Researchers at the University of California, Riverside School of Medicine have discovered a previously unrecognized immune surveillance structure in the skin. Found within hair follicles, these cells resemble M (microfold) cells, specialized epithelial cells traditionally associated with tissues of the intestines and respiratory tract.
The survey results are Frontiers of Cell Biology and Developmental Biology, They suggest that the skin may use specialized “sentinel” cells located within hair follicle structures to monitor environmental exposure and the presence of microorganisms, expanding current understanding of how barrier tissues protect the body. This study was conducted in mice.
Senior author Dr. David Roe, Distinguished Professor of Biomedical Sciences, explained that unlike the intestinal and airway epithelia, which are composed of a single cell layer that allows for relatively direct environmental sampling, the skin is composed of multiple stratified layers that form a more robust physical barrier.
This raises a long-standing question in immunology: despite its thickness, how does the skin efficiently monitor external threats?”
Dr. David Roe, Distinguished Professor of Biomedical Sciences
Lo’s team proposes that hair follicles may act as local “gateway” structures that concentrate both environmental substances and immune-sensing activity. Within these niches, the researchers specifically identified M-cell-like sentinel cells that appear to be involved in local immune responses to Gram-positive bacteria, which can cause infections ranging from food poisoning to serious respiratory illnesses.
“Hair follicles may be the central hub of immune surveillance in the skin,” said Diana del Castillo, lead author of the paper and a graduate student in Lo’s lab. “These structures integrate environmental exposure, immune sensing, and potentially even neural signaling in a highly localized environment.”
Although the research team is still characterizing the cells, early findings suggest that these cells are part of a broader category of epithelial surveillance mechanisms that may exist across multiple tissues.
The discovery also raises new questions about how the immune and sensory systems are integrated. Hair follicles are already known to contribute to the sense of touch, and the newly identified structures appear to be located in areas closely associated with nerve endings, suggesting a potential link between immune detection and sensory signaling.
Dr. Low said that because whiskers have dense innervation and complex structures, future studies will focus on detailed anatomical mapping of these cells, particularly the whisker hair follicles in animal models.
“We want to better understand how these cells interact with surrounding nerve and immune cells and whether a similar system exists in humans,” he said.
Although this research is still in its early stages, the findings could have future implications for our understanding of skin infections, immune diseases, and the development of topical treatments.
“We’re just beginning to understand how these systems are organized,” Lo says. “But they suggest that the skin is involved in immune surveillance in a much more dynamic way than previously thought.”
Professor del Castillo said the study highlights a potential shift in the way scientists view barrier tissues not as passive protective layers, but as active, highly specialized sensory and immune interfaces.
“Our study adds to the evidence that epithelial barriers across tissues share more diverse and dynamic immune-related functions than previously appreciated, particularly in their ability to rapidly respond to microbial stimuli,” she said.
Low and del Castillo were also joined in the study by Hannah Kim and Sumaya Troy Arama.
This study was supported by funding from the UCR School of Medicine.
sauce:
University of California, Riverside
Reference magazines:
Del Castillo, D. Others. (2026). Evidence for murine cutaneous immune surveillance localized to the hair follicle epithelium. Frontiers of cell and developmental biology. DOI: 10.3389/fcell.2026.1721181. https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2026.1721181/full
