Featured Research

from universities, journals, and other organizations

Stanford Study Of Sea Squirt Provides Clue To Human Immune System

Date:
November 24, 2005
Source:
Stanford University Medical Center
Summary:
The trigger for this unseemly behavior has now been traced to a single gene, isolated by researchers at the Stanford University School of Medicine. That gene also points to a common origin with the vertebrate immune system, far back in animal evolution, potentially shedding light on the development of our own immune system.

Botryllus schlosseri.
Credit: Photo Source: MIT Sea Grant College Program

STANFORD, Calif. - "You can eat your relatives but not your friends," could be the off-kilter credo of a tiny marine invertebrate called a sea squirt that can physically merge with, and parasitize, its own kin. The trigger for this unseemly behavior has now been traced to a single gene, isolated by researchers at the Stanford University School of Medicine. That gene also points to a common origin with the vertebrate immune system, far back in animal evolution, potentially shedding light on the development of our own immune system.

The sea squirt with the questionable philosophy is Botryllus schlosseri, a colonial animal that looks deceptively like a small flower. Each of its apparent petals is actually a separate, though genetically identical, organism, linked to the others by a common blood vessel. Ringing the tiny petals are even tinier tentacle-like ampullae, the sensing organs that evaluate other sea squirts, determining who's related and who isn't.

If two adjacent squirts aren't related, their respective ampullae blacken and shrivel upon contact. But when the squirts are related, they begin to physically fuse together. Thus, the ampullae had to be able to sense genetic similarity among sea squirts, said Anthony De Tomaso, PhD, researcher in pathology and first author of a paper on the subject in the Nov. 24 issue of Nature. "We were looking for the genes which control how an individual can distinguish self from non-self," he said.

Fusing together benefits the filter-feeding squirts because they live in high-density areas such as marinas, where competition among sea life is fierce. Because adult squirts are sedentary, if the area around them is already occupied, they can only increase their feeding area by fusing.

The downside of fusing is that one sea squirt can parasitize the other, essentially taking over its body by means of mobile stem cells, which transplant themselves between the fused individuals through the shared circulatory system. Eventually one set of stem cells overpowers the other, going on to replace the tissues of the loser. It was the fusing process, body-snatching tendencies notwithstanding, that attracted De Tomaso's interest.

De Tomaso and senior author Irving Weissman, MD, the Virginia and D.K. Ludwig Professor for Clinical Investigation in Cancer Research and director of the Stanford Institute for Stem Cell Biology and Regenerative Medicine, knew that the sea squirts' ability to sense who was fusible appeared to bear strong similarities to certain cells in our own immune system, called natural killer cells. Like Botryllus, natural killer cells only recognize genetically similar material. Anything they don't recognize, they attack, as often occurs in bone marrow transplants.

Through a long process of sorting and testing, De Tomaso's team isolated the controlling gene. "We found a gene which by itself predicts whether two colonies will fuse or reject," he said, adding, "Now we have the first piece of the puzzle of understanding how this happens on a molecular level."

The gene is an immunoglobulin, the type of gene that makes up the entire human immune system. "This is the first time we've seen a connection between these two systems," said De Tomaso. Until now, no one had demonstrated any concrete similarity between the vertebrate and invertebrate immune systems. The ramifications of the finding may shed light not only on the evolution of our immune system, but also on how we might better control some aspects of it, such as our natural killer cells.

"If you could teach those natural killer cells to be tolerant, you could transplant bone marrow between any two people, a huge first step in curing diseases like leukemia," said De Tomaso. Learning how to manipulate our immune systems would also have major ramifications for treating autoimmune diseases such as multiple sclerosis, which essentially represents a breakdown of recognition by the immune system, attacking the body it should be defending.

De Tomaso's team is already working on the next step in sorting out the workings of Botryllus' immune system-deciphering the actual molecular mechanism by which the sea squirt ascertains which of its neighbors shares its urge to merge, in spite of the risks.

###

Also participating in the project were Stephen V. Nyholm, Karla J. Palmeri, Katherine J. Ishizuka, William B Ludington and Katrina Mitchel, all of Stanford University School of Medicine, Departments of Pathology and Developmental Biology and Hopkins Marine Station, Department of Biology.

This study was supported by grants from the National Institutes of Health and the Community Sequencing Program at the Department of Energy Joint Genome Institute.

Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital at Stanford. For more information, please visit the Web site of the medical center's Office of Communication & Public Affairs at http://mednews.stanford.edu


Story Source:

The above story is based on materials provided by Stanford University Medical Center. Note: Materials may be edited for content and length.


Cite This Page:

Stanford University Medical Center. "Stanford Study Of Sea Squirt Provides Clue To Human Immune System." ScienceDaily. ScienceDaily, 24 November 2005. <www.sciencedaily.com/releases/2005/11/051124110817.htm>.
Stanford University Medical Center. (2005, November 24). Stanford Study Of Sea Squirt Provides Clue To Human Immune System. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2005/11/051124110817.htm
Stanford University Medical Center. "Stanford Study Of Sea Squirt Provides Clue To Human Immune System." ScienceDaily. www.sciencedaily.com/releases/2005/11/051124110817.htm (accessed July 30, 2014).

Share This




More Health & Medicine News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Generics Eat Into Pfizer's Sales

Generics Eat Into Pfizer's Sales

Reuters - Business Video Online (July 29, 2014) Pfizer, the world's largest drug maker, cut full-year revenue forecasts because generics could cut into sales of its anti-arthritis drug, Celebrex. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Nigeria Ups Ebola Stakes on 1st Death

Nigeria Ups Ebola Stakes on 1st Death

Reuters - Business Video Online (July 29, 2014) Nigerian authorities have shut and quarantined a Lagos hospital where a Liberian man died of the Ebola virus, the first recorded case of the highly-infectious disease in Africa's most populous economy. David Pollard reports Video provided by Reuters
Powered by NewsLook.com
Running 5 Minutes A Day Might Add Years To Your Life

Running 5 Minutes A Day Might Add Years To Your Life

Newsy (July 29, 2014) According to a new study, just five minutes of running or jogging a day could add years to your life. Video provided by Newsy
Powered by NewsLook.com
Ebola Outbreak Poses Little Threat To U.S.: CDC

Ebola Outbreak Poses Little Threat To U.S.: CDC

Newsy (July 29, 2014) The Ebola outbreak in West Africa poses little threat to Americans, according to officials with the Centers for Disease Control and Prevention. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins