Inherited and Somatic CD3[zeta] Mutations in a Patient with T-Cell Deficiency

A four-month-old boy with primary immunodeficiency was found to have a homozygous germ-line mutation of the gene encoding the CD3ζ subunit of the T-cell receptor-CD3 complex. CD3ζ is necessary for the development and function of T cells. Some of the patient's T cells had low levels of the T-cell receptor-CD3 complex and carried the Q70X mutation in both alleles of CD3 ζ, whereas other T cells had normal levels of the complex and bore the Q70X mutation on only one allele of CD3 ζ, plus one of three heterozygous somatic mutations of CD3 ζ on the other allele, allowing expression of poorly functional T-cell receptor-CD3 complexes.