Complete Absence of CD3 Protein Expression Is Responsible for Combined Immunodeficiency with Autoimmunity Rather than SCID We show for the first time that the variant leads to complete absence of protein expression while preserving polyclonal CD3 SP + sp T cell ontogenesis and less severe phenotype. Western blot analysis of CD3 demonstrated complete loss of CD3 protein expression in the patient as compared to the healthy control (Fig. In contrast, CD3 -deficient patients retain the development of polyclonal T cells (Supplementary Fig. [Extracted from the article]