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Researchers discover immunity mechanism: Platelets patrolling the bloodstream

Date:
June 19, 2013
Source:
University of Calgary
Summary:
Scientists have discovered a mechanism that is used to protect the body from harmful bacteria. Platelets, a component of blood typically associated with clotting, were discovered to actively search for specific bacteria, and upon detection, seal it off from the rest of the body. The findings provide the science community with a greater understanding of immunity.

Within the liver, platelets (red) are seen to actively patrol for bacteria. This searching process involves short, “touch-and-go” interactions between the platelet and Kupffer cells (blue), a specialized immune cell that lives in the blood vessels of the liver.
Credit: Courtesy Faculty of Medicine video

Scientists at the University of Calgary's Faculty of Medicine have discovered a mechanism that is used to protect the body from harmful bacteria. Platelets, a component of blood typically associated with clotting, were discovered to actively search for specific bacteria, and upon detection, seal it off from the rest of the body.

The findings, which were published in Nature Immunology this week, provide the science community with a greater understanding of immunity.

"The science community has known that platelets do participate in immunity, but now it's been demonstrated that they have a way of actively searching for bacteria," says Craig Jenne, PhD, one of the authors of the study and a member of the university's Snyder Institute for Chronic Diseases.

The vast majority of bacteria in the blood stream is trapped by the liver in a network of specialized cells known as Kupffer cells. Once trapped, a series of immune processes take place to eradicate the bacteria; however, this can take several hours, lending time to harmful bacteria to multiply and release toxins into the neighboring cells, subsequently causing infection and cell damage and death.

"Upon entering the blood stream, bacteria can start to divide within several minutes," he says. "So if you're waiting for the immune system to deal with it, the bacteria could become an infection before it gets there."

Through imaging of the liver in animal models, scientists discovered that platelets are constantly interacting with the Kupffer cells by 'touching' them to search for captured bacteria. If nothing is detected, or if the bacteria isn't deemed particularly harmful, the platelets will move on; however, if harmful bacteria is detected, the platelets will bind to it, sealing it off from the body until the immune system can rid the bacteria altogether. This happens within seconds of cell capture and thus reduces the likelihood of infection.

"If this instantaneous response didn't exist, it could be a matter of life and death," he says.

Interestingly, it was observed that while this touch-and-go mechanism is happening continuously, platelets only appear to create this barrier around particularly harmful bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA). MRSA can lead to serious and potential fatal conditions such as sepsis, and is spread through skin to skin contact.

"We now have a completely different angle of how the immune system deals with specific types of bacteria," says study author Paul Kubes, PhD, who is also director of the Snyder Institute for Chronic Diseases. "Going forth we can begin to look at how we can help our own defenses deal with these types of bacteria."

Video: http://www.youtube.com/watch?v=cUpIkSXoQUY


Story Source:

The above story is based on materials provided by University of Calgary. The original article was written by Kathryn Sloniowski. Note: Materials may be edited for content and length.


Journal Reference:

  1. Connie H Y Wong, Craig N Jenne, Björn Petri, Navina L Chrobok, Paul Kubes. Nucleation of platelets with blood-borne pathogens on Kupffer cells precedes other innate immunity and contributes to bacterial clearance. Nature Immunology, 2013; DOI: 10.1038/ni.2631

Cite This Page:

University of Calgary. "Researchers discover immunity mechanism: Platelets patrolling the bloodstream." ScienceDaily. ScienceDaily, 19 June 2013. <www.sciencedaily.com/releases/2013/06/130619101646.htm>.
University of Calgary. (2013, June 19). Researchers discover immunity mechanism: Platelets patrolling the bloodstream. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2013/06/130619101646.htm
University of Calgary. "Researchers discover immunity mechanism: Platelets patrolling the bloodstream." ScienceDaily. www.sciencedaily.com/releases/2013/06/130619101646.htm (accessed July 28, 2014).

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