Fig. 2.

Systematic engagement of accessory receptors identifies that CARs are inefficient at exploiting the adhesion receptors CD2 and LFA-1 relative to the TCR. (A) Schematic of accessory receptors and their ligands. (B and C) Representative dose–response curves showing T cell activation by upregulation of surface CD69 measured by flow cytometry after 24 h using the solid-phase stimulation assay. T cells were presented with purified pMHC alone (“None”) or with a fixed concentration of 250 ng/well of the indicated accessory receptor ligand (colors) for the (B) TCR and (C) the indicated CARs. (D) The EC₅₀values for the indicated antigen receptor and purified ligand condition were obtained by fitting a Hill function to each dose–response curve. Individual EC₅₀values for each antigen receptor are from an independent experiment (N ≥ 3). The numbers indicate the fold-change in EC₅₀induced by the accessory receptor ligand relative to pMHC alone (“None”), and statistical significance is determined by a paired t-test on log-transformed data. (E) The data in (D) are presented in a different format showing the fold-change in EC₅₀between the TCR and the indicated CAR for pMHC alone or the indicated accessory receptor ligand. The fold-change is compared using a one-sample t-test to a hypothetical value of 0 on log-transformed data. *P-value ≤ 0.05, **P-value ≤ 0.01, ***P-value ≤ 0.001, ****P-value ≤ 0.0001.