Researchers discover human immune system has emergency back-up plan

New research by scientists at the University of California, San Diego School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences, reveals that the immune system has an effective back-up plan to protect the body from infection when the ''master regulator'' of the body's innate immune system fails. 

The study appeared in the December 19 online issue of the journal Nature Immunology.

The innate immune system defends the body against infections caused by bacteria and viruses, but also causes inflammation which, when uncontrolled, can contribute to chronic illnesses such as heart disease, arthritis, type 2 diabetes and cancer.

A molecule known as nuclear factor kappa B (NF-kB) has been regarded as the ''master regulator'' of the body's innate immune response, receiving signals of injury or infection and activating genes for microbial killing and inflammation.
Led by Michael Karin, PhD, Distinguished Professor of Pharmacology, the UC San Diego team studied the immune function of laboratory mice in which genetic tools were used to block the pathway for NF-kB activation. While prevailing logic suggested these mice should be highly susceptible to bacterial infection, the researchers made the unexpected and counterintuitive discovery that NF-kB-deficient mice were able to clear bacteria that cause a skin infection even more quickly than normal mice.

''We discovered that loss of NF-kB caused mice to produce a potent immune-activating molecule known as interleukin-1 beta (IL-1b), which in turn 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.