Expression of Helios, an Ikaros transcription factor family member, differentiates thymic-derived from peripherally induced Foxp3+ T regulatory cells.

Summary: Our immune system has a specialized police force called Regulatory T cells (Tregs) that prevents the body from attacking itself. Until now, scientists struggled to tell the difference between the "veteran" officers trained in the thymus (the body's main T-cell academy) and the "rookie" officers recruited directly from the bloodstream (periphery). This study identifies a protein called Helios. The researchers discovered that Helios is worn like a badge of honor exclusively by the veteran, thymus-trained cells. Those recruited in the field do not express this protein. This discovery allows doctors to distinguish between these two distinct types of immune protectors, shedding light on how our immune system balances safety and defense.