Left hand figure: Dose dependent induction of CD19 expression. CHO-K1 cells containing an inducible CD19 construct. Inducer was added at the indicated concentrations and the cells were incubated for 48 hours. CD19 expression was detected by flow cytometry analysis and the number of CD19 receptors per cell was quantified using a Quantibrite PE bead fluorescence quantification kit (BD Biosciences). The CD19 receptors per cell for Ramos, Raji (diseased) and B cells isolated from PBMCs (healthy) are shown by way of comparison.
Right hand figure: Use of CHO-K1 inducible CD19 cells for the comparison of the cytotoxicity of two CD19xCD3 bispecific T cell engagers (TCEs) across a range of CD19 receptor expression levels. CHO-K1 inducible CD19 cells were seeded in xCELLigence RTCA plates and treated with a concentration series of inducer for 24 hours to induce CD19 expression. CD8+ T cells were isolated from donor PBMCs (n=10) and incubated with target cells at a 3:1 ratio in the presence of 225pM CD19xCD3 TCE 1 or TCE 2. Target cell death, as determined by impedance loss due to cell detachment, was determined after a further 72 hours. Data show mean of donors (n=10) +/- SD.