Role of T lymphocytes in Ad-CD40L-mediated antitumor effects against B16ova tumors. (a and b) In animals treated with intratumoral (a) adenovirus or (b) VSV, spleens were harvested on day 16 after tumor challenge, dissociated into single-cell suspensions (1 × 105 cells per well), and cultured in vitro for 48 hr in the presence of the indicated peptides. Supernatants were harvested and assayed for IFN-γ, using ELISA. Values represent averages of three spleens per group, each done in triplicate wells (means ± SEM). (c) Kaplan–Meier plot of CD8+ T cell-depleted C57BL/6 mice (n = 7 mice per group) after six intratumoral injections of adenovectors. Depleting antibodies against CD8+ T cells or control antibody (IgG isotype control) was given intraperitoneally starting on day 4 after tumor implantation and weekly thereafter. Virus was injected intratumorally starting on day 7 and given every other day for 2 weeks. (d) Kaplan–Meier plot of subcutaneous B16ova melanoma-bearing C57BL/6 mice (n = 8 mice per group) treated with intratumoral VSV-CD40L in the presence or absence of anti-CD8 depleting antibody. *p < 0.05, **p < 0.01, ***p < 0.001.