Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Bacteria-killing proteins cover blood type blind spot

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.

The research was supported by the National Institute of General Medical Sciences of the National Institutes of Health and the Consortium for Functional Glycomics and also involved key contributions from Marcelo Dias-Baruffi, PhD, and colleagues at the Universidade de São Paolo in Ribeirão Preto, Brazil.

Reference: S.R. Stowell et al. Innate immune lectins kill bacteria expressing blood group antigen. Nat. Med. 16, page numbers (2010).

The Robert W. Woodruff Health Sciences Center of Emory University is an academic health science and service center focused on missions of teaching, research, health care and public service. Its components include the Emory University School of Medicine, Nell Hodgson Woodruff School of Nursing, and Rollins School of Public Health; Yerkes National Primate Research Center; Winship Cancer Institute of Emory University; and Emory Healthcare, the largest, most comprehensive health system in Georgia. Emory Healthcare includes: The Emory Clinic, Emory-Children's Center, Emory University Hospital, Emory University Hospital Midtown, Wesley Woods Center, and Emory University Orthopaedics & Spine Hospital. The Woodruff Health Sciences Center has $2.3 billion in operating expenses, 18,000 employees, 2,500 full-time and 1,500 affiliated faculty, 4,500 students and trainees, and a $5.7 billion economic impact on metro Atlanta.

Learn more about Emory's health sciences: - @emoryhealthsci (Twitter) -

Holly Korschun | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Novel mechanisms of action discovered for the skin cancer medication Imiquimod
21.10.2016 | Technische Universität München

nachricht Second research flight into zero gravity
21.10.2016 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>