Our immune system has back-up to fight infection

Our immune system protects the body against infections caused by bugs and viruses, but also causes inflammation which, when uncontrolled, can trigger chronic illnesses such as heart disease, arthritis, type-2 diabetes and cancer, reports the journal Nature Immunology.

A molecule known as nuclear factor kappa B (NF-κB) has been regarded as the "master switch" of the body's immune response, receiving signals of injury or infection and activating genes for microbial killing and inflammation.

Michael Karin, professor of pharmacology at the University of California, San Diego, led a team to study the immune function of lab mice which were genetically deprived of the NF-κB molecule, according to a California statement.

While prevailing logic suggested these mice should be susceptible to bacterial infection, researchers made the unexpected discovery that NF-κB-deficient mice were able to clear bugs that cause a skin infection even more quickly than normal mice.

"We discovered that loss of NF-κB caused mice to produce a potent immune-activating molecule known as interleukin-1 beta (IL-1β), which stimulated their bone marrow to produce dramatically increased numbers of white blood cells known as neutrophils," said Karin.

Neutrophils are the body's front-line defenders against infection, capable of swallowing and killing bacteria with a variety of natural antibiotic enzymes and proteases.

The new research demonstrates that the innate immune system deploys two effective strategies to deal with invasive bacterial infection, and that the IL-1β system provides an important safety net when NF-κB falls short.

"Having a backup system in place is critical given the diverse strategies that bacterial pathogens have evolved to avoid bacterial clearance," said Victor Nizet, professor of pediatrics and pharmacy, whose lab conducted the infectious challenge experiments in the study.