All TCR chains were initially believed to be necessary for efficient TCR expression at the cell surface (5) but the study of TCR immunodeficiencies (TCRID) has demonstrated that this is not the case, as some TCRID show a significant number of T cells able to express a surface TCR despite the lack of certain TCR subunits, such as CD3γ (6–8). The gene discussed is CD3G; the disease is immunodeficiency disease.