"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 Professor Dr David Mosser of the University of Maryland's College of Chemical and Life Sciences.

"We'd like to dispel the narrow notion that most people have that macrophages' only role is defence, and expand it to include their role in homeostasis."

"It might be possible to manipulate macrophages to make better vaccines, prevent immunosuppression, or develop novel therapeutics that promote anti-inflammatory immune responses."

But 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."

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.