CD19 and glioblastoma: To determine whether the PD1 minibodies secreted by ARMed EGFRvIII CAR T cells function in vivo to rescue PD1-PDL1 inhibited T cell function and improve CAR T therapy, we repeated the previous in vivo NSG xenograft flank model of GBM, this time using anti-PD1 ARMed EGFRvIII CAR T, EGFRvIII CAR T alone, or negative control CD19 CAR T cells to treat U87vIII GBM, naturally expressing high levels of PDL1, which further increased upon exposure to IFNγ (Supplementary Figure S4A).