IFNG and neoplasm: Although the tumor lytic capacity was similar for the three spacer variants, the short spacer CAR induced the most robust effector cytokine production upon tumor recognition, with 4.6- (P < 0.0001), 3.8- (P < 0.0001), and 3.1-fold (P=0.0001) higher IL-2, IFNg, and TNFa levels, respectively, compared to long spacer; and 2.2- (P > 0.05), 1.2- (P < 0.01) and 1.9-fold (P < 0.0001) higher IL-2, IFNg, and TNFa levels compared to medium spacer CAR (Figure 1F).