CD28 and hepatocellular carcinoma: CD4+ naïve T cells were isolated from C57BL/6 mouse spleens, activated with anti‐CD3/CD28 magnetic beads in the presence of interleukin (IL)‐2, and then co‐cultured with the murine HCC cell line Hepa53.4 to recapitulate the TME (Figure S4E, Supporting Information).