Immune system police are as good at recognizing bad guys, such as bacteria and viruses, as they are our own tissue, researchers say.

The finding may cause a stir in the scientific community, which has long held that regulatory T cells or Tregs, preferentially respond to body proteins, or self antigens, rather than non-self antigens, invaders such as viruses and bacteria.

Now, Medical College of Georgia immunologists report in the September issue of Immunity that Tregs, similarly to other T cells, respond stronger and more frequently to foreign substances than to the body's own antigens.

Fortunately, the potential conflict between naïve and regulatory T cells, in which the former lead the attack against invaders and the latter try to protect invaders, usually doesn't exist, the scientists say.

That's probably because other types of immune cells come to help T cells fight an infection, says Dr. Rafal Pacholczyk, a corresponding author for the study.

"During the normal immune response, Tregs sit in the back seat and, in most cases, don't interfere," says Dr. Leszek Ignatowicz, also a corresponding author.

Still, emerging therapies to fight autoimmune diseases, such as arthritis, multiple sclerosis and type 1 diabetes, by boosting the total number of Tregs could unintentionally upset the balance between naïve T cells and Tregs, they say.

"Regulatory cells always suppress immunity…