Amniotic fluid IL-6 in preterm labor: association with infection

Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, Connecticut 06510.
Journal of Clinical Investigation (Impact Factor: 13.22). 06/1990; 85(5):1392-400. DOI: 10.1172/JCI114583
Source: PubMed


To evaluate whether IL-6 participates in the host response to intrauterine infection, we studied IL-6 bioactivity and isoforms in amniotic fluid (AF). Two different assays for IL-6 were used: the hepatocyte stimulating factor assay (in Hep3B2 cells) and the SDS-PAGE/immunoblot assay. IL-6 determinations were performed in 205 AF samples. Samples were obtained from patients in the midtrimester of pregnancy (n = 25), at term with no labor (n = 31), at term in active labor (n = 40), and from patients in preterm labor (n = 109). Higher AF IL-6 levels were observed in women in preterm labor with intraamniotic infection than in women in preterm labor without intraamniotic infection (median = 375 ng/ml, range = 30-5000 ng/ml vs. median = 1.5 ng/ml, range = 0-500, respectively, P < 0.0001). The 23-25- and 28-30-kD IL-6 species could be readily detected in SDS-PAGE immunoblots performed directly on 10-μl aliquots of AF from patients with intraamniotic infection. Among women in preterm labor with culture-negative AF, those who failed to respond to subsequent tocolytic treatment had higher AF IL-6 concentrations than those who responded to therapy (median = 50 ng/ml vs. median = 1.2 ng/ml, respectively, P < 0.05). Only low levels of IL-6 were detected in AF obtained from normal women in the midtrimester and third trimester of pregnancy. Decidual tissue explants obtained from the placentas of women undergoing elective cesarean section at term without labor (n = 11) produced IL-6 in response to bacterial endotoxin. In a pilot study, AF IL-6 was determined in 56 consecutive women admitted with preterm labor. All patients (n = 10) with elevated AF IL-6 (cutoff = 46 ng/ml) delivered a premature neonate. 4 of these 10 patients had positive AF cultures for microorganisms. These studies implicate IL-6 in the host response to intrauterine infection and suggest that evaluation of AF IL-6 levels may have diagnostic and prognostic value in the management of women in preterm labor.

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Available from: Pravin Sehgal, Oct 09, 2014
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    • "While available evidence suggests that healthy pregnancy is typified by an enhanced inflammatory state, studies also show that excessive inflammation is incompatible with healthy pregnancy. Elevations in proinflammatory cytokines in maternal serum and amniotic fluid are causally implicated in risk of preterm delivery in the context of infection as well as idiopathic cases [10] [11] [12] [13] [14]. Proinflammatory cytokines can promote preterm labor by triggering preterm contractions, encouraging cervical ripening, and causing rupture of the membranes [15] [16]. "
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    ABSTRACT: Background: The maternal immune system undergoes substantial changes to support healthy pregnancy. Although obesity is a primary driver of inflammation and predictive of perinatal complications, additive effects of pregnancy and obesity on changes in inflammatory processes are not well delineated. Methods: This study examined serum proinflammatory markers interleukin(IL)-6, IL-8, tumor necrosis factor (TNF)-α, IL-1β, and C-reactive protein (CRP) during each trimester of pregnancy and 4-6 weeks postpartum among 57 women. Results: Overall, IL-6 showed an increasing trend across pregnancy and significant increase at postpartum. Similarly, TNF-α increased significantly across gestation, with a further increase at postpartum. Both IL-8 and IL-1β showed a U-shaped curve, decreasing from early to later pregnancy, and increasing at postpartum. Finally, serum CRP decreased significantly across pregnancy, with further decreases at postpartum. Maternal obesity predicted higher IL-6 at each study visit. Obese women showed a trend toward elevated serum CRP during pregnancy, and significantly higher levels at postpartum. Discussion: The course of pregnancy and postpartum is characterized by significant changes in serum proinflammatory mediators. Obese women show elevations in serum proinflammatory markers relative to normal weight women during pregnancy and postpartum. Further research is needed to determine the extent to which obesity-induced inflammation affects maternal and fetal health.
    Cytokine 07/2014; 70(2). DOI:10.1016/j.cyto.2014.06.018 · 2.66 Impact Factor
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    • "This gene encodes the pro-inflammatory cytokine interleukin-6 (IL-6), which is involved in the regulation of innate immunity. Several studies have shown that PTB is associated with increased concentration of IL-6 in maternal serum, cervicovaginal secretions and amniotic fluid [23-25]. Many IL6 polymorphisms have been assessed for association with preterm birth [26]. "
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    ABSTRACT: Background Because of the role of inflammation in preterm birth (PTB), polymorphisms in and near the interleukin-6 gene (IL6) have been association study targets. Several previous studies have assessed the association between PTB and a single nucleotide polymorphism (SNP), rs1800795, located in the IL6 gene promoter region. Their results have been inconsistent and SNP frequencies have varied strikingly among different populations. We therefore conducted a meta-analysis with subgroup analysis by population strata to: (1) reduce the confounding effect of population structure, (2) increase sample size and statistical power, and (3) elucidate the association between rs1800975 and PTB. Results We reviewed all published papers for PTB phenotype and SNP rs1800795 genotype. Maternal genotype and fetal genotype were analyzed separately and the analyses were stratified by population. The PTB phenotype was defined as gestational age (GA) < 37 weeks, but results from earlier GA were selected when available. All studies were compared by genotype (CC versus CG+GG), based on functional studies. For the maternal genotype analysis, 1,165 PTBs and 3,830 term controls were evaluated. Populations were stratified into women of European descent (for whom the most data were available) and women of heterogeneous origin or admixed populations. All ancestry was self-reported. Women of European descent had a summary odds ratio (OR) of 0.68, (95% confidence interval (CI) 0.51 – 0.91), indicating that the CC genotype is protective against PTB. The result for non-European women was not statistically significant (OR 1.01, 95% CI 0.59 - 1.75). For the fetal genotype analysis, four studies were included; there was no significant association with PTB (OR 0.98, 95% CI 0.72 - 1.33). Sensitivity analysis showed that preterm premature rupture of membrane (PPROM) may be a confounding factor contributing to phenotype heterogeneity. Conclusions IL6 SNP rs1800795 genotype CC is protective against PTB in women of European descent. It is not significant in other heterogeneous or admixed populations, or in fetal genotype analysis. Population structure is an important confounding factor that should be controlled for in studies of PTB.
    BMC Genetics 04/2013; 14(1):30. DOI:10.1186/1471-2156-14-30 · 2.40 Impact Factor
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    • "The findings to date remain inconclusive. The measurement of interleukin 6 (IL-6) in the amniotic fluid (AF) is currently a frequently reported method to diagnose an intrauterine infection [6-8]. Other cytokines, especially IL-8, have also been suggested to have value in the diagnosis of an intrauterine infection [6,9]. "
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    ABSTRACT: Variations in cytokine and immune mediator expression patterns in amniotic fluid due to gestational age, maternal age and fetal gender were investigated. Amniotic fluid samples were obtained from 192 women, 82 with a mid-trimester amniocentesis (median gestational age 17 weeks) and 110 with a caesarean section not in labor (median gestational age 39 weeks). Amniotic fluid was screened by commercial ELISAs for the TH1/TH2/TH17 cytokines and immune mediators IL-1 beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-15, IL-17, TNF alpha, GRO-alpha, MIP1alpha, MIP1beta, Histone, and IP10. Analysis was by Bonferroni correction for multiple comparisons. None of the 15 examined cytokines revealed any differences in expression patterns regarding fetal gender. Significant differences were found in IL-4, IL-10, IL-12, TNF- alpha, GRO-alpha and MIP1-beta with respect to gestational age and in GRO-alpha regarding maternal age. Cytokines utilized as biomarkers in the diagnosis of intrauterine infections are not influenced in their expression pattern by fetal gender but may vary with respect to maternal age and gestational age.
    BMC Research Notes 07/2012; 5(1):375. DOI:10.1186/1756-0500-5-375
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