Featured Research

from universities, journals, and other organizations

'Killer' B Cells Demonstrate Evolutionary Link Between Fish And Mammal Immune Systems

Date:
September 23, 2006
Source:
University of Pennsylvania
Summary:
Researchers from the University of Pennsylvania School of Veterinary Medicine have discovered a unique evolutionary link between the immune systems of fish and mammals in the form of a primitive version of B cells, white blood cells of the immune system. Unlike mammalian B cells, which produce antibodies, these "killer" B cells actually ingest foreign particles and microbes. The finding represents a sizeable evolutionary step and offers a potential strategy for developing needed fish vaccines.

In the adaptive immune system in mammals, B cells produce antibodies to fight infection. In the more-primitive innate immunity in fish, scientists found that B cells take part in a process known as phagocytosis, by which immune system cells ingest foreign particles and microbes. The round cell in the lower left is B-cell ike from a trout. It is in the process of engulfing three latex beads, each (arrow) about 1 micron in diameter.
Credit: J. Oriol Sunyer, School of Veterinary Medicine, University of Pennsylvania; image taken with the assistance of R. Meade, Biomedical Imaging Core Laboratory of the School of Medicine, University of Pennsylvania

Researchers from the University of Pennsylvania School of Veterinary Medicine have discovered a unique evolutionary link between the immune systems of fish and mammals in the form of a primitive version of B cells, white blood cells of the immune system. Their studies link the evolution of the adaptive immune system in mammals, where B cells produce antibodies to fight infection, to the more primitive innate immunity in fish, where they found that B cells take part in phagocytosis (literally: cell eating), the process by which cells of the immune system ingest foreign particles and microbes.

The finding, which appears in the online version of Nature Immunology and will be featured on the cover of the October issue, represents a sizeable evolutionary step for the mammalian immune system and offers a potential new strategy for developing much-needed fish vaccines.

"When examining fish B cells we see them actively attacking and eating foreign bodies, which is a behavior that, according to the current dogma, just shouldn't happen in B cells," said J. Oriol Sunyer, a professor in Penn Vet's Department of Pathobiology. "I believe it is evidence for a very real connection between the most primitive forms of immunological defense, which has survived in fish, and the more advanced, adaptive immune response seen in humans and other mammals."

About 400 million years ago, the earliest ancestors of modern fish split off of the evolutionary pathway that became the earliest ancestors of modern mammals. In modern mammals, the B cell is a highly adapted part of the immune system chiefly responsible for, among other things, the creation of antibodies that tag foreign particles and microbes for destruction. Mammals have phagocytic cells, but they are a specialized few cells identified apart from the complex interactions that drive other white blood cells.

Sunyer and his colleagues discovered this previously unsuspected B cell activity while examining the immune cells of rainbow trout and catfish. The researchers determined that these attack B cells account for more than 30-40% of all immune cells in fish, while phagocytic cells only make up a small portion of the total number of immune cells in mammals. Further research also showed that a significant portion of amphibian B cells retained their digestive traits.

"The immune systems of amphibians and fish are far less advanced than ours," Sunyer said. "When you only have a rudimentary adaptive immune system, it helps to have more phagocytic cells to compensate, which is what has served fish so well over the last 400 million years."

In the past, research on the immune systems of more primitive species has paved the way to the discovery of new molecules and pathways that are critical to the immune response in humans and other mammals. B cells themselves, for example, were first discovered in chickens in the 1960s. According to Sunyer, the Penn findings are not only important for understanding the evolution and function of immune cells in fish but also may point out to novel roles of B cells in mammals.

At this point, we cannot rule out the possibility that small subpopulations of phagocytic B cells, perhaps remnants of those present in fish, are still present in mammals, Sunyer said.

Their findings also have an agricultural implication. The current vaccines given to farmed salmon, for example, appeal to the fish's adaptive immune response, which this research has now shown to be a smaller part of the overall fish immune system than previously thought.

"If we work to create vaccines that encourage phagocytic B cell to respond to infection, then we would play to the strengths of fish immunity," Sunyer said. "In the long term, farming is a better, more environmentally sound approach to fishing, so better vaccines may make the practice more financially attractive to fisherman and less destructive to fish populations."

There is little doubt that, despite the behavioral differences, the fish B cells represent a less advanced version of mammalian B cells. Sunyer found the very cellular structures that medical science has used to define B cells in humans to be present in fish B cells, which is why they are able to label them as B cells in the first place.

"Here we have a clear picture of where one part of the immune system, primitive phagocytes, adapted over time to serve a more complex role as part of the immune system that humans enjoy today, Sunyer said. There is still much we can learn about our own health through the ongoing study of immune system evolution among all organisms.

Funding for this research was provided by the National Science Foundation and United States Department of Agriculture.


Story Source:

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


Cite This Page:

University of Pennsylvania. "'Killer' B Cells Demonstrate Evolutionary Link Between Fish And Mammal Immune Systems." ScienceDaily. ScienceDaily, 23 September 2006. <www.sciencedaily.com/releases/2006/09/060920191637.htm>.
University of Pennsylvania. (2006, September 23). 'Killer' B Cells Demonstrate Evolutionary Link Between Fish And Mammal Immune Systems. ScienceDaily. Retrieved September 22, 2014 from www.sciencedaily.com/releases/2006/09/060920191637.htm
University of Pennsylvania. "'Killer' B Cells Demonstrate Evolutionary Link Between Fish And Mammal Immune Systems." ScienceDaily. www.sciencedaily.com/releases/2006/09/060920191637.htm (accessed September 22, 2014).

Share This



More Health & Medicine News

Monday, September 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Liberia Pleads for Help to Fight Ebola

Liberia Pleads for Help to Fight Ebola

AP (Sep. 22, 2014) Liberia's finance minister is urging the international community to quickly follow through on pledges of cash to battle Ebola. Bodies are piling up in the capital Monrovia as the nation awaits more help. (Sept. 22) Video provided by AP
Powered by NewsLook.com
Global Ebola Aid Increasing But Critics Say It's Late

Global Ebola Aid Increasing But Critics Say It's Late

Newsy (Sep. 21, 2014) More than 100 tons of medical supplies were sent to West Africa on Saturday, but aid workers say the global response is still sluggish. Video provided by Newsy
Powered by NewsLook.com
Sierra Leone in Lockdown to Control Ebola

Sierra Leone in Lockdown to Control Ebola

AP (Sep. 21, 2014) Sierra Leone residents remained in lockdown on Saturday as part of a massive effort to confine millions of people to their homes in a bid to stem the biggest Ebola outbreak in history. (Sept. 20) Video provided by AP
Powered by NewsLook.com
Sierra Leone's Nationwide Ebola Curfew Underway

Sierra Leone's Nationwide Ebola Curfew Underway

Newsy (Sep. 20, 2014) Sierra Leone is locked down as aid workers and volunteers look for new cases of Ebola. 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