Researchers at WashU Medicine discovered lymph node-like structures (cyan) in the skull bone marrow of mice that play a role in mounting a rapid immune response in the brain.
Image Credit: Jang Hyun Park/WashU Medicine
Scientific Frontline: Extended "At a Glance" Summary: Skull Bone Marrow Lymphoid Structures
The Core Concept: Researchers have discovered lymph node-like hubs within the skull's bone marrow that function as rapid-response immune "security stations" directly defending the brain.
Key Distinction/Mechanism: Unlike the historical assumption that the brain is isolated from the immune system, these structures show that the brain communicates with localized immune centers. Proteins travel from the brain through tiny channels into the skull marrow, where T follicular helper cells assist B cells in generating targeted antibodies, bypassing the wait for peripheral lymph nodes to respond.
Major Frameworks/Components:
- Skull Bone Marrow Lymphoid Hubs: Newly identified specialized immune structures acting as training centers for immune cells.
- T Follicular Helper Cells & B Cells: Immune cells collaborating within these hubs to produce antibodies.
- Neuroimmunology Communication Channels: Physical conduits allowing proteins, cells, and waste to move between brain tissue and the skull bone marrow.
Branch of Science: Neuroimmunology, Pathology, and Immunology.
Future Application: The discovery introduces the possibility of delivering targeted therapies (such as immune-boosting proteins via localized scalp gels) directly to these skull hubs to treat brain tumors, Alzheimer's disease, Parkinson's disease, schizophrenia, and long COVID, avoiding the severe side effects of systemic peripheral treatments.
Why It Matters: This fundamentally changes the understanding of neuroimmunology by proving the brain possesses a dedicated, localized immune defense system, offering an entirely new physiological pathway for treating aggressive neurodegenerative diseases and brain cancers like glioblastoma.
Researchers at Washington University School of Medicine in St. Louis have discovered lymph-node-like structures in the skull bone marrow of mice for the first time, demonstrating that they act as rapid first responders against brain cancer before distant lymph nodes receive the signal that abnormal cells are present. The researchers also found evidence of similar immune cells in human skull bone marrow.
For decades, scientists assumed that the brain and the immune system did not communicate. The new study reveals that the brain not only communicates with the immune system but also has positioned immune "security stations" nearby, closer than other organs do.
"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," said senior author Jonathan Kipnis, the Alan A. and Edith L. Wolff Distinguished Professor of Pathology and Immunology and a BJC Investigator at WashU Medicine. "Uncovering this localized immune niche changes how we view neuroimmune interactions and opens exciting new avenues for treating brain tumors and other neurological diseases."
The Brain's Dedicated First Responder
Kipnis's lab challenged the once widely accepted idea that the brain is shielded from the immune system when researchers there discovered lymphatic vessels running through the dura mater, the outer tissue layer enveloping the brain beneath the skull. More recently, his team identified tiny physical channels bridging the skull, dura, and brain tissue, revealing a direct conduit for immune cells and cellular waste to move between the brain and local skull bone marrow.
In the new study in mice, researchers tracked the movement of proteins from the brain through the channels directly into the skull’s bone marrow, where they uncovered immune system structures typically found in lymph nodes. These act as the immune system's training hubs, where T follicular helper cells—a type of immune cell—assist other immune cells, called B cells, in creating large amounts of powerful antibodies that help fight disease and infection.
"We have never seen such structures in healthy bone marrow before," said Jang Hyun Park, the study’s first author and a postdoctoral research fellow in the Kipnis lab, who is starting his own lab at the Korea Advanced Institute of Science and Technology this fall. "It is an exciting discovery that points out that a complex brain requires its own specialized immune structures to defend it."
How Can the Skull's Immune System Combat Cancer?
To test whether these nearby hubs actively protect against brain disease, the team used a model of glioblastoma, an aggressive form of brain cancer. They found that in mice with brain cancer, disrupting the skull immune hubs with a drug caused tumors to grow faster than in mice with intact hubs. Impairing the hubs' function caused a drop in survival rates, demonstrating that the brain actively relies on these local centers for defense against cancer.
The researchers also developed a targeted therapy designed to supercharge antibody production inside the skull marrow. By delivering a mixture of three immune-boosting proteins via a gel applied directly under the scalp, the researchers prompted a wave of tumor-fighting immune responses to attack the cancer. These responses, the study found, occurred first in the immune hubs within the skull bone marrow, and then later in nearby lymph nodes outside the skull. Mice treated with the gel experienced greater tumor rejection and lived longer compared with control mice.
"The finding fundamentally changes our current understanding of neuroimmunology," said Kipnis. "Knowing that the brain relies on first responders in the surrounding skull for defense has the potential to change how we think about developing therapies for many neurological conditions, including Alzheimer's disease, Parkinson's disease, schizophrenia, long COVID, and many others that have an immune component to them. Such therapies could access these immune hubs directly through the skull, without major peripheral side effects."
Funding: This work was supported by grants from the National Institutes of Health, grant number R37AG034113; the Cure Alzheimer's Fund; the BJC Investigators Program at WashU Medicine; the Basic Science Research Program through the National Research Foundation of Korea (NRF) by the Ministry of Education, grant number 2022R1A6A3A03065522; and by a fellowship grant from the ChadTough Defeat DIPG Foundation.
Disclaimer: The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.
Competing interests: Jonathan Kipnis is a co-founder of Pranas Neuro, Rho Bio, and Argo Neurotech.
Published in journal: Nature
Title: Functional role of skull lymphoid structures in CNS immunosurveillance
Authors: Jang Hyun Park, Daviti Abramishvili, Gustavo Gastão Davanzo, Ruben Silva, Xingxing Gu, Siling Du, Daniel D. Lee, Bernd H. Zinselmeyer, Jackson S. Turner, Gwendalyn J. Randolph, Igor Smirnov, and Jonathan Kipnis
Source/Credit: Washington University School of Medicine in St. Louis | Marta Wegorzewska
Edited by: Scientific Frontline
Reference Number: imgy082126_01
