Scientists find hidden immune organ in skull that fights brain cancer

Researchers at Washington University School of Medicine in St. Louis have identified lymph node-like immune structures inside the skull bone marrow of mice, revealing what they describe as dedicated "security stations" positioned to defend the brain against cancer and potentially other neurological diseases. The study, published August 19 in Nature, marks the first time such immune hubs have been found in bone.medicine.washu+1

A New Frontier in Brain Immunity

For decades, the prevailing scientific view held that the brain and the immune system operated largely in isolation. The new findings upend that assumption, showing the brain not only communicates with the immune system but has stationed immune response centers in the nearest possible location — the skull bone marrow directly above it.medicalxpress+1

The research team, led by senior author Jonathan Kipnis, tracked the movement of proteins from the brain through tiny channels in the skull into the bone marrow, where they discovered structures resembling germinal centers typically found in lymph nodes. In these hubs, T follicular helper cells assist B cells in producing antibodies to fight disease.medicine.washu+1

"This study reveals that the skull bone marrow is far more than just a structural framework — it harbors previously unrecognized hubs for brain-specific immune responses," Kipnis said. First author Jang Hyun Park, a postdoctoral research fellow who is starting his own lab at the Korea Advanced Institute of Science and Technology, called it "an exciting discovery that points out that a complex brain requires its own specialized immune structures to defend it".medicine.washu

Cancer-Fighting Potential

To test the structures' function, the team used a mouse model of glioblastoma. When they disrupted the skull immune hubs with a drug, tumors grew faster and survival declined. Conversely, when they delivered a mixture of three immune-boosting proteins via a gel applied under the scalp, mice experienced stronger tumor-fighting immune responses and lived longer.medicalxpress+1

The researchers also found evidence of similar immune cells in human skull bone marrow, suggesting analogous structures may exist in people. If confirmed, the discovery could open new therapeutic approaches for brain tumors and neurodegenerative conditions including Alzheimer's disease — potentially accessed through the skull without major systemic side effects.medicine.washu+1

Building on a Decade of Discovery

The finding builds on earlier work by the same group, which identified lymphatic vessels in the brain's outer covering and later discovered the tiny channels connecting skull, dura mater, and brain tissue. Eric Topol, a prominent researcher at Scripps Research, noted the discovery's broader implications, writing that the skull's immune role "may also be important vs neurodegenerative diseases such as Alzheimer's".x+2