From the article:
One of the biggest challenges we face as a society is the eventual loss and degeneration of neurons from many causes, including many diseases – from Alzheimer’s disease to multiple sclerosis to Parkinson’s disease – and other sorts of injury.
To function in a cell, IL-6 has to bind in a specific place – called a “receptor site” – in a specific way. Dr. Rodriguez and colleagues were intrigued that IL-6 uses the same receptor site used by compounds whose job is to promote neuronal survival. “To me, that was pretty wild,” Dr. Rodriguez says. “So I hypothesized that maybe this IL-6 is also playing a role in protecting neurons.”
Testing this idea required extensive genetic work to produce different mouse groups that varied in their ability to produce IL-6. All were infected with a virus that causes a degenerative nerve disease. Animals with the IL-6 gene got mildly sick, but did not die. Mice lacking the IL-6 gene got severely sick and started dying. Why?
To find a cause of death, the Mayo Clinic team analyzed the animals' tissues. Their findings: neurons in the spinal cords of mice lacking IL-6 were degenerating dramatically. This evidence supported their hypothesis of a neuron-protection role for IL-6. It also led them to their next question: Where is IL-6 made?
An analysis of the brains of healthy mice possessing the IL-6 gene surprised them. “You look for IL-6 in the brain of a normal, healthy animal, and there is no IL-6 in a normal healthy animal!” Dr. Rodriguez says. “So then we infected the animals with the virus. Now when we looked for IL-6, guess what? It was everywhere.”
Specifically, IL-6 was found in astrocytes.