Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Stanford study of sea squirt provides clue to human immune system

24.11.2005


"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.

Amy Adams | EurekAlert!
Further information:
http://www.stanford.edu
http://mednews.stanford.edu

More articles from Life Sciences:

nachricht Molecular Force Sensors
20.09.2017 | Max-Planck-Institut für Biochemie

nachricht Foster tadpoles trigger parental instinct in poison frogs
20.09.2017 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

Im Focus: Silencing bacteria

HZI researchers pave the way for new agents that render hospital pathogens mute

Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Molecular Force Sensors

20.09.2017 | Life Sciences

Producing electricity during flight

20.09.2017 | Power and Electrical Engineering

Tiny lasers from a gallery of whispers

20.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>