February 27, 2020

A study led by Lupus Research Alliance grantee Dr. J. Michelle Kahlenberg of the University of Michigan has revealed one reason why people with lupus tend to get rashes. Dr. Kahlenberg and her team found that certain immune system molecules produced by people with lupus help bacteria gain a foothold on the skin, where they can trigger inflammation.

Rashes are one of the most common symptoms of lupus. People with the disease also often have higher-than-normal levels of the immune system molecules called type I interferons, which usually help the body fight off infections but cause damage in lupus.

Dr. Kahlenberg and her team identified a connection between type I interferons and the development of the lupus rash.  They discovered that type I interferons help a type of bacteria called Staphylococcus aureus, stick to skin cells. Dr. Kahlenberg’s team also found that people with lupus are more likely to have this type of bacteria living on their skin than are people without the disease.

Type I interferons may also help Staphylococcus aureus slip through the outer layer of skin that normally blocks it from entering the body. The researchers found that when skin cells are stimulated by type I interferons, the cells make less of certain proteins that enable the skin to form a solid barrier.

When the outer layer of skin breaks down, more bacteria can grow on the skin. But skin cells try to fight them off by releasing more type I interferons. Dr. Kahlenberg and her team suggest the bacteria may set off a vicious circle in which skin cells make more type I interferons that in turn weaken the skin’s defenses and allow more bacteria to live on the skin, producing the rash so often seen with lupus. The team concluded that more research into how to restore the outer layer of the skin might help discover new treatments for the lupus rash.  The study was published in the Journal of Investigative Dermatology.