Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers explore new driver of transplant rejection: Platelets

20.02.2009
“Platelet guy” at Johns Hopkins finds there’s a lot more to these cells than blood clotting

Platelets, tiny and relatively uncharted tenants of the bloodstream known mostly for their role in blood clotting, turn out to also rally sustained immune system inflammatory responses that play a critical role in organ transplant rejection, according to a new report from Johns Hopkins scientists.

“Platelets potentially hold sway over many aspects of transplant biology,” says Craig Morrell, D.V.M., Ph.D., an assistant professor of molecular and comparative pathobiology at the Johns Hopkins University School of Medicine. “Our data, as well as others’, show a surprising interplay of platelets and the immune system, so it’s time for the transplant world at large to have platelets on its radar.”

A self-described “platelet guy” transfixed by the unexplored biology of these circulating bodies, Morrell collaborated with clinicians in the fields of transplant to write a comprehensive review of platelets and transplant biology, published in the January issue of the American Journal of Transplantation.

“It all began with the observation that when transplant tissue is rejected, platelets line up in the interior of blood vessels feeding the tissue,” Morrell says. “It turns out they are not just bystanders, but have a role in driving that rejection.”

As one of the most abundant cell types in the blood — second only to the oxygen-carrying red variety — platelets are ubiquitous but relatively unexplored, Morrell says. “It’s crazy how many potentially active molecules are jam-packed in these small cells and that we’re only just beginning to appreciate their pro-inflammatory qualities.”

In fact, mounting evidence from Morrell and others shows that platelets are part of a sustained and general immune response that can trigger or exacerbate organ rejection. Not only do they rush to the scene of a wound and adhere to local blood vessels, preventing fatal bleeding, they also dump out granules that “talk to” immune system white blood cells, Morrell says, recruiting them from far and wide to stave off potential infections.

These are on the whole very good things for platelets to do, Morrell says, but in the context of organ transplants, their pro-inflammatory function gets out of control, and they do more bad than good after contributing to initial wound healing.

Strategies using drugs or other means to keep platelets quiet and non-inflammatory might benefit transplant patients in the long run because chronic rejection — as contrasted with acute or immediate organ rejection — is a major complication for which there is little current treatment, according to Hamid Rabb, M.D., medical director of kidney transplantation and a professor of medicine at the Johns Hopkins University School of Medicine.

In prior research using mice with skin transplants, Morrell and his team noted that increased platelet interactions led to increased and prolonged white cell interactions with the inner lining of the blood vessels and worsened transplant vessel damage.

“We watched platelets flowing through the blood vessels of transplanted skin in mice with and without platelets and determined tissue-platelet interactions by comparing the speeds of those flows,” says Morrell, whose team ultimately demonstrated that antibodies made in reaction to the transplanted tissue sparked platelet activation and white cell recruitment.

Studies on tissue from platelet-depleted mice helped confirm the importance of platelets in white cell activation and recruitment, strongly suggesting that limiting the inflammatory response might improve transplanted tissue survival.

Mounting evidence suggesting that platelets are activated not only post-transplant, but also during organ harvest, presents new opportunities for attacking organ injury and rejection head-on, says Rabb. The traditional target of current anti-rejection medicine is the so-called T lymphocyte — a white blood cell believed to be the major orchestrator of the immune response against any foreign tissues, including transplants.

“The thought was that if we hit the general that initiates acute rejection, it would put the troops in disarray,” says Rabb. “Traditional therapies therefore inhibit or deplete T lymphocytes and other white blood cell components of the immune system. The newest kid on the block is the platelet and it represents an opportunity to target the effectors of organ injury rather than only the general.”

The authors of the review, who were supported by National Institutes of Health grants, are A.D. Kirk, Emory Transplant Center, Emory University; W.M. Baldwin III, formerly of Johns Hopkins and now at the Lerner Research Institute; and Morrell, of Johns Hopkins.

Maryalice Yakutchik | EurekAlert!
Further information:
http://www.jhmi.edu

More articles from Life Sciences:

nachricht Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University

nachricht How herpesviruses win the footrace against the immune system
26.05.2017 | Helmholtz-Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>