Tonsils Make T-Cells, Too

ScienceDaily (Mar. 5, 2012) — A new study provides evidence that a critical type of immune cell can develop in human tonsils. The cells, called T lymphocytes, or T cells, have been thought to develop only in the thymus, an organ of the immune system that sits on the heart.

The study, led by researchers at the Ohio State University Comprehensive Cancer Center -- Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCCC -- James), could improve the understanding of T-cell cancers and autoimmune diseases, and how stem-cell transplantation is done.
The study identified T cells at five distinct stages of development in the tonsil. These stages, identified using molecular signposts on the cells, were very similar to the stages of T-cell development in the thymus, although some differences were found as well.
The study also discovered that the cells develop in a particular region of the tonsil, in areas near the fibrous scaffold of the tonsil.
The findings are published in the Journal of Clinical Investigation.
"We've known for a long time that a functional thymus is necessary to develop a complete repertoire of T-cells, but whether a T-cell factory existed outside the thymus has been controversial," says principal investigator Dr. Michael A. Caligiuri, director of Ohio State's Comprehensive Cancer Center and CEO of the James Cancer Hospital and Solove Research Institute.
"I believe our study answers that question. It is the first report to describe a comprehensive, stepwise model for T-cell development outside the thymus."
It also raises a number of questions. Caligiuri notes that it's still unclear whether T-cells that develop in the tonsil also mature there or whether they leave the tonsil to mature elsewhere.
"The complete implications of this phenomenon for human health and disease are not entirely known," adds first-author Susan McClory, a graduate fellow in Caligiuri's laboratory. "It could be important in the development of T-cell cancers and autoimmune diseases, or it might suggest a location for T-cell development when thymus function is poor. We hope to do additional studies to explore these possibilities," she says.
Caligiuri, McClory and their colleagues conducted the study using tonsil tissue obtained from children undergoing routine tonsillectomy at Nationwide Children's Hospital in Columbus, and thymic tissue obtained from children undergoing thoracic surgery.
Using the molecular features of T-cells as they develop in the thymus, the researchers identified five populations of maturing T cells in the tonsils. They found, for example, that the first two of those groups resembled cells of the earliest stages of T cells that developed in the thymus, while cells in the fifth group were similar to nearly mature T-cells in the thymus.
They also showed that all five of the cell groups had the capacity to develop into T cells in laboratory tests, and that the first four populations had the capacity to develop into immune cells called natural killer cells.
"Overall, our work suggests that the tonsils serve as a T-cell factory, along with the thymus," Caligiuri says. "Next, we need to learn what proportion of T-cells is derived within the tonsil compared with the thymus."
Funding from the National Cancer Institute supported this research.
Other researchers involved in this study were Tiffany Hughes, Edward Briercheck, Chelsea Martin, Anthony J. Trimboli, Jianhua Yu, Xiaoli Zhang, Gustavo Leone and Gerard Nuovo of Ohio State University; and Aharon G. Freud of Stanford University.

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Eating Citrus Fruit May Lower Women's Stroke Risk

ScienceDaily (Feb. 23, 2012) — A compound in citrus fruits may reduce your stroke risk, according to research reported in Stroke: Journal of the American Heart Association. Eating higher amounts of a compound in citrus fruits, especially oranges and grapefruit, may lower ischemic stroke risk. Women who ate high amounts of the compound had a 19 percent lower risk of ischemic stroke than women who consumed the least amount.

This prospective study is one of the first in which researchers examine how consuming flavonoid subclasses affects the risk of stroke. Flavonoids are a class of compounds present in fruits, vegetables, dark chocolate and red wine.
"Studies have shown higher fruit, vegetable and specifically vitamin C intake is associated with reduced stroke risk," said Aedín Cassidy, Ph.D., the study's lead author and professor of nutrition at Norwich Medical School in the University of East Anglia in Norwich, United Kingdom.
"Flavonoids are thought to provide some of that protection through several mechanisms, including improved blood vessel function and an anti-inflammatory effect."
Cassidy and colleagues used 14-years of follow-up data from the Nurse's Health Study, which included 69,622 women who reported their food intake, including details on fruit and vegetable consumption every four years. Researchers examined the relationship of the six main subclasses of flavonoids commonly consumed in the U.S. diet -- flavanones, anthocyanins, flavan-3-ols, flavonoid polymers, flavonols and flavones -- with risk of ischemic, hemorrhagic and total stroke.
As expected, the researchers didn't find a beneficial association between total flavonoid consumption and stroke risk, as the biological activity of the sub-classes differ. However, they found that women who ate high amounts of flavanones in citrus had a 19 percent lower risk of blood clot-related (ischemic) stroke than women who consumed the least amounts.
In the study, flavanones came primarily from oranges and orange juice (82 percent) and grapefruit and grapefruit juice (14 percent). However, researchers recommended that consumers increase their citrus fruit intake, rather than juice, due to the high sugar content of commercial fruit juices.
A previous study found that citrus fruit and juice intake, but not intake of other fruits, protected against risk of ischemic stroke and intracerebral hemorrhage. Another study found no association between yellow and orange fruits and stroke risk, but did link increased consumption of white fruits like apples and pears with lower stroke risk. An additional study found that Swedish women who ate the highest levels of antioxidants -- about 50 percent from fruits and vegetables -- had fewer strokes than those with lower antioxidant levels.
More studies are needed to confirm the association between flavanone consumption and stroke risk, and to gain a better understanding about why the association occurs, the authors said.

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Can Chocolate Lower Your Risk of Stroke?

ScienceDaily (Feb. 11, 2010) — Eating chocolate may lower your risk of having a stroke, according to an analysis of available research that was released February 11 and will be presented at the American Academy of Neurology's 62nd Annual Meeting in Toronto April 10 to April 17, 2010. Another study found that eating chocolate may lower the risk of death after suffering a stroke.

The analysis involved reviewing three studies on chocolate and stroke.
"More research is needed to determine whether chocolate truly lowers stroke risk, or whether healthier people are simply more likely to eat chocolate than others," said study author Sarah Sahib, BScCA, with McMaster University in Hamilton, Ontario, Canada. Sahib worked alongside Gustavo Saposnik, MD, MSc, where the study was completed at St. Michael's Hospital and the University of Toronto.
Chocolate is rich in antioxidants called flavonoids, which may have a protective effect against stroke, but more research is needed.
The first study found that 44,489 people who ate one serving of chocolate per week were 22 percent less likely to have a stroke than people who ate no chocolate. The second study found that 1,169 people who ate 50 grams of chocolate once a week were 46 percent less likely to die following a stroke than people who did not eat chocolate.
The researchers found only one additional relevant study in their search of all the available research. That study found no link between eating chocolate and risk of stroke or death.