The present disclosure relates to compositions and methods for enhancing cell response and/or expanding chimeric antigen receptor (CAR) cells and/or maintenance in vivo and/or in vitro. In embodiments, the method comprises obtaining CAR T cells comprising a CAR comprising a binding domain that binds a solid tumor antigen, a transmembrane domain, and an intracellular domain; and contacting the CART cells with white blood cells and a bispecific antibody, such as a Bispecific T cell engager (BiTE®), thereby activating the CAR T cells, wherein the level of activation of the CAR T cells is higher than the level of activation of CAR T ells that are contacted with B cells without the bispecific antibody. The bispecific antibody comprises a first binding domain binding CD3 and a second binding domain binding CD19, CD20, CD22, or BCMA.