Wednesday, June 3, 2015

A Brain-Lymphatic Connection

Existing dogma in neuroscience states that the brain does not possess the classical lymphatic drainage system found in other parts of body. However, a recent letter in the journal Nature reports the discovery of lymphatic vessels lining the dural sinuses in mice. These were shown to drain immune cells and cerebrospinal fluid (CSF) into the deep cervical lymph nodes.

Although more work is yet to be done in humans, this discovery will cause neuroscientists to revisit a number of concepts related to CSF and lymphatic drainage, as well as immune functions in the brain.

For example, do these new data truly challenge the notion of immune privilege in the nervous tissue of the central nervous system—or do they apply to the brain as an organ and allow for lymphatic drainage of tissues outside the nervous tissue of the brain?

What can we use from this in teaching undergraduate A&P?

  • When discussing CSF drainage, consider mentioning the possibility that filtration of CSF directly into dural sinuses may be augmented by the newly discovered lymphatic drainage.

  • If you discuss the dogma of the "immune privilege" of the brain, consider mentioning this possible challenge to the concept. This may trigger a great discussion of whether these newly discovered lymphatic vessels are truly "in the brain."

  • If you discuss disorders involving altered immunity, such as multiple sclerosis, consider mentioning this discovery.

  • Bringing up this new information may be useful in discussions related to the process of science—how existing concepts are sometimes challenged by new information, for example. Perhaps a discussion of the need for more investigation would stimulate students to think about what future steps can be taken to map out a possible lymphatic network in or around the brain.
Current concept of lymphatic drainage (left) compared to updated version to reflect new data (right).

Want to know more?

Brain Drain | The brain contains lymphatic vessels similar to those found elsewhere in the body, a mouse study shows.
  • Ashley P. Taylor, The Scientist, June 1, 2015 (online)
  • Plain-English article summarizing the study and its significance.
Structural and functional features of central nervous system lymphatic vessels,
  • A. Louveau et al., Nature, June 1, 2015.doi:10.1038/nature14432, 
  • The original research article. Includes images and video.
Missing link found between brain, immune system; major disease implications
  • University of Virginia Health System, Science Daily, June 1, 2015
  • Illustrated press release describing the research.

Images: DBCLS (top)
Univ Va Health System (bottom)

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