CD4(+) CD25(+) T-cell production in healthy humans and in patients with thymic hypoplasia.

Regulatory T cells are found primarily in the CD4(+) CD25(+) fraction of T cells and play an important role in the prevention of autoimmunity. We examined CD4(+) CD25(+) T cells in 33 healthy children and adults and compared them to a population with an inherited form of thymic hypoplasia and a predisposition to autoimmune disease. Absolute numbers of CD4(+) CD25(+) T cells were markedly higher in healthy infants than in infants with chromosome 22q11.2 deletion syndrome.