GutPath captures how infection rewires the ileum at single-cell resolution
The ileum rarely gets the same attention as the colon, yet it sits at a biologic crossroads: nutrient absorption, barrier defense, and frontline sensing of invading microbes all converge there. A new single-cell atlas, GutPath, maps how the distal small intestine responds when that balance is disrupted by organisms spanning viral, bacterial, fungal, protozoan, and helminthic infection models. Built from more than 500,000 cells profiled with RNA and protein readouts, the resource offers a direct view of how the ileal epithelium and its immune neighbors shift across distinct infectious settings.
The dataset is large enough to move beyond broad immune labels. It resolves 91 annotated ileal cell states and 49 mesenteric lymph node states, giving investigators a structured reference for both tissue compartments. In practical terms, that means the atlas does not merely catalog which cells are present; it captures how the same tissue can reprogram itself differently depending on whether the challenge comes from a commensal bacterium, an opportunistic fungus, a protozoan parasite, or a helminth.
One of the clearest messages from the atlas is that epithelial biology in the ileum is not static. Enterocytes, goblet cells, Paneth cells, tuft cells, and other specialized populations are all part of a barrier system that must absorb nutrients while resisting invasion. During infection, those cells do not respond in a uniform way. GutPath shows established immune responses in ways that align with known infection biology, but it also uncovers pathogen-specific epithelial programs, especially in enterocytes, where transcriptional states diverge according to the organism driving the insult.
A 500,000-cell atlas anchored in infection biology
The experimental design deliberately spans distinct infectious archetypes. The study included segmented filamentous bacteria, Yersinia pseudotuberculosis, Nippostrongylus brasiliensis, Candida albicans, Cryptosporidium parvum, and murine norovirus CR6. All organisms were administered orally except for the subcutaneous delivery of Nippostrongylus third-stage larvae, and tissues were collected during the first week of infection for sequencing and infection confirmation. For Nippostrongylus, duodenal samples were also collected because the parasite is largely confined to the proximal small intestine.
The technical depth matters. Across the mesenteric lymph node, epithelial compartment, and lamina propria fractions, mean read depth exceeded 30,000 for mRNA and 8,000 for antibody-derived tags. After quality control, 505,956 cells remained for analysis, split between 184,973 mesenteric lymph node cells and 320,983 ileal cells. Those are not abstract numbers; they are the scale required to detect rare states, transient inflammatory transitions, and tissue-localized programs that would disappear in smaller datasets.
The atlas also captures the anatomy of intestinal immunity as more than a simple epithelial-immune divide. The ileum contains absorptive enterocytes that change function along the villus axis, crypt-based stem cells that generate new absorptive lineages, and lamina propria immune cells that control tolerance and pathogen defense. Stromal cells and enteric neurons add another layer of tissue organization. Infection forces all of those compartments to communicate under stress, and GutPath records that communication at single-cell and protein resolution.
A single infection can produce several biologically distinct programs at once.
Pathogen-specific enterocyte states emerge during bacterial and helminth infection
The most consequential finding is the discovery potential of the atlas itself. GutPath identifies a new enterocyte transcriptional state during Yersinia pseudotuberculosis infection, and spatial data link that state to bacterial burden and tissue pathology. That association is biologically persuasive: bacterial load and epithelial damage are likely to shape local inflammatory cues, nutrient transport demands, and barrier repair programs in adjacent epithelial cells. In a tissue built to absorb bile acids, vitamin B12, water, sodium, and chloride, the cost of switching transcriptional gears is not trivial.
The study also points to infection-specific cell–cell signaling programs during Nippostrongylus brasiliensis and Yersinia pseudotuberculosis infection. Helminth and bacterial challenge do not impose the same pressures on the ileum, and the atlas reflects that difference. A helminthic infection tends to favor coordinated mucosal remodeling and type 2-biased responses, while an invasive bacterium is more likely to drive epithelial damage, inflammatory recruitment, and local containment strategies. GutPath does not reduce those responses to a single immune signature; it reveals the transcriptional diversity behind them.
Because the tissue was analyzed with spatially resolved single-cell transcriptomics, the atlas also shows that these responses are not distributed evenly. Localized, regional, and tissue-wide enterocyte changes all appear during infection, suggesting that the ileum integrates proximity to microbial burden with broader tissue-level inflammatory instruction. For clinicians and translational researchers, that has direct relevance to Crohn’s disease, where ileal inflammation is a defining feature in a substantial subset of patients and where epithelial dysfunction contributes to malabsorption and persistent disease activity.
Why the ileum needed its own infection atlas
Small-intestinal immunology has lagged behind colonic studies for a simple reason: the ileum is harder to sample and historically harder to profile at scale. Yet its physiology is distinct. It is the main site for bile acid and vitamin B12 absorption, and its epithelial barrier must defend against pathogens that use Peyer’s patches as entry points. Infection here can lead to diarrhea, growth failure, and in severe global settings, death. The atlas is therefore not just a technical achievement; it addresses a biologic blind spot in mucosal immunology.
The broader value of GutPath lies in comparison. Earlier intestinal single-cell studies established many baseline cell states and helped define steady-state epithelial zonation, but infection-driven processes were underrepresented. This atlas fills that gap by placing disparate infections into a common framework. It gives investigators a reference for asking which epithelial responses are shared across pathogens, which are unique to a given organism, and which are likely to reflect tissue damage rather than pathogen identity.
GutPath also provides a platform for studying how epithelial and immune compartments coordinate during infection rather than in isolation. The mesenteric lymph node data extend the analysis beyond the tissue of injury, adding a systemic immunologic readout that may help explain how local infection shapes downstream immune activation. For future work, the most useful question may be not whether a pathogen triggers inflammation, but which transcriptional routes the ileum uses to contain that pathogen while preserving absorption and barrier integrity.
What this atlas cannot do yet is establish causality. The new enterocyte state linked to Yersinia pseudotuberculosis infection is compelling, but the mechanistic steps that create and sustain it still need functional testing. The same is true for the signaling circuits observed in helminth and bacterial infection. Even so, the resource supplies a map dense enough to guide those experiments, and in a tissue as heterogeneous as the ileum, that may be the most important advance of all.