To determine how A2BR deletion affects tumor-specific CD8+ T cell responses in vivo upon α4-1BB treatment, preactivated OT-1 WT (CD90.1+) and A2BR–/– (CD90.2+) CD8+ T cells congenic for CD45.2 were mixed at a 1:1 ratio and cotransferred into LLC1-Ova tumor–bearing recipients (CD45.1+) followed with or without α4-1BB treatment. The gene discussed is CD8A; the disease is neoplasm.