Regulatory T cells, which function like immune system police, learn early in life what to protect, and that may include viruses, bacteria and tumors, researchers have shown.
Using genetically manipulated mice and technology that enables a snapshot of the repertoire of antigen receptors that determine what cells recognize, Medical College of Georgia researchers followed T cells as they spent time in the thymus then moved to the body.
They found regulatory T cells learn what to protect while in the thymus and that everything the cells learn may not be good, according to research in the August issue of Immunity.
It is widely believed that regulatory T cells only recognize endogenous body tissue so they can stop T cells that are predisposed to attacking it, says Dr. Leszek Ignatowicz, MCG immunologist and the study's corresponding author.
By examining receptors on all types of T cells before and after they leave the thymus, researchers found regulatory T cells are very diverse and able to recognize endogenous tissue and invaders, Dr. Ignatowicz says.
Unfortunately, the cells also may not learn to recognize all endogenous tissue which, along with environmental and other factors, can lead to autoimmune disease.
T cell schooling in the thymus peaks in the first six weeks of life in the mouse, which roughly translates to the first 15 years of human life. Those early lessons seem to last a lifetime and the few regulatory cells that develop later will be like the early cells, says Dr. Rafal Pacholczyk, MCG immunologist and lead author.
The findings mean, essentially from the beginning, some people may have regulatory T cells less skilled at keeping the immune system from attacking their bodies and/or too skilled at protecting invaders.
It also means one day physicians might steer early education of regulatory T cells in the thymus as a way to vaccinate children against diseases such as lupus, arthritis and type 1diabetes. Or, they might add regulatory T cells to improve the mix in people who already have some bad police.
"We need some of the regulatory cells more than others," says Dr. Ignatowicz. "We probably need more of the ones that recognize autoantigens on the pancreas and we need the ones that recognize tumors to be less frequent."
The fact that most regulatory T cells in the body come directly from the thymus, not from other circulating T cells, also was previously unknown, Dr. Pacholczyk says. "Where they come from is the main question we wanted to answer," says Dr. Ignatowicz.