Featured Research

from universities, journals, and other organizations

Humans and sharks share immune system feature

Date:
September 30, 2011
Source:
National Jewish Health
Summary:
A central element of the immune system has remained constant through more than 400 million years of evolution, according to new research. T-cell receptors from mice continue to function even when pieces of shark, frog and trout receptors are substituted in. The function of the chimeric receptors depends on a few crucial amino acids, found also in humans, that help the T-cell receptor bind to MHC molecules presenting antigens.

Evolution of adaptive immune system.
Credit: Image courtesy of National Jewish Health

A central element of the immune system has remained constant through more than 400 million years of evolution, according to new research at National Jewish Health. In the September 29, 2011, online version of the journal Immunity, the researchers report that T-cell receptors from mice continue to function even when pieces of shark, frog and trout receptors are substituted in. The function of the chimeric receptors depends on a few crucial amino acids, found also in humans, that help the T-cell receptor bind to MHC molecules presenting antigens.

"These findings prove a hypothesis first proposed 40 years ago," said senior author Laurent Gapin, PhD, associate professor of immunology in the Integrated Deparemtn of Immunology at National Jewish Health and the University of Colorado Denver. "Even though mammals, amphibians and cartilaginous fish last shared a common ancestor more than 400 million years ago, they continue to share an element of their T-cell receptors, indicating that the T cell-MHC interaction arose early in the evolution of the immune system, and is central to its function."

The T cell serves as the sentinel, manager and enforcer of the adaptive immune response. It relies on its receptor, the T-cell receptor, to recognize foreign material and identify the target of the immune-system attack. When the receptor binds to small fragments of foreign organisms, called antigens, the T cell becomes activated, proliferates and initiates an attack against any molecule or organism containing that antigen.

T cells, however, cannot recognize free-floating antigens. They recognize antigens only when they are held by MHC molecules on the surfaces of other cells, much as a hotdog bun (MHC molecule) holds a hotdog (antigen). This interaction between the T cell and MHC molecules is crucial for immune defense and organ transplants. Compatibility of transplanted organs is determined by the similarity of different people's MHC molecules. Nonetheless, this interaction has long mystified scientists and is poorly understood.

In 1971 future Nobel Laureate Niels K. Jerne proposed that evolution might have selected for genes that specifically recognize MHC molecules. Evidence discovered later suggested T cells' affinity for MHC molecules might instead be the product of development that occurs as T cells mature in the thymus. The question remained unanswered for 40 years.

The T-cell receptor is constructed by piecing together several peptides among dozens that are available, plus a few random amino acid sequences. This combination is what allows the immune system to generate an almost infinite variety of receptors capable of recognizing almost any potential invader. The receptor has six loops that are the primary binding points for the antigen-MHC complex. One of those loops, known as CDR2, frequently binds the MHC molecule.

Searching for possible similarities in T-cell receptors of different animals, the researchers compared the amino acid sequences of one segment of the T-cell receptor containing the CDR2 loop. Although the segments contained less than 30 percent of the same amino acids, two specific amino acids were the same in human, mouse, frog, trout and shark T-cell receptors. Those appeared to be amino acids specifically involved in binding to the MHC molecule.

"The evolutionary inheritance of this pattern goes all the way from sharks to humans, which last shared a common ancestor 450 million years ago," said co-author Philippa Marrack, PhD.

The researchers then inserted segments containing the CDR2 loop from frog, trout and shark T-cell receptors into mouse cells. These chimeric T-cell receptors recognized antigen bound to a mouse MHC molecule.

Since sections of frog, trout and shark T-cell receptors functioned perfectly well in mice T-cell receptors, the experiments suggested that the T-cell's ability to see an antigen only when complexed with an MHC molecule first arose more than 400 million years ago, when all four animals shared a common ancestor.


Story Source:

The above story is based on materials provided by National Jewish Health. Note: Materials may be edited for content and length.


Journal Reference:

  1. JamesP. Scott-Browne, Frances Crawford, MaryH. Young, JohnW. Kappler, Philippa Marrack, Laurent Gapin. Evolutionarily Conserved Features Contribute to αβ T Cell Receptor Specificity. Immunity, 2011; DOI: 10.1016/j.immuni.2011.09.005

Cite This Page:

National Jewish Health. "Humans and sharks share immune system feature." ScienceDaily. ScienceDaily, 30 September 2011. <www.sciencedaily.com/releases/2011/09/110930093532.htm>.
National Jewish Health. (2011, September 30). Humans and sharks share immune system feature. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2011/09/110930093532.htm
National Jewish Health. "Humans and sharks share immune system feature." ScienceDaily. www.sciencedaily.com/releases/2011/09/110930093532.htm (accessed July 28, 2014).

Share This




More Plants & Animals News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com
Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Newsy (July 27, 2014) The satellite is back under ground control after a tense few days, but with a gecko sex experiment on board, the media just couldn't help themselves. Video provided by Newsy
Powered by NewsLook.com
Trees Could Save More Than 850 Lives Each Year

Trees Could Save More Than 850 Lives Each Year

Newsy (July 27, 2014) A national study conducted by the USDA Forest Service found that trees collectively save more than 850 lives on an annual basis. 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