Biallelic form of a known CD3E mutation in a patient with severe combined immunodeficiency

T cell receptor (TCR) complex consists of ?? or ?? TCR chains in combination with four CD3 subunits, CD3?, CD3?, CD3?, and CD? [1]. This complex is required for thymocyte development and the initiation of T cell-mediated adaptive immune responses. Although TCR chains bind antigenic peptides presented by MHC molecules, the CD3 subunits provide transduction of signals into the cytosol for the activation and differentiation of T lymphocytes [2]. CD3 deficiencies can cause a rare form of severe combined immunodeficiency (SCID). Although CD3?, CD3?, and CD? mutations usually result in a T- B+ +NK+ SCID phenotype, CD3? deficiency leads to a milder phenotype with autoimmunity [3]. Only 2% of patients with SCID have TCR defects [3]. The T cell antigen receptor epsilon subunit (CD3E) gene is located at 11q23.3 and has been associated with autosomal recessive SCID [4]. Only a few mutations of the CD3E gene have been identified so far [4–8]. Here, we identified the biallelic form of a known CD3E mutation in a patient with a severe T- B+ NK+ phenotype