Navigation Links
Macrophages: The 'defense' cells that help throughout the body


David Mosser, Professor of Cell Biology and Molecular Genetics at the University of Maryland's College of Chemical and Life Sciences, will discuss the three primary duties of macrophages at the 2010 American Physiological Society conference, Inflammation, Immunity, and Cardiovascular Disease, in Westminster Colorado, August 25-28. The full conference program can be found at

"There has been a huge outpouring of research about host defense that has overshadowed the many diverse activities that these cells do all the time," said Dr. Mosser. "We'd like to dispel the narrow notion that most people have that macrophages' only role is defense, and expand it to include their role in homeostasis."

Monocyte Differentiation


However, when monocytes differentiate in response to stimuli such as prostaglandins or glucocorticoids, the resulting macrophages will assume a "regulatory" phenotype. Alternately, wound-healing macrophages arise when monocytes differentiate in response to interleukin-4, a cytokine which is released during tissue injury.

According to Dr. Mosser, macrophages can change their physiology and switch types. For example, in healthy, non-obese people, macrophages in fat tend to function as wound-healing macrophages. They are also thought to maintain insulin sensitivity in adipose cells. However, should an individual become obese, macrophages in fat will instead promote inflammation and cause the adipose cells to become resistant to insulin.

Immune Regulation

Immune-regulating macrophages produce high levels of the cytokine interleukin-10, which helps suppress the body's immune response. Suppressing an immune response may seem counter-intuitive, but in the later stages of immunity it comes in handy because it limits inflammation.


There is broad potential for exploiting different stages of macrophage activation, Dr. Mosser added. "It might be possible to manipulate macrophages to make better vaccines, prevent immunosuppression, or develop novel therapeutics that promote anti-inflammatory immune responses."

Wound Healing

The release of interleukin-4 in response to tissue injury not only results in macrophages that specialize in wound-healing, it allows the macrophages to convert arginine to ornithine, which is a precursor of polyamines and collagen. Both polyamines and collagen are instrumental to the formation and maintenance of extracellular matrix, the material between cells that gives them structural support.

Certain harmful microbes, such as the tropical parasite Leishmania spp., can exploit wound-healing macrophages, said Dr. Mosser. "If you have a macrophage whose job it is to promote wound-healing, that macrophage will not be capable of killing microbes," he said. "The microbe can enter the macrophage and survive inside, which is not good for the human host."

Infection with Leishmania spp. causes leishmaniasis, which is characterized by skin sores and ulcers and can enlarge the spleen, damage the liver, and cause anemia. At worst, it can decrease immunity and leave victims vulnerable to potentially fatal opportunistic infections. Survivors can suffer from immune reconstitution inflammatory syndrome, in which their recovering immune systems go overboard in response to infection and create an inflammatory response that makes symptoms even worse. Understanding how Leishmania exploits macrophages has led to a better understanding of how macrophages function in health and disease. It has also stressed the importance of treating infections early, before the bugs can wreak havoc on the immune system.


Contact: Donna Krupa
American Physiological Society

Related biology news :

1. What causes cell defenses to crumble?
2. Researchers recreate SARS virus, open door for potential defenses against future strains
3. New dummy design and development wins US Department of Defense award
4. Lockheed Martin Team Wins Role on Key Department of Defense Biometrics Contract Vehicle
5. Raytheon Chosen to Help Provide Department of Defense Biometrics Operations and Support Services
6. ASM biodefense and emerging diseases research meeting
8. CSC Awarded Department of Defense Biometrics Contract
9. Understanding natural crop defenses
10. Reforming defense department acquisition policy: UM expert
11. Researchers discover primer to plant defense system
Post Your Comments:
Breaking Biology News(10 mins):
Breaking Biology Technology: