CD8A and neoplasm: ,21 Work in mouse tumor models has shown that tumor-specific exhausted progenitor CD8+ T cells are present in tumor-draining lymph nodes and that they are clonally related to tumor-infiltrating, terminally differentiated CD8+ T cells.33, 34, 35 Further, the maintenance of antigen-specific CD8+ T cells within mouse models requires the migration of lymph-node-resident progenitor cells to the tumor; intratumoral TCF-1+ tumor-specific cells are not a self-sustaining population.34