Navigation Links
Bacteria-killing proteins cover blood type blind spot
Date:2/14/2010

A set of proteins found in our intestines can recognize and kill bacteria that have human blood type molecules on their surfaces, scientists at Emory University School of Medicine have discovered.

The results were published online Feb. 14 and are scheduled to appear in the journal Nature Medicine.

Many immune cells have receptors that respond to molecules on the surfaces of bacteria, but these proteins are different because they recognize structures found on our own cells, says senior author Richard D. Cummings, PhD, professor and chair of the Department of Biochemistry. "It's like having a platoon in an army whose sole purpose is to track down enemy soldiers that are wearing the home country's uniforms."

Blood type comes from differences in sugar molecules attached to proteins on red blood cells. If incompatible blood types are mixed, the antibodies from one person will make red blood cells from the other person clump together, with devastating results in an emergency. But someone's immune system usually doesn't make antibodies to the sugar molecules on his or her own red blood cells. That creates a potential blind spot that bacteria could exploit.

For example, a strain of E. coli (O86) has molecules on its surface like those in humans with blood type B. People with blood type B are unable to produce antibodies against E. coli O86. Although O86 is known to infect birds, it's not a major danger like other types of E. coli, some of which can cause severe diarrhea.

Cummings and his colleagues wanted to know why more bacteria haven't adopted the tactics of E. coli O86 to get around the immune system. Searching for proteins that could bind to the sugar molecules characteristic of blood types A and B, graduate students Sean Stowell, PhD, and Connie Arthur identified proteins called galectin-4 and galectin-8.

"These proteins are separate from antibodies and other parts of the immune system," Cummings says. "They kill bacteria like E. coli O86 all by themselves within a couple of minutes."

When E. coli O86 is exposed to these proteins and viewed by electron microscopy, "it looks as if somebody is tearing away at their outer membranes," he adds.

However, galectins-4 and -8 did not kill human red blood cells expressing blood group antigens. High levels of lactose (milk sugar) can inhibit the lethal activity of these galactins, whereas sucrose (cane sugar) does not.

"This raises the question of whether there are dietary effects, as from milk sugars or other dietary polysaccharides, that might inhibit activity of these galectins on intestinal microbes and their proliferation and colonization," Cummings says.

Cummings notes the unique properties of galectins-4 and -8 may provide an explanation for why the human population has such a diversity of sugar molecules on blood cells. The diversity may ensure that some part of the population might be able to fend off a bacterial infection. For example, ABO blood type seems to affect susceptibility to Helicobacter pylori, a bacterium linked to ulcers.

Galectins were thought to have evolved long before "adaptive immunity," the part of vertebrates' immune systems that is responsible for producing a variety of antibodies. Galectins may have allowed the generation of a diverse group of blood type sugar molecules in human tissues as a safe set of molecules to evolve because immunity is backstopped by galectins, Cummings says.

Galectins-4 and-8 were also able to kill another variety of E. coli that display a sugar molecule found on many mammalian cells, although more protein was needed. That leads to a question Cummings and his colleagues are investigating now: What else do galectins recognize, and how does that constrain the kinds of bacteria that can live in our intestines? In addition, it may now be possible, given these results, to engineer molecular changes in these galectins to allow them to kill other types of pathogenic bacteria that display other types of sugar molecules on their surface. Such developments could lead to new types of antibiotics for pathogenic microbes.


'/>"/>

Contact: Holly Korschun
hkorsch@emory.edu
404-727-3990
Emory University
Source:Eurekalert

Related biology news :

1. Researchers identify proteins involved in new neurodegenerative syndrome
2. NIH awards researcher $1.5 million new innovator grant for fruit-fly studies of prion proteins
3. Depression, aging, and proteins made by a virus may all play role in heart disease
4. New approach builds better proteins inside a computer
5. Legionnaires bacterial proteins work together to survive
6. Proteins pack tighter in crowded native state
7. MIT IDs proteins key to brain function
8. Cystic fibrosis proteins photographed interacting
9. Using carbon nanotubes to seek and destroy anthrax toxin and other harmful proteins
10. The precise role of seminal proteins in sustaining post-mating responses in fruit flies
11. Carnegie Mellon scientists develop fluorescent proteins for live cell imaging, biosensor design
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/22/2016)... , Jan. 22, 2016 ... addition of the "Global Biometrics Market ... their offering. --> http://www.researchandmarkets.com/research/p74whf/global_biometrics ... "Global Biometrics Market in Retail Sector ... --> Research and Markets ( ...
(Date:1/20/2016)... 20, 2016   MedNet Solutions , an innovative ... of clinical research, is pleased to announce the attainment ... are the result of the company,s laser focus on ... , it,s comprehensive, easy-to-use and highly affordable cloud-based ... Key MedNet growth achievements in 2015 include: ...
(Date:1/15/2016)... , Jan. 15, 2016 Recent publicized breaches ... to find new ways to ensure data security and ... iOS and Android that ties a ... transforming it into a hardware authorization token. Customer service ... their fingerprint on their KodeKey enabled device to verify ...
Breaking Biology News(10 mins):
(Date:2/10/2016)... ANNAPOLIS, Md. , Feb. 10, 2016  The ... E. Busch , has announced that University of Maryland ... MD, PhD, MBA and University of Maryland Medical System ... recipients of the "Speaker,s Medallion," the highest honor given ... House of Delegates. Dean Reece and ...
(Date:2/10/2016)... Feb. 10, 2016  IsoRay, Inc. (NYSE MKT: ISR), ... and medical radioisotope applications for the treatment of prostate, ... announced its financial results for the second quarter and ... 2015. --> --> ... of fiscal 2016, which ended December 31, 2015, a ...
(Date:2/10/2016)... ... February 10, 2016 , ... HOLLOWAY AMERICA, a leading custom ... Rocky Mountain Chapter 21st Annual Vendor Exhibition on Thursday, February 18, 2016. The ... for its annual event, which will run from 3:00 p.m. - 8:30 p.m. ...
(Date:2/10/2016)... ... 10, 2016 , ... Curoverse announced today that the open-source, ... capabilities for managing and processing genomic and health data at petabyte scale. ... and analyzing genomic data,” said Adam Berrey chief executive officer at Curoverse. “Microsoft ...
Breaking Biology Technology: