The research offers a new perspective on a component of the immune system known as the acute-phase response, a series of systemic changes in blood protein levels, metabolic function, and physiology that sometimes occurs when bacteria, viruses, or other pathogens invade the body. This response puts healthy cells and tissue under serious stress, and is actually the cause of many of the symptoms we associate with being sick.
"The question is why would these harmful components evolve," asks Edmund LeGrand (University of Tennessee, Knoxville), who wrote the paper titled with Joe Alcock (University of New Mexico). The researchers contend that answer becomes clear when we view the acute-phase response in terms of what they call "immune brinksmanship."
The immune brinksmanship model "is the gamble that systemic stressors will harm the pathogens relatively more than the host," LeGrand said. The concept, he explains, is akin to what happens in international trade disputes. When one country places trade sanctions on another, both countries' economies take a hit, but the sanctioning country is betting that its opponent will be hurt more.
"One of our contributions here is to pull together the reasons why pathogens suffer more from systemic stress," LeGrand said.
The acute-phase response creates stress in several ways. It raises body temperature and causes loss of appetite and mild anemia. At the same time, certain vital nutrients like iron, zinc, and manganese are partially sequestered away from the bloodstream.
Some of these components are quite puzzling. Why reduce food intake just when one would expect more energy would be needed to mount a strong immune response? Zinc is essential for healthy immune function. Why pull it out of the bloodstream when the immune system is active? The benefits of a stressor like fever are fairly well known; heat has been shown to inhibit bacterial growth and cause infected cells to self-destruct. But what hasn't been clear is why pathogens should be more susceptible to this stress than the host.
LeGrand and Alcock offer some answers. For an infection to spread, pathogens need to multiply, whereas host cells can defer replication. Replication makes DNA and newly forming proteins much more susceptible to damage. It also requires energy and nutrients—which helps explain the benefits of restricting food and sequestering nutrients.
The act of invading a body also requires bacteria to alter their metabolism, which can make them more vulnerable to all kinds of stress, including heat.
Another reason pathogens are more vulnerable to stress is that the immune system is already pummeling them with white blood cells and related stressors at the site of the infection. That means that pathogens are already under local stress when systemic stressors are piled on. "In many ways, the acute-phase response reinforces the stress inflicted on pathogens locally at the infection site," LeGrand said.
As the term "brinksmanship" implies, there's an inherent risk in a strategy that involves harming oneself to hurt the enemy within. This self-harm leaves the body more vulnerable to other dangers, including other infections. Additionally, it is possible for the immune stressors to do more damage than required to control the pathogens.
"But in general, systemic stressors when properly regulated do preferential harm to invaders," LeGrand said. Viewed this way, it's not surprising that natural selection has utilized the stressful parts of the acute-phase response in mammals, reptiles, fish, and even invertebrates.
Edmund LeGrand and Joe Alcock, "Turning Up The Heat: Immune Brinksmanship In The Acute-phase Response." The Quarterly Review of Biology 87:1 (March 2012).
The premier review journal in biology since 1926, The Quarterly Review of Biology publishes articles in all areas of biology but with a traditional emphasis on evolution, ecology, and organismal biology. QRB papers do not merely summarize a topic, but offer important new ideas, concepts, and syntheses. They often shape the course of future research within a field. In addition, the book review section of the QRB is the most comprehensive in biology.
Kevin Stacey | EurekAlert!
Fine organic particles in the atmosphere are more often solid glass beads than liquid oil droplets
21.04.2017 | Max-Planck-Institut für Chemie
Study overturns seminal research about the developing nervous system
21.04.2017 | University of California - Los Angeles Health Sciences
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...
Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.
A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
21.04.2017 | Physics and Astronomy
21.04.2017 | Health and Medicine
21.04.2017 | Physics and Astronomy