Inflammatory NF-κB Signaling Comes Alive in the Septa of Newborns with Intestinal Atresia

A blocked or narrowed intestine is one of the most urgent surgical emergencies a newborn can face. In type I intestinal atresia, a thin membrane or septum—little more than a delicate web of tissue—spans the interior of the bowel and obstructs the passage of milk and digestive fluids. Babies born with the condition typically present with abdominal distension and bilious vomiting within hours or days of delivery, and surgeons must remove the obstructing septum and reconnect the healthy ends of the intestine. Yet for all its clinical urgency, the biological events that cause this membrane to form in the first place have remained stubbornly obscure.

Now a team of researchers in Beijing has provided a tantalizing new clue. In a study published in Frontiers in Pediatrics, investigators led by Xuelai Liu of the Capital Center for Children’s Health at Capital Medical University examined human septal tissue removed from eight infants with type I intestinal atresia and found striking evidence that a master inflammatory circuit—the nuclear factor kappa B, or NF-κB, signaling pathway—is switched on inside the very tissue that blocks the bowel. Because the fetal intestine develops in an essentially sterile environment, the finding points toward an internally driven immune dysregulation during embryonic development, rather than a response to external infection.

The NF-κB pathway is one of the most heavily studied signaling cascades in immunology. Under resting conditions, a protein complex consisting of p65 bound to p50 sits inertly in the cytoplasm, tethered by an inhibitory partner called IκB-α. When inflammatory stimuli arrive, a kinase called IKK-β phosphorylates the inhibitor, freeing the p65/p50 heterodimer to enter the nucleus and switch on target genes. Upstream of this event, transforming growth factor-β-activated kinase 1, or TAK1, feeds signals into the IKK complex. Once activated, the pathway drives the production of powerful pro-inflammatory messengers such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6).

To determine whether this cascade behaves abnormally in atresia, the team collected septa and adjacent proximal intestinal wall tissue from eight patients operated on at Beijing Children’s Hospital Heilongjiang Hospital between September 2016 and December 2021. All eight infants had prenatal imaging showing dilated small bowel and were confirmed intraoperatively and pathologically to have type I atresia. Critically, the researchers used each patient’s own nearby normal intestinal wall as an internal control, minimizing the confounding effects of individual biological variation. Tissue was excised with surgical scissors rather than electrocautery to avoid thermal artifacts that could distort protein detection.

The team then applied immunohistochemistry, a technique that uses antibodies to visualize specific proteins under the microscope. Five-micrometer sections were incubated with antibodies against TAK1, IKK-α/β, p65 NF-κB, TNF-α, and IL-6, and the bound antibodies were revealed with a brown chromogen. In the normal control tissue, TAK1, IKK-α/β, and p65 NF-κB showed only weak staining in the cytoplasm of the glandular epithelial cells lining the mucosal glands. In the septal mucosa, however, all three proteins were dramatically more abundant, painting the glandular epithelium with dense brown-yellow reactivity.

Semiquantitative analysis backed up what the microscopes showed. Using Image-Pro Plus software, the researchers measured mean optical density across randomly selected fields in a double-blind assessment. The optical density of TAK1 rose from 0.040 ± 0.005 in normal wall to 0.265 ± 0.030 in septum, a more than sixfold increase with a p-value of 0.0008. IKK-α/β climbed from 0.075 ± 0.010 to 0.340 ± 0.040 (p = 0.0006), and p65 NF-κB rose from 0.035 ± 0.005 to 0.270 ± 0.030 (p = 0.0008). Together, these measurements indicated that the entire core of the NF-κB cascade—from its upstream kinase to its nuclear effector—is upregulated in septal tissue.

Activation of the pathway should, in principle, translate into increased production of its downstream inflammatory products, and that is precisely what the team observed. TNF-α staining in the mucosa rose from an optical density of 0.025 ± 0.005 in normal wall to 0.072 ± 0.004 in septum (p = 0.0003), while IL-6 increased from 0.042 ± 0.005 to 0.055 ± 0.004 (p = 0.0165). Even the muscular layer showed the signature: TNF-α rose from 0.013 ± 0.004 to 0.034 ± 0.007 and IL-6 from 0.004 ± 0.001 to 0.046 ± 0.007. The cytokine data, the authors argue, confirm that the pathway is not merely present but functionally ignited within the septum.

The developmental context makes the finding particularly provocative. During gestation, the fetal gut is normally free of bacteria, shielded by the antimicrobial properties of amniotic fluid and the protective placental barrier. It is only after birth that microbes colonize the infant’s digestive tract and begin educating the immune system. This means the intestinal villi and glands recanalize in a relatively sterile setting, so any inflammatory activity detected in septal tissue likely reflects intrinsic immune dysregulation within the developing bowel rather than a response to microbial invasion. Building on their earlier work showing that gut lumen formation proceeds through vacuoles that merge with the developing mucosal epithelium, the researchers had previously proposed that residual vacuoles might underlie septum formation—and that a reduction in immune barrier-associated cells within septal mucosa could be part of the story.

The authors are careful to acknowledge the limits of their evidence. All specimens were obtained during postnatal surgery, so the detected signals may not exclusively mirror embryonic events; postnatal inflammation and surgical handling could contribute, although the use of adjacent normal tissue from the same patient helps control for these factors. The sample size of eight patients is small, constrained by the rarity of the condition and the inherent difficulty of collecting septal specimens. NF-κB, moreover, is only one node in a vast inflammatory network, and it remains unknown which upstream pathways drive its activation here, whether multiple cascades converge on it, or how inflammatory signaling intersects with the developmental programs that sculpt the embryonic gut.

Even so, the study delivers the first direct histological evidence in human tissue that inflammatory signaling is abnormally engaged in the septa of type I intestinal atresia. By linking a well-characterized inflammatory pathway to a congenital malformation whose cause has eluded explanation, the work opens a concrete molecular avenue for future investigation—one that could eventually reshape how clinicians and scientists understand, and perhaps one day prevent, this obstructing membrane that stands between newborns and a functioning gut.

Subject of Research: NF-κB signaling pathway expression in the septal tissue of type I intestinal atresia

Article Title: Immunohistochemical expression of NF-κB signaling pathway components in the septum of type I intestinal atresia

Article References: Liu, X., Wang, H., Chen, Y., Ye, M., Cui, X., Wei, Y., & He, F. (2026). Immunohistochemical expression of NF-κB signaling pathway components in the septum of type I intestinal atresia. Frontiers in Pediatrics, 14, Article 1978002. https://doi.org/10.3389/fped.2026.1978002

Image Credits: AI Generated

DOI: 10.3389/fped.2026.1978002

Keywords: intestinal atresia, NF-κB, septum, TAK1, IKK, p65, TNF-alpha, IL-6, inflammation, embryonic development, pediatric surgery, immunohistochemistry