Effect of CD3δ Deficiency on Maturation of α/β and γ/δ T-Cell Lineages in Severe Combined Immunodeficiency

Three closely related infants with a form of severe combined immunodeficiency characterized by the absence of T cells but normal numbers of B cells were found to have an identical germ-line mutation in the CD3δ gene. The mutation prevented synthesis of the CD3δ protein and was associated with a block early in the development of thymocytes into mature T cells.