To find out what had changed in the brains of the infected rats, the team used techniques borrowed from immunology to sort out one specific cell type from brain tissue rapidly enough that they could see what the cells had been doing.
The work adds to an emerging picture of glial cells acting in the brain much the same way immune system macrophages operate elsewhere in the body gobbling up other cells and tearing them apart. The glia also perform a pruning function to streamline the brain's neural architecture as it matures. But some brain disorders appear to be a case of dysfunctional pruning, Bilbo said.
To test how the immune response affected memory, Bilbo's team placed all the rats in a novel environment and exposed them to a sound and a mild shock through their feet. A normal rat remembers the environment after one trial, freezing in place immediately when they enter the familiar setting a second time.
But rats exposed to infection, who tend to overproduce IL-1, stroll through the previously painful experience as if they've never seen it before, Bilbo said.
Even without experiencing the second immune challenge, the rats infected as youngsters also seem to show cognitive declines earlier than their normal control counterparts. "This is intriguingly similar to what you see in Alzheimer's. It's really kind of scary," Bilbo said.
"These findings could help us understand why some humans are more vulnerable than others to cognitive impairments from chronic infections, aging and neurodegenerative diseases such as Alzheimer's disease," said Raz Yirmiya, a professor of psychobiology at the Hebrew University of Jerusalem, who was not involved in the research. "This might also lead to new approaches toward diagnostic, preventive and therapeutic procedures for these conditions."
Any illness that triggers an immune response tends to slow a person'
|Contact: Karl Leif Bates|