PROVIDENCE, R.I. [Brown University] The immune system maintains a rich abundance of "natural killer" cells to confront microbial invaders, but as the body gains the upper hand in various infections it sometimes starts to produce even more of the cells. For three decades, scientists haven't understood what purpose that serves. In a new paper, Brown University researchers show one: proliferation helps change the NK cells' function from stimulating the immune response to calming it down, lest it get out of hand.
In a series of experiments now published online in the Journal of Immunology, the researchers show that the process of proliferation unlocks expression of the gene in NK cells for producing Interleukin-10(IL-10), a protein that moderates other immune system cells.
"It's really important for regulating potentially dangerous CD8 T cell responses," said Margarite Tarrio, co-lead author of the paper and a graduate student in the lab of Brown immunology Professor Christine Biron. "If you get CD8 T cells that are hyperactivated they can cause a tremendous amount of damage."
Ever since Biron and colleagues published the first observations of NK cell proliferation in 1982, she has sought to figure out why it happens. Knowing the answer is important both as a matter of basic immunology and because NK cells, as crucial members of the body's first line of infection defense, are often the subjects of efforts to harness the immune system in protection against infections and cancer.
"The work provides another important role for lymphocyte proliferation, to set up the conditions needed for changing function," Biron said. "It is likely to be part of the mechanism for changing the functions of other immune cells, and the insight may help in designing vaccines."
Shown down to the gene
An association between NK cells and IL-10 production doesn't necessarily emerge in all infections,
|Contact: David Orenstein|