Cellular immune responses in amniotic fluid of women with preterm labor and intra‐amniotic infection or intra‐amniotic inflammation

Abstract

Problem: Preterm birth is commonly preceded by preterm labor, a syndrome that is causally linked to both intra-amniotic infection and intra-amniotic inflammation.However, the stereotypical cellular immune responses in these two clinical conditions are poorly understood.Method of study: Amniotic fluid samples (n = 26) were collected from women diagnosed with preterm labor and intra-amniotic infection (amniotic fluid IL-6 concentrations ≥2.6 ng/mL and culturable microorganisms, n = 10) or intra-amniotic inflammation (amniotic fluid IL-6 concentrations ≥2.6 ng/mL without culturable microorganisms, n = 16). Flow cytometry was performed to evaluate the phenotype and number of amniotic fluid leukocytes. Amniotic fluid concentrations of classical proinflammatory cytokines, type 1 and type 2 cytokines, and T-cell chemokines were determined using immunoassays.Results: Women with spontaneous preterm labor and intra-amniotic infection had (a) a greater number of total leukocytes, including neutrophils and monocytes/macrophages, in amniotic fluid; (b) a higher number of total T cells and CD4 + T cells, but not CD8 + T cells or B cells, in amniotic fluid; and (c) increased amniotic fluid concentrations of IL-6, IL-1β, and IL-10, compared to those with intra-amniotic inflammation. However, no differences in amniotic fluid concentrations of T-cell cytokines and chemokines were observed between these two clinical conditions. K E Y W O R D S chorioamnionitis, fetal inflammatory response syndrome, funisitis, microbial invasion of the amniotic cavity, placental inflammation, pregnancy | 3 of 15 GOMEZ-LOPEZ et al. | Placental histopathological examinationPlacentas were examined histologically by perinatal pathologists blinded to clinical diagnoses and obstetrical outcomes according to standardized Perinatology Research Branch protocols. 75,76 Briefly, three to nine sections of the placenta were examined, and at least one full-thickness section was taken from the center of the placenta; others were taken randomly from the placental disk. Acute inflammatory lesions of the placenta (maternal inflammatory response and fetal inflammatory response) were diagnosed according to established criteria, including staging and grading. 75,77 The proportions of patients whose placentas presented acute maternal and/or fetal inflammatory responses are displayed in Table 1. | Amniotic fluid sample collectionAmniotic fluid samples were obtained by transabdominal amniocentesis under antiseptic conditions and monitored by ultrasound in order to detect intra-amniotic inflammation and/or infection in patients with preterm labor. Samples of amniotic fluid were transported to the laboratory in a sterile, capped syringe and immunophenotyping was performed immediately. The rest of the sample was centrifuged at 1300 g for 10 minutes at 4°C, and the supernatant was stored at −80°C until use. Also, an aliquot of amniotic fluid was transported to the clinical laboratory for culture of aerobic/anaerobic bacteria and genital mycoplasmas. The clinical tests also inc...

Cellular immune responses in amniotic fluid of women with preterm prelabor rupture of membranes

“…Studies investigating the functions of amniotic fluid neutrophils have shown that these innate immune cells can phagocytize bacteria invading the amniotic cavity [67], form neutrophil extracellular traps (NETs) [68], and may degranulate, releasing anti-microbial molecules such as myeloperoxidase [69][70][71], alpha-defensins [70,[72][73][74], elastase [70,75,76], cathepsin G [70,77], lactoferrin [78], pentraxin-3 [79], and cathelicidin [69,70] as well as reactive oxygen species [80] into the amniotic cavity. In addition to participating in the host defense response to microbes, neutrophils can also release pro-inflammatory cytokines such as IL-8, tumor necrosis factor-α (TNF-α), macrophage inflammatory protein-1α (MIP-1α), MIP-1β, IL-1α, and IL-1β, which are implicated in the mechanisms leading to premature labor in the context of intra-amniotic infection [52,53,[81][82][83][84][85][86][87][88][89][90][91][92][93][94]. Furthermore, amniotic fluid neutrophils may also participate in the pathogenesis of pPROM by releasing neutrophil elastase and metalloproteinases [76,[95][96][97][98]…”

“…Specifically, neutrophils, monocytes/macrophages, T cells, innate lymphoid cells, natural killer (NK) cells, and B cells are present in the amniotic cavity of women with a normal pregnancy [49][50][51]. These cellular immune responses are augmented in women with pregnancy complications such as preterm labor with intact membranes [52], clinical chorioamnionitis at term [53], and preterm clinical chorioamnionitis [54]. However, the cellular immune responses in amniotic fluid of women with pPROM have not been investigated.…”

Maternal and Fetal CD4+CD25+CD127low/- Regulatory T Cells in Pregnancies with Gestational Diabetes, Preeclampsia, and Premature Rupture of Membranes

“…It is generally believed that preterm PROM is causally linked to intra-amniotic inflammation and intra-amniotic infection [18]. Studies have shown that women with intra-amniotic infection had a higher number of total T and CD4 + T cells in amniotic fluid [19]. There are phenotypic changes in granulocytes and Tregs, which are consistent with the presence of intravascular inflammation in preterm PROM and preterm labor patients [20,21].…”

Microbial burden and inflammasome activation in amniotic fluid of patients with preterm prelabor rupture of membranes

“…Indeed, in vitro studies have shown that incubation of the chorioamniotic membranes with microbial products such as lipopolysaccharide (LPS) triggers the activation of such a pathway [214]. Another potential cellular source of IL-6 in amniotic fluid is the immune cells present in this compartment, particularly monocytes/ macrophages [215][216][217][218]. Nonetheless, further research is needed to investigate whether viable yet non-culturable microorganisms are sensed by different pattern recognition receptors than culturable microorganisms, leading to distinct inflammatory responses.…”

“…enhanced inflammasome assembly) [81]. Second, amniotic fluid of women with intra-amniotic infection contains large numbers of immune cells such as neutrophils and monocytes/macrophages [215][216][217], which may undergo inflammasome-mediated inflammatory cell death (i.e. pyroptosis) [224].…”