Biallelic form of a known CD3E mutation in a patient with severe combined immunodeficiency
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To the Editor: T cell receptor (TCR) complex consists of αβ or γδ TCR chains in combination with four CD3 subunits, CD3ε, CD3γ, CD3δ, and CDζ . 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 . CD3 deficiencies can cause a rare form of severe combined immunodeficiency (SCID). Although CD3ε, CD3δ, and CDζ mutations usually result in a T- B+ +NK+ SCID phenotype, CD3γ deficiency leads to a milder phenotype with autoimmunity . Only 2% of patients with SCID have TCR defects . The T cell antigen receptor epsilon subunit (CD3E) gene is located at 11q23.3 and has been associated with autosomal recessive SCID . 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.