The skull has traditionally been regarded largely as armor for the brain. New research from the United States suggests it may have another role: proactively helping to defend what lies beneath it. Researchers at Washington University School of Medicine in St.
Louis identified previously unknown immune "security stations" in the bone marrow of mouse skulls. The lymph node-like structures responded to brain tumors before more distant lymph nodes in the neck did. When researchers disrupted the structures in mice with glioblastoma, an aggressive brain cancer, the tumors grew faster and the animals died sooner.
"The skull should no longer be viewed simply as a protective shell around the brain," senior study author Jonathan Kipnis told DW. "It contains specialized immune environments that appear capable of responding locally to changes within the brain." The discovery, published in the journal "Nature," comes with an important caveat: The researchers have so far only demonstrated how the structures function in mice, not humans. Kipnis cautioned that the human evidence remains preliminary: "We found similar immune cells in human skull marrow, suggesting that related structures may exist, but we have not yet demonstrated that they are organized or function in the same way as those in mice," he said.
For much of the 20th century, the brain was described as "immune privileged" — unusually protected from immune activity because inflammation that is useful elsewhere can damage delicate brain tissue. The blood-brain barrier, which tightly controls what can pass from the bloodstream into brain tissue, reinforced the idea that the brain was largely isolated from the body's conventional immune system. Researchers now know that the brain communicates continuously with the immune system, particularly through tissues surrounding the brain.
Kipnis' lab helped drive that rethink in previous work, first by identifying lymphatic vessels in the membranes surrounding the brain and later by showing tiny channels connecting those membranes to the skull's bone marrow. To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video "The traditional concept of immune privilege has already changed substantially," Kipnis said. "Our findings add another layer by showing that specialized immune structures exist within the skull bone marrow, immediately adjacent to the brain." The researchers tracked proteins moving from mouse brains through microscopic skull channels and into the bone marrow.
There they found organized clusters of so-called B cells and T-cells. T cells help B cells in "creating large amounts of powerful antibodies that help fight disease and infection." Finding immune cells in bone marrow was not unusual. The surprise was their organization into structures resembling lymph nodes elsewhere in the body.
Extract — continue reading at the source.
