It shouldn’t have been there,
but there was no denying
that it was there: a channel
guiding immune cells directly into the
brain. The serendipitous discovery
by a University of Virginia team
may eventually help explain many
neurological diseases.
Previously, researchers assumed
immune cells took an indirect route
around the brain, flowing freely
through its surrounding fluid. That’s
because lymphatic vessels, which
transport immune cells throughout
the body, stopped at the upper neck.
So neuroimmunologist Jonathan
Kipnis and his team weren’t looking
for lymphatic vessels actually
entering the brain. “You don’t look
for something that doesn’t exist,”
Kipnis says.
But when Antoine Louveau, a
researcher in Kipnis’ lab, developed
a dissection technique that wholly
preserves the fragile membranes
covering the mouse brain, it revealed
something never seen before:
Immune cells in the membranes were
clearly organized, as if traveling
within tubes. Staining confirmed
there were tubes and that they were
indeed lymphatic vessels — the first
proof they existed in the brain.
The findings, published in Nature
in July, could unearth the secrets of
neurological diseases and disorders,
like multiple sclerosis and Alzheimer’s,
that may involve the immune system.
“It is very possible that the answer to
this question is within the lymphatic
vessels,” Kipnis says.