Cytokine-Mediated Immunopathology at the Maternal-Fetal Interface in Listeria monocytogenes Infection

Background: Pregnancy requires a shift toward a Th2-like immune response for immunotolerance of the semi-allogeneic fetus. While essential, this shift compromises the woman ability to fight intracellular infections, particularly from Listeria monocytogenes. Objectives: This study aimed to investigate the role of key pro-inflammatory cytokines at the maternal-fetal interface in pregnant women infected with L. monocytogenes, and to determine how their levels correlate with adverse obstetrical outcomes. Methodology: A prospective case-control study was conducted from December 2024 to April 2025 at two tertiary care hospitals in Iraq. Placental tissues and cervical swabs specimens from 150 women with spontaneous abortion, intrauterine death, and preterm labor were examined. Samples underwent enrichment culture on PALCAM medium, and final identification by PCR for 16SrRNA. Maternal serum samples were collected from patients and 50 samples adapted from healthy women, and cytokine concentrations were quantified using enzyme-linked immunosorbent assays. Results: L. monocytogenes was detected in 18/150 (12%) specimens, with highest prevalence in spontaneous abortion cases (50%), followed by preterm labor (27.7%) and stillbirth (22.2%). Quantification results of TNF-α (610.6 pg/ml), IL-6 (243.2 pg/ml), and IL-17 (257.2 pg/ml) were found in cases of intrauterine death, while the lowest levels of IFN-γ were found in abortion cases. Elevated levels of IFN-γ were a hallmark of abortion, while moderately increased levels of IL-6 and IL-17 were observed in preterm labor, along with consistently high levels of TNF-α. Elder women (36-40 years old) showed increased cytokine responses, especially IL-6, IL-17, and IFN-γ, according to age-stratified data, which suggests that inflammatory responses are amplified with age. Conclusion: This study concluded that Listeria monocytogenes infection during pregnancy is strongly associated with elevated pro-inflammatory cytokines, which contribute to adverse obstetrical outcomes such as intrauterine death, abortion, and preterm delivery.