TCR and CAR. TCR αβ subunits combine with γ, δ, ε, and ζ subunits of the CD3 to form the multisubunit TCR complex. Peptide-HLA binding to the TCR αβ combined with the other subunits and with either CD4 or CD8 coreceptor initiates downstream signaling, T-cell activation, and effector functioning. Proteins involved in signaling such as LCK and ZAP70 are indicated and the activating motifs within the subunits are represented as horizontal bars. A typical CAR molecule comprises an antigen-specific scFv from a monoclonal antibody linked to a spacer, costimulatory domain (CD28 or 4-1BB shown in this example) and signaling CD3ζ domain. Figure created with BioRender.com: Gore S. (2025); https://BioRender.com/o91f055