Low-profile organ plays a big role in immune response, study finds,,
THURSDAY, July 30 (HealthDay News) -- Though its reputation doesn't rank down there with the appendix, the spleen isn't exactly known as a vital organ. In fact, plenty of people do fine without it.
But new research suggests the spleen plays a bigger role in the immune system than previously thought.
In mice, scientists found, the spleen serves as a home for a type of white blood cell that scavenges dead tissue and helps produce inflammation, which contributes to healing. In particular, the researchers discovered that the spleen helps the heart recover from disease.
"While the spleen may not be essential for your survival, it plays a crucial role once you are sick," said study author Filip K. Swirski, an immunology instructor at Harvard Medical School.
The findings could lead to a better understanding of the immune system, including its response to cancer, Swirski said. And it definitely improves the profile of a little-understood organ.
It's much more obscure than, say, the liver or kidneys, but the spleen still takes up a lot of space. In humans, it's about the size of a large eggplant and shaped like a kidney, Swirski said.
Scientists have known that the spleen recycles red blood cells and scans the blood for germs. "It serves as a filtering system," Swirski said. "It captures viruses or bacteria, and can elicit an inflammatory response."
Inflammation -- think of the redness around a wound -- indicates that the immune system is rushing in to defend the body.
But people often do just fine without their spleens. Traumatic injuries, such as those sustained in traffic accidents, often result in surgery to remove the spleen. And surgeons remove spleens from people with some medical conditions, including non-Hodgkin lymphoma.
In their study, the researchers examined mice to see if having a spleen helped the mice recover from induced heart disease. A 1977 study of veterans who'd had their spleens removed suggested they had twice the risk of dying of heart disease, Swirski said.
They found that the spleen did indeed appear to help the heart, through white-blood cells known as monocytes. The spleen served as a home for many of the cells, Swirski said.
A report on the study appears in the July 31 issue of Science.
"This just adds another function to the spleen," Swirski said. "It's not only a place where blood cells come to die and where the immune system screens for infection. It's relevant to how the immune system is mobilized."
Future research could explore how to boost the spleen's role in the immune system's response or keep it from being hijacked by germs, he added.
In a commentary accompanying the study, two doctors from Memorial Sloan-Kettering Cancer Center in New York City suggest the spleen is still as "dispensable," despite the new findings. But, they wrote, the spleen does seem "a bit more purposeful and deserving of recognition."
The Journal of the American Medical Association has more about the spleen.
SOURCE: Filip K. Swirski, Ph.D., instructor, immunology, Harvard Medical School, Boston; July 31, 2009, Science
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