from the first 24 h culture period than from the second period, whereas TGF beta concentrations in supernatants from the two observation periods did not differ. IL6 receptors were not detected, whereas TNF receptors (p75) appeared in media from the 24-48 h culture period. Granulosa, cumulus and sperm cells are potential sources of cytokine production, especially during the first 24 h period. The contribution of the embryo to cytokine/cytokine receptor production remains an open question. No significant correlation was observed between cytokine/cytokine receptor concentrations and embryo morphological score.

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.