To confirm the role of Id2 in antigen-specific CD8+ T-cell activity, we adoptively transferred CD8+ T cells sorted from Id2fl/flCd4-Cre+ OT-I mice and their Id2fl/flCd4-Cre− OT-I littermates into B16-OVA tumor-bearing B6.SJL (CD45.1) mice and then tracked and detected donor and host T cells based on the congenic markers CD45.2 and CD45.1, respectively (Fig. 4A). Here, ID2 is linked to neoplasm.