A type of lymphocyte (one of the varieties of white blood cell) that plays an important role in the immune response. The “T” stands for thymus-derived, since the thymus is the organ in which the T cells’ final stage of development occurs. Normally, T cells help the body fight infection and rid it of dead cells. In Type 1 diabetes, however, some of the T cells launch a misguided attack on the insulin-producing beta cells of the pancreas, destroying them. Researchers are exploring potential therapies for early Type 1 diabetes that involve reprogramming these T cells.