CD3G or CD3D Knockdown in Mature, but Not Immature, T Lymphocytes Similarly Cripples the Human TCRαβ Complex

• DOI: 10.3389/fcell.2021.608490
• Publication Date: 2021-06-25T07:39:10Z
• Authors: Beatriz Garcillán; Patricia Fuentes; Ana V. Marin; Rebeca F. Megino; Daniel Chacon-Arg...; Marina S. Mazariegos; Anaïs Jiménez-Rei...; Miguel Muñoz-Ruiz; Raquel G. Laborda; Paula P. Cárdenas; Edgar Fernández-M...; Maria L. Toribio; José R. Regueiro
• Keywords: 0303 health sciences; QH301-705.5; Medicina; TCR assembly; T-cell receptor (TCR); CD3D; T-cell progenitors; Oncología; CD3G; 3. Good health; 3201.01 Oncología; Cell and Developmental Biology; 03 medical and health sciences; 32 Ciencias Médicas; Immunodeficiency; shRNA knockdown; Biology (General); immunodeficiency

The human αβ T-cell receptor (TCR) is composed of a variable heterodimer (TCRαβ) and three invariant dimers (CD3γε, CD3δε, and ζζ/CD2472). The role of each invariant chain in the stepwise interactions among TCR chains along the assembly is still not fully understood. Despite the high sequence homology between CD3γ and CD3δ, the clinical consequences of the corresponding immunodeficiencies (ID) in humans are very different (mild and severe, respectively), and mouse models do not recapitulate findings in human ID. To try to understand such disparities, we stably knocked down (KD)CD3DorCD3Gexpression in the human Jurkat T-cell line and analyzed comparatively their impact on TCRαβ assembly, transport, and surface expression. The results indicated that TCR ensembles were less stable and CD3ε levels were lower when CD3γ, rather than CD3δ, was scarce. However, both defective TCR ensembles were strongly retained in the ER, lacked ζζ/CD2472, and barely reached the T-cell surface (<11% of normal controls) in any of theCD3KD cells. This is in sharp contrast to human CD3γ ID, whose mature T cells express higher levels of surface TCR (>30% vs. normal controls).CD3KD of human T-cell progenitors followed by mouse fetal thymus organ cultures showed high plasticity in emerging immature polyclonal T lymphocytes that allowed for the expression of significant TCR levels which may then signal for survival in CD3γ, but not in CD3δ deficiency, and explain the immunological and clinical disparities of such ID cases.