MIT scientists find gut protein intelectin-2 strengthens mucus and traps pathogens

Researchers at MIT have identified a protein called intelectin-2 that performs two distinct defensive functions in the human gut simultaneously. It reinforces the mucus layer that lines the gastrointestinal tract, and it traps and neutralizes harmful pathogens before they can breach that lining. The study, published on March 16, adds a concrete molecular explanation to something scientists have long observed but poorly understood: why the gut mucus barrier in healthy individuals is significantly more effective at blocking infection than its chemical composition alone would predict.

Intelectin-2 is not a newly discovered protein. It has been present in scientific literature for years, mostly as a footnote in broader surveys of gut-secreted proteins. What the MIT team established is that it has an active, mechanistic role in mucosal defense rather than being a passive structural component. That distinction matters for how researchers approach the treatment of diseases where the mucus barrier fails.

How intelectin-2 works in the gut

The mucus layer lining the gut is not a uniform gel. It has two distinct layers: an inner layer that is largely impenetrable to bacteria, and an outer layer where certain microbes can reside. The inner layer's integrity depends on the physical and chemical properties of the mucins, the large glycoproteins that form its scaffold. What the MIT study found is that intelectin-2 binds to specific sugars on those mucins and cross-links them, creating a denser, more cohesive barrier structure than the mucins alone would form.

The pathogen-trapping function works through a different mechanism. Intelectin-2 recognizes and binds to glycan structures found on the surface of many bacterial pathogens, including certain strains of Salmonella and E. coli. Once bound, it essentially immobilizes those pathogens within the mucus matrix, preventing them from reaching the epithelial cells underneath. The MIT team demonstrated this in both in vitro models and in mouse gut tissue, showing that mice with reduced intelectin-2 expression had measurably higher bacterial penetration of their intestinal lining following pathogen exposure.

Why this matters for inflammatory bowel disease

Inflammatory bowel disease, which includes Crohn's disease and ulcerative colitis, affects approximately 3 million people in the United States according to the Centers for Disease Control and Prevention's most recent prevalence data. One of the consistently observed features of both conditions is a degraded or thinned mucus barrier in affected parts of the gastrointestinal tract. The cause of that degradation has been debated for years, with some research pointing to immune dysregulation and other work focusing on microbial community changes.

The intelectin-2 finding adds a new variable to that picture. If reduced intelectin-2 expression contributes to mucus barrier weakening in IBD patients, then therapies that restore or supplement intelectin-2 levels in affected gut tissue could address the barrier defect directly rather than only suppressing the downstream inflammation it triggers. The MIT researchers found that intelectin-2 expression was measurably lower in gut tissue samples from Crohn's disease patients compared to healthy controls, though the study was careful to note this is an association and not yet an established causal relationship.

The innate immune system connection

Intelectin-2 belongs to a protein family called lectins, which are carbohydrate-binding proteins that play various roles in immune recognition. Most of the research attention in mucosal immunity has focused on the adaptive immune system, particularly the role of IgA antibodies secreted into the gut lumen. The intelectin-2 discovery adds weight to the argument that the innate immune defenses operating at the mucosal surface are more sophisticated than previously appreciated and may be a more accessible therapeutic target than the adaptive immune pathways, which are harder to modulate without broad immunosuppressive effects.

The lead researcher on the study, MIT Department of Biology professor Katharina Ribbeck, whose lab has focused on mucus biology for over a decade, described the intelectin-2 findings as filling in a gap in the understanding of how the gut manages microbial threats before the immune system's cellular responses are required. Ribbeck's lab has previously published on how mucins trap viruses and how hormonal changes affect mucus composition, making this study a continuation of a broader research program rather than an isolated discovery.

Potential therapeutic applications and next steps

The most direct therapeutic application being considered is a recombinant intelectin-2 protein that could be administered orally or rectally to patients with ulcerative colitis, targeting the specific segments of colon where the mucus barrier is most compromised. Recombinant protein therapeutics are already used in other gastrointestinal contexts, including recombinant human lactoferrin products, which creates a regulatory and manufacturing pathway that is relatively well understood.

A second direction involves identifying small molecules that can upregulate the body's own intelectin-2 production. The MIT team found that intelectin-2 expression in gut epithelial cells is responsive to certain microbial signals, which suggests it may be possible to use specific probiotic strains or bacterial metabolites to boost natural production. The researchers are currently working with the Broad Institute to screen existing compound libraries for molecules that increase intelectin-2 gene expression in intestinal organoid models. Results from that screening effort are expected to be published in late 2026.