To determine what antigens Tregs can recognize, Drs. Pacholczyk and Ignatowicz did side-by-side studies of antigen receptors expressed on nave T cells and Tregs.
Here, we could quantitatively compare proportions of how many regulatory cells or how many non-regulatory cells see non-self versus self antigens, and we found these proportions to be similar,? says Dr. Ignatowicz. We found regulatory cells respond to cells presenting non-self antigens as frequently as nave T cells.
Researchers report that 70 percent of the most frequent receptors found on na ve T cells also were found on Tregs. Since receptors define what the individual T cell recognizes, it provides additional evidence that nave T cells and Tregs see the same thing, they say.
Drs. Pacholczyk and Ignatowicz reported in the August 2006 issue of Immunity that Tregs, like na ve T cells, learn what to recognize in the thymus. They also reported that most Tregs that mature in the thymus retain their regulatory properties and do not later convert to nave T cells as was previously believed. This finding emphasized the role of the thymus as the primary site where Tregs differentiate and acquire their unique inhibitory functions, they say.
Although, the majority of T cells that may harm healthy body tissue are eliminated in the thymus, some errant autoreactive cells can escape and cause autoimmune disease. Tregs previously believed to primarily recognize self-tissue with the idea of protecting it are considered the antithesis of these autoreactive cells.
It was believed that regulatory cells are baptized autoreactive cells, says Dr. Ignatowicz. They are like bad boys that went good, since they also recognize self tissue but seek to protect it.
Yet scientists kept running into the reality that some regulatory cells also were recognizing and potentially protecting invaders such as bacteria and viruses.
The MCG scienti
|Contact: Toni Baker|
Medical College of Georgia