CD4⁺ T cells are required for SA-4-1BBL/TAAs vaccine-induced long-term immune memory against 3LL, but not against TC-1 tumor.

<p>(A) Schematic depiction of the experimental procedure. (B) Long-term C57BL/6 mice that had eradicated TC-1 tumors irrespective of CD4+ T cell depletion one day before vaccination with SA-4-1BBL/E7 had long-term protective immune response as assessed by a secondary challenge with TC-1 tumor cells 60 days after the initial tumor inoculation. Naïve mice injected with PBS and challenged with 1×10⁵ TC-1 cells served as controls and expired from tumor burden within 40 days. (C) Long-term C57BL/6 mice that had eradicated 3LL tumors irrespective of CD4+ T cell depletion one day before vaccination with SA-4-1BBL/SVN had significantly compromised memory immune response as assessed by a secondary challenge with 3LL tumor cells 60 days after the initial tumor inoculation. Naïve mice injected with PBS and challenged with 1×10⁵ 3LL cells served as controls and expired from tumor burden within 50 days.