Erman, BaranFırtına, SinemFışgın, TunçBozkurt, CeyhunCipe, Funda Erol2021-05-152021-05-1520200271-91421573-2592https://doi.org/10.1007/s10875-020-00752-3https://hdl.handle.net/20.500.12939/243FIRTINA, Sinem/0000-0002-3370-8545; BOZKURT, CEYHUN/0000-0001-6771-9894; Erman, Baran/0000-0001-9398-8465To 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 [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 CD3ε, CD3δ, and CDζ mutations usually result in a T- B+ +NK+ SCID phenotype, CD3γ 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.eninfo:eu-repo/semantics/closedAccessPrimary ImmunodeficiencySevere Combined ImmunodeficiencyCD3 Epsilon DeficiencyLetter10.1007/s10875-020-00752-3403539542320166512-s2.0-85078999106Q1WOS:000515758800001Q1