CD28 and neoplasm: Another strategy circumvents the necessity of endosome escaping and achieves effective T cells activation and tumor eradication by engineering aAPCs based on modification of nanosized particles, including magnetic beads,187 liposomes,188 polymer nanoparticles,19 and paramagnetic nanoparticles.189 The aAPCs basically contain two signals for T cell activation, that is, MHCI‐antigen complex and a costimulatory signal, such as anti‐CD28 and anti‐CD3 Abs.190, 191 They can be either intravenously injected in vivo or used in ACT ex vivo.