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!
Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University
How herpesviruses win the footrace against the immune system
26.05.2017 | Helmholtz-Zentrum für Infektionsforschung
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....
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....
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...
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...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy